Rework XML Element hierarchy and XmlStringBuilder

- Reduce the amount of types that are subtypes of NamedElement. See
javadoc of NamedElement for rationale.
- Work more with XmlEnvironment in XmlStringBuilder.
- Some minor changes to XmlStringBuilder API.

smack-core/src/main/java/org/jivesoftware/smack/packet/AbstractError.java

@@ -114,9 +114,7 @@ public class AbstractError {
             xml.escape(text);
             xml.closeElement("text");
         }
-        for (ExtensionElement packetExtension : extensions) {
+        xml.append(extensions);
-            xml.append(packetExtension.toXML());
-        }
     }
 
     public abstract static class Builder<B extends Builder<B>> {

smack-core/src/main/java/org/jivesoftware/smack/packet/AbstractTextElement.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2017 Florian Schmaus
+ * Copyright © 2017-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,8 +38,7 @@ public abstract class AbstractTextElement implements ExtensionElement {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
-        xml.optXmlLangAttribute(lang);
         xml.rightAngleBracket();
         xml.escape(text);
         xml.closeElement(this);
@@ -50,6 +49,19 @@ public abstract class AbstractTextElement implements ExtensionElement {
         return text;
     }
 
+    @Override
+    public final String getLanguage() {
+        return lang;
+    }
+
+    /**
+     * Deprecated.
+     *
+     * @return deprecated
+     * @deprecated use {@link #getLanguage()} instead.
+     */
+    @Deprecated
+    // TODO: Remove in Smack 4.5.
     public final String getLang() {
         return lang;
     }

smack-core/src/main/java/org/jivesoftware/smack/packet/FullyQualifiedElement.java

@@ -32,4 +32,13 @@ public interface FullyQualifiedElement extends NamedElement {
         String localPart = getElementName();
         return new QName(namespaceURI, localPart);
     }
+
+    /**
+     * Returns the xml:lang of this XML element, or null if one has not been set.
+     *
+     * @return the xml:lang of this XML element, or null.
+     */
+    default String getLanguage() {
+        return null;
+    }
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/IQ.java

@@ -136,6 +136,11 @@ public abstract class IQ extends Stanza {
         return childElementNamespace;
     }
 
+    @Override
+    public final String getElementName() {
+        return IQ_ELEMENT;
+    }
+
     @Override
     public final String toString() {
             StringBuilder sb = new StringBuilder();
@@ -150,9 +155,8 @@ public abstract class IQ extends Stanza {
 
     @Override
     public final XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
-        XmlStringBuilder buf = new XmlStringBuilder(enclosingXmlEnvironment);
+        XmlStringBuilder buf = new XmlStringBuilder(this, enclosingXmlEnvironment);
-        buf.halfOpenElement(IQ_ELEMENT);
+        addCommonAttributes(buf);
-        addCommonAttributes(buf, enclosingXmlEnvironment);
         if (type == null) {
             buf.attribute("type", "get");
         }
@@ -160,7 +164,7 @@ public abstract class IQ extends Stanza {
             buf.attribute("type", type.toString());
         }
         buf.rightAngleBracket();
-        buf.append(getChildElementXML(enclosingXmlEnvironment));
+        appendInnerXml(buf);
         buf.closeElement(IQ_ELEMENT);
         return buf;
     }
@@ -171,44 +175,52 @@ public abstract class IQ extends Stanza {
      *
      * @return the child element section of the IQ XML.
      */
+    // TODO: This method should not be part of the public API as it is mostly used for testing purposes, with the one
+    // exception of AdHocCommand.getRaw().
     public final XmlStringBuilder getChildElementXML() {
-        return getChildElementXML(null);
+        XmlStringBuilder xml = new XmlStringBuilder();
+        appendInnerXml(xml);
+        return xml;
     }
 
     /**
-     * Returns the sub-element XML section of the IQ packet, or the empty String if there
+     * Append the sub-element XML section of the IQ stanza.
-     * isn't one.
      *
-     * @param enclosingXmlEnvironment the enclosing XML namespace.
+     * @param xml the XmlStringBuilder to append to.
-     * @return the child element section of the IQ XML.
-     * @since 4.3.0
      */
-    public final XmlStringBuilder getChildElementXML(XmlEnvironment enclosingXmlEnvironment) {
+    private void appendInnerXml(XmlStringBuilder xml) {
-        XmlStringBuilder xml = new XmlStringBuilder();
         if (type == Type.error) {
             // Add the error sub-packet, if there is one.
-            appendErrorIfExists(xml, enclosingXmlEnvironment);
+            appendErrorIfExists(xml);
+            return;
+        }
+        if (childElementName == null) {
+            return;
         }
-        else if (childElementName != null) {
-            // Add the query section if there is one.
-            IQChildElementXmlStringBuilder iqChildElement = getIQChildElementBuilder(new IQChildElementXmlStringBuilder(this));
-            if (iqChildElement != null) {
-                xml.append(iqChildElement);
 
-                List<ExtensionElement> extensionsXml = getExtensions();
+        // Add the query section if there is one.
-                if (iqChildElement.isEmptyElement) {
+        IQChildElementXmlStringBuilder iqChildElement = getIQChildElementBuilder(
-                    if (extensionsXml.isEmpty()) {
+                        new IQChildElementXmlStringBuilder(this));
-                         xml.closeEmptyElement();
+        // TOOD: Document the cases where iqChildElement is null but childElementName not. And if there are none, change
-                         return xml;
+        // the logic.
-                    } else {
+        if (iqChildElement == null) {
-                        xml.rightAngleBracket();
+            return;
-                    }
-                }
-                xml.append(extensionsXml);
-                xml.closeElement(iqChildElement.element);
-            }
         }
-        return xml;
+
+        xml.append(iqChildElement);
+
+        List<ExtensionElement> extensionsXml = getExtensions();
+        if (iqChildElement.isEmptyElement) {
+            if (extensionsXml.isEmpty()) {
+                xml.closeEmptyElement();
+                return;
+            }
+
+            xml.rightAngleBracket();
+        }
+
+        xml.append(extensionsXml);
+        xml.closeElement(iqChildElement.element);
     }
 
     /**

smack-core/src/main/java/org/jivesoftware/smack/packet/Message.java

@@ -467,6 +467,11 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
         return language;
     }
 
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
@@ -481,9 +486,8 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
 
     @Override
     public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
-        XmlStringBuilder buf = new XmlStringBuilder(enclosingXmlEnvironment);
+        XmlStringBuilder buf = new XmlStringBuilder(this, enclosingXmlEnvironment);
-        buf.halfOpenElement(ELEMENT);
+        addCommonAttributes(buf);
-        enclosingXmlEnvironment = addCommonAttributes(buf, enclosingXmlEnvironment);
         buf.optAttribute("type", type);
         buf.rightAngleBracket();
 
@@ -497,16 +501,16 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
             // Skip the default language
             if (subject.equals(defaultSubject))
                 continue;
-            buf.append(subject.toXML());
+            buf.append(subject);
         }
         buf.optElement("thread", thread);
         // Append the error subpacket if the message type is an error.
         if (type == Type.error) {
-            appendErrorIfExists(buf, enclosingXmlEnvironment);
+            appendErrorIfExists(buf);
         }
 
         // Add extension elements, if any are defined.
-        buf.append(getExtensions(), enclosingXmlEnvironment);
+        buf.append(getExtensions());
 
         buf.closeElement(ELEMENT);
         return buf;
@@ -544,11 +548,7 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
             this.subject = subject;
         }
 
-        /**
+        @Override
-         * Returns the language of this message subject.
-         *
-         * @return the language of this message subject.
-         */
         public String getLanguage() {
             return language;
         }
@@ -592,8 +592,8 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder();
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
-            xml.halfOpenElement(getElementName()).optXmlLangAttribute(getLanguage()).rightAngleBracket();
+            xml.rightAngleBracket();
             xml.escape(subject);
             xml.closeElement(getElementName());
             return xml;
@@ -642,12 +642,7 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
             this.namespace = Objects.requireNonNull(namespace);
         }
 
-        /**
+        @Override
-         * Returns the language of this message body or {@code null} if the body extension element does not explicitly
-         * set a language, but instead inherits it from the outer element (usually a {@link Message} stanza).
-         *
-         * @return the language of this message body or {@code null}.
-         */
         public String getLanguage() {
             return language;
         }
@@ -692,7 +687,7 @@ public final class Message extends Stanza implements TypedCloneable<Message> {
         @Override
         public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
             XmlStringBuilder xml = new XmlStringBuilder(this, enclosingXmlEnvironment);
-            xml.optXmlLangAttribute(getLanguage()).rightAngleBracket();
+            xml.rightAngleBracket();
             xml.escape(message);
             xml.closeElement(getElementName());
             return xml;

smack-core/src/main/java/org/jivesoftware/smack/packet/NamedElement.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2014 Florian Schmaus
+ * Copyright © 2014-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,13 @@
 package org.jivesoftware.smack.packet;
 
 /**
- * Interface to represent a XML element. This is similar to {@link ExtensionElement}, but does not
+ * Interface to represent a XML element. This is similar to {@link ExtensionElement}, but does not carry a single
- * carry a namespace and is usually included as child element of an stanza extension.
+ * namespace, but instead is used with multiple namespaces. Examples for this include MUC's <destroy/> element.
+ * <p>
+ * Please note that usage of this interface is <b>discouraged</b>. The reason is that every XML element is fully
+ * qualified, i.e., it is qualified by a namespace. The namespace may not be explicitly given, but instead, is inherited
+ * from an outer element. Use {@link FullyQualifiedElement} instead when possible.
+ * </p>
  */
 public interface NamedElement extends Element {
 

smack-core/src/main/java/org/jivesoftware/smack/packet/Nonza.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2014-2015 Florian Schmaus
+ * Copyright © 2014-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,6 @@ package org.jivesoftware.smack.packet;
  * @author Florian Schmaus
  * @see <a href="http://xmpp.org/extensions/xep-0360.html">XEP-0360: Nonzas (are not Stanzas)</a>
  */
-public interface Nonza extends TopLevelStreamElement, FullyQualifiedElement {
+public interface Nonza extends TopLevelStreamElement {
 
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/Packet.java

@@ -113,11 +113,7 @@ public interface Packet extends TopLevelStreamElement {
      */
     void setError(StanzaError error);
 
-    /**
+    @Override
-     * Returns the xml:lang of this Stanza, or null if one has not been set.
-     *
-     * @return the xml:lang of this Stanza, or null.
-     */
     String getLanguage();
 
     /**

smack-core/src/main/java/org/jivesoftware/smack/packet/Presence.java

@@ -256,6 +256,11 @@ public final class Presence extends Stanza implements TypedCloneable<Presence> {
         this.mode = mode;
     }
 
+    @Override
+    public String getElementName() {
+        return ELEMENT;
+    }
+
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
@@ -277,9 +282,8 @@ public final class Presence extends Stanza implements TypedCloneable<Presence> {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder buf = new XmlStringBuilder(enclosingNamespace);
+        XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
-        buf.halfOpenElement(ELEMENT);
+        addCommonAttributes(buf);
-        addCommonAttributes(buf, enclosingNamespace);
         if (type != Type.available) {
             buf.attribute("type", type);
         }
@@ -291,10 +295,10 @@ public final class Presence extends Stanza implements TypedCloneable<Presence> {
             buf.element("show", mode);
         }
 
-        buf.append(getExtensions(), enclosingNamespace);
+        buf.append(getExtensions());
 
         // Add the error sub-packet, if there is one.
-        appendErrorIfExists(buf, enclosingNamespace);
+        appendErrorIfExists(buf);
 
         buf.closeElement(ELEMENT);
 

smack-core/src/main/java/org/jivesoftware/smack/packet/Stanza.java

@@ -59,6 +59,10 @@ public abstract class Stanza implements TopLevelStreamElement {
 
     private final MultiMap<QName, ExtensionElement> extensionElements = new MultiMap<>();
 
+    // Assume that all stanzas Smack handles are in the client namespace, since Smack is an XMPP client library. We can
+    // change this behavior later if it is required.
+    private final String namespace = StreamOpen.CLIENT_NAMESPACE;
+
     private String id = null;
     private Jid to;
     private Jid from;
@@ -283,11 +287,7 @@ public abstract class Stanza implements TopLevelStreamElement {
         error = xmppErrorBuilder.build();
     }
 
-    /**
+    @Override
-     * Returns the xml:lang of this Stanza, or null if one has not been set.
-     *
-     * @return the xml:lang of this Stanza, or null.
-     */
     public String getLanguage() {
         return language;
     }
@@ -491,6 +491,11 @@ public abstract class Stanza implements TopLevelStreamElement {
     @Override
     public abstract String toString();
 
+    @Override
+    public final String getNamespace() {
+        return namespace;
+    }
+
     /**
      * Returns the default language used for all messages containing localized content.
      *
@@ -501,33 +506,14 @@ public abstract class Stanza implements TopLevelStreamElement {
     }
 
     /**
-     * Add to, from, id and 'xml:lang' attributes
+     * Add to, from, and id attributes.
      *
      * @param xml the {@link XmlStringBuilder}.
-     * @param enclosingXmlEnvironment the enclosing XML namespace.
-     * @return the XML environment for this stanza.
      */
-    protected XmlEnvironment addCommonAttributes(XmlStringBuilder xml, XmlEnvironment enclosingXmlEnvironment) {
+    protected final void addCommonAttributes(XmlStringBuilder xml) {
-        String language = getLanguage();
-        String namespace = StreamOpen.CLIENT_NAMESPACE;
-        if (enclosingXmlEnvironment != null) {
-            String effectiveEnclosingNamespace = enclosingXmlEnvironment.getEffectiveNamespaceOrUse(namespace);
-            switch (effectiveEnclosingNamespace) {
-            case StreamOpen.CLIENT_NAMESPACE:
-            case StreamOpen.SERVER_NAMESPACE:
-                break;
-            default:
-                namespace = effectiveEnclosingNamespace;
-            }
-        }
-
-        xml.xmlnsAttribute(namespace);
         xml.optAttribute("to", getTo());
         xml.optAttribute("from", getFrom());
         xml.optAttribute("id", getStanzaId());
-        xml.xmllangAttribute(language);
-
-        return new XmlEnvironment(namespace, language);
     }
 
     protected void logCommonAttributes(StringBuilder sb) {
@@ -546,12 +532,11 @@ public abstract class Stanza implements TopLevelStreamElement {
      * Append an XMPPError is this stanza has one set.
      *
      * @param xml the XmlStringBuilder to append the error to.
-     * @param enclosingXmlEnvironment the enclosing XML environment.
      */
-    protected void appendErrorIfExists(XmlStringBuilder xml, XmlEnvironment enclosingXmlEnvironment) {
+    protected void appendErrorIfExists(XmlStringBuilder xml) {
         StanzaError error = getError();
         if (error != null) {
-            xml.append(error.toXML(enclosingXmlEnvironment));
+            xml.append(error);
         }
     }
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/TopLevelStreamElement.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2014-2018 Florian Schmaus
+ * Copyright © 2014-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,6 @@ package org.jivesoftware.smack.packet;
  * A XMPP top level stream element. This is either a stanza ({@link Stanza}) or
  * just a plain stream element ({@link Nonza}).
  */
-public interface TopLevelStreamElement extends Element {
+public interface TopLevelStreamElement extends FullyQualifiedElement {
 
 }

smack-core/src/main/java/org/jivesoftware/smack/packet/XmlEnvironment.java

@@ -106,6 +106,29 @@ public class XmlEnvironment {
         return effectiveLanguage;
     }
 
+    public boolean effectiveLanguageEquals(String language) {
+        String effectiveLanguage = getEffectiveLanguage();
+        if (effectiveLanguage == null) {
+            return false;
+        }
+        return effectiveLanguage.equals(language);
+    }
+
+    private transient String toStringCache;
+
+    @Override
+    public String toString() {
+        if (toStringCache == null) {
+            StringBuilder sb = new StringBuilder();
+            sb.append(XmlEnvironment.class.getSimpleName()).append(' ');
+            sb.append("xmlns=").append(getEffectiveNamespace()).append(' ');
+            sb.append("xmllang=").append(getEffectiveLanguage()).append(' ');
+
+            toStringCache = sb.toString();
+        }
+        return toStringCache;
+    }
+
     public static XmlEnvironment from(XmlPullParser parser) {
         return from(parser, null);
     }

smack-core/src/main/java/org/jivesoftware/smack/util/XmlStringBuilder.java

@@ -38,17 +38,12 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
     private final XmlEnvironment effectiveXmlEnvironment;
 
     public XmlStringBuilder() {
-        this((XmlEnvironment) null);
-    }
-
-    public XmlStringBuilder(XmlEnvironment effectiveXmlEnvironment) {
         sb = new LazyStringBuilder();
-        this.effectiveXmlEnvironment = effectiveXmlEnvironment;
+        effectiveXmlEnvironment = null;
     }
 
     public XmlStringBuilder(ExtensionElement pe) {
-        this();
+        this(pe, null);
-        prelude(pe);
     }
 
     public XmlStringBuilder(NamedElement e) {
@@ -59,12 +54,24 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
     public XmlStringBuilder(FullyQualifiedElement element, XmlEnvironment enclosingXmlEnvironment) {
         sb = new LazyStringBuilder();
         halfOpenElement(element);
-        if (enclosingXmlEnvironment != null
+
-                && !enclosingXmlEnvironment.effectiveNamespaceEquals(element.getNamespace())) {
+        String xmlNs = element.getNamespace();
-            xmlnsAttribute(element.getNamespace());
+        String xmlLang = element.getLanguage();
+        if (enclosingXmlEnvironment == null) {
+            xmlnsAttribute(xmlNs);
+            xmllangAttribute(xmlLang);
+        } else {
+            if (!enclosingXmlEnvironment.effectiveNamespaceEquals(xmlNs)) {
+                xmlnsAttribute(xmlNs);
+            }
+            if (!enclosingXmlEnvironment.effectiveLanguageEquals(xmlLang)) {
+                xmllangAttribute(xmlLang);
+            }
         }
+
         effectiveXmlEnvironment = XmlEnvironment.builder()
-                .withNamespace(element.getNamespace())
+                .withNamespace(xmlNs)
+                .withLanguage(xmlLang)
                 .withNext(enclosingXmlEnvironment)
                 .build();
     }
@@ -124,6 +131,15 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
         return this;
     }
 
+    /**
+     * Deprecated.
+     *
+     * @param element deprecated.
+     * @return deprecated.
+     * @deprecated use {@link #append(Element)} instead.
+     */
+    @Deprecated
+    // TODO: Remove in Smack 4.5.
     public XmlStringBuilder element(Element element) {
         assert element != null;
         return append(element.toXML());
@@ -161,7 +177,7 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
 
     public XmlStringBuilder optElement(Element element) {
         if (element != null) {
-            append(element.toXML());
+            append(element);
         }
         return this;
     }
@@ -435,6 +451,7 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
     }
 
     public XmlStringBuilder xmllangAttribute(String value) {
+        // TODO: This should probably be attribute(), not optAttribute().
         optAttribute("xml:lang", value);
         return this;
     }
@@ -499,13 +516,13 @@ public class XmlStringBuilder implements Appendable, CharSequence, Element {
         return this;
     }
 
-    public XmlStringBuilder append(Collection<? extends Element> elements) {
+    public XmlStringBuilder append(Element element) {
-        return append(elements, effectiveXmlEnvironment);
+        return append(element.toXML(effectiveXmlEnvironment));
     }
 
-    public XmlStringBuilder append(Collection<? extends Element> elements, XmlEnvironment enclosingXmlEnvironment) {
+    public XmlStringBuilder append(Collection<? extends Element> elements) {
         for (Element element : elements) {
-            append(element.toXML(enclosingXmlEnvironment));
+            append(element);
         }
         return this;
     }

smack-core/src/test/java/org/jivesoftware/smack/StanzaCollectorTest.java

@@ -188,5 +188,10 @@ public class StanzaCollectorTest {
         public String toString() {
             return toXML().toString();
         }
+
+        @Override
+        public String getElementName() {
+            return "packetId";
+        }
     }
 }

smack-core/src/test/java/org/jivesoftware/smack/util/PacketParserUtilsTest.java

@@ -738,10 +738,6 @@ public class PacketParserUtilsTest {
             .a("type", "chat")
             .a("xml:lang", "en")
             .e("body")
-                // TODO: Remove the following xml:lang once Smack's serialization toXml() API is aware of a potential
-                // scoping xml:lang value. The out message stanza already declares an xml:lang with the exact same
-                // value, hence this statement is redundant.
-                .a("xml:lang", "en")
                 .t("This is a test of the emergency broadcast system, 1.")
             .up()
             .e("body")

smack-debug/src/main/java/org/jivesoftware/smackx/debugger/EnhancedDebugger.java

@@ -943,6 +943,11 @@ public class EnhancedDebugger extends SmackDebugger {
         public String toString() {
             return toXML((XmlEnvironment) null);
         }
+
+        @Override
+        public String getElementName() {
+            return null;
+        }
     }
 
     /**

smack-experimental/src/main/java/org/jivesoftware/smackx/hoxt/packet/AbstractHttpOverXmpp.java

@@ -16,6 +16,7 @@
  */
 package org.jivesoftware.smackx.hoxt.packet;
 
+import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.packet.IQ;
 import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.Objects;
@@ -145,12 +146,19 @@ public abstract class AbstractHttpOverXmpp extends IQ {
         protected abstract B getThis();
     }
 
+    private abstract static class HoxExtensionElement implements ExtensionElement {
+        @Override
+        public final String getNamespace() {
+            return NAMESPACE;
+        }
+    }
+
     /**
      * Representation of Data element.
      * <p>
      * This class is immutable.
      */
-    public static class Data implements NamedElement {
+    public static class Data extends HoxExtensionElement {
 
         public static final String ELEMENT = "data";
 
@@ -172,9 +180,9 @@ public abstract class AbstractHttpOverXmpp extends IQ {
          */
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.rightAngleBracket();
-            xml.element(child);
+            xml.append(child);
             xml.closeElement(this);
             return xml;
         }
@@ -199,7 +207,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
      * <p>
      * This class is immutable.
      */
-    public static class Text implements NamedElement {
+    public static class Text extends HoxExtensionElement {
 
         public static final String ELEMENT = "text";
 
@@ -216,7 +224,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.rightAngleBracket();
             xml.optAppend(text);
             xml.closeElement(this);
@@ -243,7 +251,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
      * <p>
      * This class is immutable.
      */
-    public static class Base64 implements NamedElement {
+    public static class Base64 extends HoxExtensionElement {
 
         public static final String ELEMENT = "base64";
 
@@ -260,7 +268,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.rightAngleBracket();
             xml.optAppend(text);
             xml.closeElement(this);
@@ -287,7 +295,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
      * <p>
      * This class is immutable.
      */
-    public static class Xml implements NamedElement {
+    public static class Xml extends HoxExtensionElement {
 
         public static final String ELEMENT = "xml";
 
@@ -304,7 +312,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.rightAngleBracket();
             xml.optAppend(text);
             xml.closeElement(this);
@@ -331,7 +339,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
      * <p>
      * This class is immutable.
      */
-    public static class ChunkedBase64 implements NamedElement {
+    public static class ChunkedBase64 extends HoxExtensionElement {
 
         public static final String ELEMENT = "chunkedBase64";
 
@@ -348,7 +356,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.attribute("streamId", streamId);
             xml.closeEmptyElement();
             return xml;
@@ -374,7 +382,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
      * <p>
      * This class is immutable.
      */
-    public static class Ibb implements NamedElement {
+    public static class Ibb extends HoxExtensionElement {
 
         public static final String ELEMENT = "ibb";
 
@@ -391,7 +399,7 @@ public abstract class AbstractHttpOverXmpp extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.attribute("sid", sid);
             xml.closeEmptyElement();
             return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/iot/control/element/SetData.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2016 Florian Schmaus
+ * Copyright © 2016-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,10 +18,10 @@ package org.jivesoftware.smackx.iot.control.element;
 
 import java.util.Locale;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
-public abstract class SetData implements NamedElement {
+public abstract class SetData implements ExtensionElement {
 
     public enum Type {
         BOOL,
@@ -76,6 +76,11 @@ public abstract class SetData implements NamedElement {
         return getType().toString();
     }
 
+    @Override
+    public final String getNamespace() {
+        return IoTSetRequest.NAMESPACE;
+    }
+
     /**
      * Returns the XML representation of this Element.
      *
@@ -83,7 +88,7 @@ public abstract class SetData implements NamedElement {
      */
     @Override
     public final XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         xml.attribute("name", name);
         xml.attribute("value", value);
         xml.closeEmptyElement();

smack-experimental/src/main/java/org/jivesoftware/smackx/iot/data/element/IoTDataExtensionElement.java

@@ -0,0 +1,28 @@
+/**
+ *
+ * Copyright 2019 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jivesoftware.smackx.iot.data.element;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+
+public abstract class IoTDataExtensionElement implements ExtensionElement {
+
+    @Override
+    public final String getNamespace() {
+        return IoTFieldsExtension.NAMESPACE;
+    }
+
+}

smack-experimental/src/main/java/org/jivesoftware/smackx/iot/data/element/IoTDataField.java

@@ -16,10 +16,9 @@
  */
 package org.jivesoftware.smackx.iot.data.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
-public abstract class IoTDataField implements NamedElement {
+public abstract class IoTDataField extends IoTDataExtensionElement {
 
     enum Type {
         integer("int"),
@@ -53,7 +52,7 @@ public abstract class IoTDataField implements NamedElement {
 
     @Override
     public final XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         xml.attribute("name", name).attribute("value", getValueString());
         // TODO handle 'unit' attribute as special case if <numeric/> is implemented.
         xml.closeEmptyElement();

smack-experimental/src/main/java/org/jivesoftware/smackx/iot/data/element/NodeElement.java

@@ -19,12 +19,10 @@ package org.jivesoftware.smackx.iot.data.element;
 import java.util.Collections;
 import java.util.List;
 
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
-
 import org.jivesoftware.smackx.iot.element.NodeInfo;
 
-public class NodeElement implements NamedElement {
+public class NodeElement extends IoTDataExtensionElement {
 
     public static final String ELEMENT = "node";
 
@@ -51,7 +49,7 @@ public class NodeElement implements NamedElement {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         nodeInfo.appendTo(xml);
         xml.rightAngleBracket();
 

smack-experimental/src/main/java/org/jivesoftware/smackx/iot/data/element/TimestampElement.java

@@ -20,10 +20,9 @@ import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
-public class TimestampElement implements NamedElement {
+public class TimestampElement extends IoTDataExtensionElement {
 
     public static final String ELEMENT = "timestamp";
 
@@ -46,7 +45,7 @@ public class TimestampElement implements NamedElement {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         xml.attribute("value", date);
         xml.rightAngleBracket();
 

smack-experimental/src/main/java/org/jivesoftware/smackx/jingle_filetransfer/element/Checksum.java

@@ -52,7 +52,7 @@ public class Checksum implements ExtensionElement {
         sb.optAttribute(ATTR_CREATOR, creator);
         sb.optAttribute(ATTR_NAME, name);
         sb.rightAngleBracket();
-        sb.element(file);
+        sb.append(file);
         sb.closeElement(this);
         return sb;
     }

smack-experimental/src/main/java/org/jivesoftware/smackx/jingle_filetransfer/element/JingleFileTransferChild.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Paul Schaub
+ * Copyright 2017 Paul Schaub, 2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.jivesoftware.smackx.jingle_filetransfer.element;
 import java.io.File;
 import java.util.Date;
 
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 import org.jivesoftware.smackx.hashes.element.HashElement;
@@ -27,8 +28,10 @@ import org.jivesoftware.smackx.jingle.element.JingleContentDescriptionChildEleme
 /**
  * Content of type File.
  */
-public class JingleFileTransferChild extends JingleContentDescriptionChildElement {
+public class JingleFileTransferChild implements JingleContentDescriptionChildElement {
     public static final String ELEMENT = "file";
+    public static final String NAMESPACE = JingleFileTransfer.NAMESPACE_V5;
+
     public static final String ELEM_DATE = "date";
     public static final String ELEM_DESC = "desc";
     public static final String ELEM_MEDIA_TYPE = "media-type";
@@ -87,8 +90,13 @@ public class JingleFileTransferChild extends JingleContentDescriptionChildElemen
     }
 
     @Override
-    public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder sb = new XmlStringBuilder(this);
+        return NAMESPACE;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingNamespace) {
+        XmlStringBuilder sb = new XmlStringBuilder(this, enclosingNamespace);
         sb.rightAngleBracket();
 
         sb.optElement(ELEM_DATE, date);

smack-experimental/src/main/java/org/jivesoftware/smackx/jingle_filetransfer/element/Range.java

@@ -16,7 +16,7 @@
  */
 package org.jivesoftware.smackx.jingle_filetransfer.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 import org.jivesoftware.smackx.hashes.element.HashElement;
@@ -24,9 +24,11 @@ import org.jivesoftware.smackx.hashes.element.HashElement;
 /**
  * RangeElement which specifies, which range of a file shall be transferred.
  */
-public class Range implements NamedElement {
+public class Range implements FullyQualifiedElement {
 
     public static final String ELEMENT = "range";
+    public static final String NAMESPACE = JingleFileTransferChild.NAMESPACE;
+
     public static final String ATTR_OFFSET = "offset";
     public static final String ATTR_LENGTH = "length";
 
@@ -99,6 +101,11 @@ public class Range implements NamedElement {
         return ELEMENT;
     }
 
+    @Override
+    public String getNamespace() {
+        return NAMESPACE;
+    }
+
     @Override
     public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
         XmlStringBuilder sb =  new XmlStringBuilder(this);
@@ -108,7 +115,7 @@ public class Range implements NamedElement {
 
         if (hash != null) {
             sb.rightAngleBracket();
-            sb.element(hash);
+            sb.append(hash);
             sb.closeElement(this);
         } else {
             sb.closeEmptyElement();

smack-experimental/src/main/java/org/jivesoftware/smackx/mam/element/MamElements.java

@@ -126,15 +126,14 @@ public class MamElements {
         }
 
         @Override
-        public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+        public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder();
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
-            xml.halfOpenElement(this);
+
-            xml.xmlnsAttribute(NAMESPACE);
             xml.optAttribute("queryid", getQueryId());
             xml.optAttribute("id", getId());
             xml.rightAngleBracket();
 
-            xml.element(getForwarded());
+            xml.append(getForwarded());
 
             xml.closeElement(this);
             return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/mam/element/MamFinIQ.java

@@ -124,7 +124,7 @@ public class MamFinIQ extends IQ {
             xml.setEmptyElement();
         } else {
             xml.rightAngleBracket();
-            xml.element(rsmSet);
+            xml.append(rsmSet);
         }
         return xml;
     }

smack-experimental/src/main/java/org/jivesoftware/smackx/mam/element/MamPrefsIQ.java

@@ -134,12 +134,12 @@ public class MamPrefsIQ extends IQ {
 
         if (alwaysJids != null) {
             MamElements.AlwaysJidListElement alwaysElement = new AlwaysJidListElement(alwaysJids);
-            xml.element(alwaysElement);
+            xml.append(alwaysElement);
         }
 
         if (neverJids != null) {
             MamElements.NeverJidListElement neverElement = new NeverJidListElement(neverJids);
-            xml.element(neverElement);
+            xml.append(neverElement);
         }
 
         return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/message_markup/element/BlockQuoteElement.java

@@ -16,14 +16,10 @@
  */
 package org.jivesoftware.smackx.message_markup.element;
 
-import org.jivesoftware.smack.util.XmlStringBuilder;
+public class BlockQuoteElement extends MarkupElement.BlockLevelMarkupElement {
-
-public class BlockQuoteElement implements MarkupElement.BlockLevelMarkupElement {
 
     public static final String ELEMENT = "bquote";
 
-    private final int start, end;
-
     /**
      * Create a new Block Quote element.
      *
@@ -31,18 +27,7 @@ public class BlockQuoteElement implements MarkupElement.BlockLevelMarkupElement
      * @param end end index
      */
     public BlockQuoteElement(int start, int end) {
-        this.start = start;
+        super(start, end);
-        this.end = end;
-    }
-
-    @Override
-    public int getStart() {
-        return start;
-    }
-
-    @Override
-    public int getEnd() {
-        return end;
     }
 
     @Override
@@ -50,13 +35,4 @@ public class BlockQuoteElement implements MarkupElement.BlockLevelMarkupElement
         return ELEMENT;
     }
 
-    @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder();
-        xml.halfOpenElement(this);
-        xml.attribute(ATTR_START, getStart());
-        xml.attribute(ATTR_END, getEnd());
-        xml.closeEmptyElement();
-        return xml;
-    }
 }

smack-experimental/src/main/java/org/jivesoftware/smackx/message_markup/element/CodeBlockElement.java

@@ -16,14 +16,10 @@
  */
 package org.jivesoftware.smackx.message_markup.element;
 
-import org.jivesoftware.smack.util.XmlStringBuilder;
+public class CodeBlockElement extends MarkupElement.BlockLevelMarkupElement {
-
-public class CodeBlockElement implements MarkupElement.BlockLevelMarkupElement {
 
     public static final String ELEMENT = "bcode";
 
-    private final int start, end;
-
     /**
      * Create a new Code Block element.
      *
@@ -31,18 +27,7 @@ public class CodeBlockElement implements MarkupElement.BlockLevelMarkupElement {
      * @param end end index
      */
     public CodeBlockElement(int start, int end) {
-        this.start = start;
+        super(start, end);
-        this.end = end;
-    }
-
-    @Override
-    public int getStart() {
-        return start;
-    }
-
-    @Override
-    public int getEnd() {
-        return end;
     }
 
     @Override
@@ -50,13 +35,4 @@ public class CodeBlockElement implements MarkupElement.BlockLevelMarkupElement {
         return ELEMENT;
     }
 
-    @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder();
-        xml.halfOpenElement(this);
-        xml.attribute(ATTR_START, getStart());
-        xml.attribute(ATTR_END, getEnd());
-        xml.closeEmptyElement();
-        return xml;
-    }
 }

smack-experimental/src/main/java/org/jivesoftware/smackx/message_markup/element/ListElement.java

@@ -19,15 +19,14 @@ package org.jivesoftware.smackx.message_markup.element;
 import java.util.Collections;
 import java.util.List;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
-public class ListElement implements MarkupElement.MarkupChildElement {
+public class ListElement extends MarkupElement.NonEmptyChildElement {
 
     public static final String ELEMENT = "list";
     public static final String ELEM_LI = "li";
 
-    private final int start, end;
     private final List<ListEntryElement> entries;
 
     /**
@@ -38,21 +37,10 @@ public class ListElement implements MarkupElement.MarkupChildElement {
      * @param entries list entries
      */
     public ListElement(int start, int end, List<ListEntryElement> entries) {
-        this.start = start;
+        super(start, end);
-        this.end = end;
         this.entries = Collections.unmodifiableList(entries);
     }
 
-    @Override
-    public int getStart() {
-        return start;
-    }
-
-    @Override
-    public int getEnd() {
-        return end;
-    }
-
     /**
      * Return a list of all list entries.
      *
@@ -68,22 +56,11 @@ public class ListElement implements MarkupElement.MarkupChildElement {
     }
 
     @Override
-    public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public void appendInnerXml(XmlStringBuilder xml) {
-        XmlStringBuilder xml = new XmlStringBuilder();
+        xml.append(getEntries());
-        xml.halfOpenElement(this);
-        xml.attribute(ATTR_START, getStart());
-        xml.attribute(ATTR_END, getEnd());
-        xml.rightAngleBracket();
-
-        for (ListEntryElement li : getEntries()) {
-            xml.append(li.toXML());
-        }
-
-        xml.closeElement(this);
-        return xml;
     }
 
-    public static class ListEntryElement implements NamedElement {
+    public static class ListEntryElement implements ExtensionElement {
 
         private final int start;
 
@@ -109,11 +86,15 @@ public class ListElement implements MarkupElement.MarkupChildElement {
             return ELEM_LI;
         }
 
+        @Override
+        public String getNamespace() {
+            return MarkupElement.NAMESPACE;
+        }
+
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder();
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
-            xml.halfOpenElement(this);
+            xml.attribute(MarkupElement.MarkupChildElement.ATTR_START, getStart());
-            xml.attribute(ATTR_START, getStart());
             xml.closeEmptyElement();
             return xml;
         }

smack-experimental/src/main/java/org/jivesoftware/smackx/message_markup/element/MarkupElement.java

@@ -22,7 +22,6 @@ import java.util.List;
 import java.util.Set;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 public class MarkupElement implements ExtensionElement {
@@ -267,46 +266,89 @@ public class MarkupElement implements ExtensionElement {
         }
     }
 
-
-
-
-
-
-
-
-
-
-
-
-
-
     /**
      * Interface for child elements.
      */
-    public interface MarkupChildElement extends NamedElement {
+    public abstract static class MarkupChildElement implements ExtensionElement {
 
-        String ATTR_START = "start";
+        public static final String ATTR_START = "start";
-        String ATTR_END = "end";
+        public static final String ATTR_END = "end";
+
+        private final int start, end;
+
+        protected MarkupChildElement(int start, int end) {
+            this.start = start;
+            this.end = end;
+        }
 
         /**
          * Return the start index of this element.
          *
          * @return start index
          */
-        int getStart();
+        public final int getStart() {
+            return start;
+        }
 
         /**
          * Return the end index of this element.
          *
          * @return end index
          */
-        int getEnd();
+        public final int getEnd() {
+            return end;
+        }
+
+        @Override
+        public final String getNamespace() {
+            return NAMESPACE;
+        }
+
+        @Override
+        public final XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
+            xml.attribute(ATTR_START, getStart());
+            xml.attribute(ATTR_END, getEnd());
+
+            afterXmlPrelude(xml);
+            return xml;
+        }
+
+        protected abstract void afterXmlPrelude(XmlStringBuilder xml);
+    }
+
+    public abstract static class NonEmptyChildElement extends MarkupChildElement {
+
+        protected NonEmptyChildElement(int start, int end) {
+            super(start, end);
+        }
+
+        @Override
+        protected final void afterXmlPrelude(XmlStringBuilder xml) {
+            xml.rightAngleBracket();
+
+            appendInnerXml(xml);
+
+            xml.closeElement(this);
+        }
+
+        protected abstract void appendInnerXml(XmlStringBuilder xml);
+
     }
 
     /**
      * Interface for block level child elements.
      */
-    public interface BlockLevelMarkupElement extends MarkupChildElement {
+    public abstract static class BlockLevelMarkupElement extends MarkupChildElement {
+
+        protected BlockLevelMarkupElement(int start, int end) {
+            super(start, end);
+        }
+
+        @Override
+        protected final void afterXmlPrelude(XmlStringBuilder xml) {
+            xml.closeEmptyElement();
+        }
 
     }
 }

smack-experimental/src/main/java/org/jivesoftware/smackx/message_markup/element/SpanElement.java

@@ -21,11 +21,10 @@ import java.util.Set;
 
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
-public class SpanElement implements MarkupElement.MarkupChildElement {
+public class SpanElement extends MarkupElement.NonEmptyChildElement {
 
     public static final String ELEMENT = "span";
 
-    private final int start, end;
     private final Set<SpanStyle> styles;
 
     /**
@@ -36,21 +35,10 @@ public class SpanElement implements MarkupElement.MarkupChildElement {
      * @param styles list of styles that apply to this span
      */
     public SpanElement(int start, int end, Set<SpanStyle> styles) {
-        this.start = start;
+        super(start, end);
-        this.end = end;
         this.styles = Collections.unmodifiableSet(styles);
     }
 
-    @Override
-    public int getStart() {
-        return start;
-    }
-
-    @Override
-    public int getEnd() {
-        return end;
-    }
-
     /**
      * Return all styles of this span.
      *
@@ -76,18 +64,9 @@ public class SpanElement implements MarkupElement.MarkupChildElement {
     }
 
     @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    protected void appendInnerXml(XmlStringBuilder xml) {
-        XmlStringBuilder xml = new XmlStringBuilder();
-        xml.halfOpenElement(this);
-        xml.attribute(ATTR_START, getStart());
-        xml.attribute(ATTR_END, getEnd());
-        xml.rightAngleBracket();
-
         for (SpanStyle style : getStyles()) {
-            xml.halfOpenElement(style.toString()).closeEmptyElement();
+            xml.emptyElement(style);
         }
-
-        xml.closeElement(this);
-        return xml;
     }
 }

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightAffiliationsIQ.java

@@ -62,7 +62,7 @@ public class MUCLightAffiliationsIQ extends IQ {
         Iterator<Map.Entry<Jid, MUCLightAffiliation>> it = affiliations.entrySet().iterator();
         while (it.hasNext()) {
             Map.Entry<Jid, MUCLightAffiliation> pair = it.next();
-            xml.element(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
+            xml.append(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
         }
 
         return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightBlockingIQ.java

@@ -90,7 +90,7 @@ public class MUCLightBlockingIQ extends IQ {
         Iterator<Map.Entry<Jid, Boolean>> it = map.entrySet().iterator();
         while (it.hasNext()) {
             Map.Entry<Jid, Boolean> pair = it.next();
-            xml.element(new BlockingElement(pair.getKey(), pair.getValue(), isRoom));
+            xml.append(new BlockingElement(pair.getKey(), pair.getValue(), isRoom));
         }
     }
 

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightChangeAffiliationsIQ.java

@@ -71,7 +71,7 @@ public class MUCLightChangeAffiliationsIQ extends IQ {
             Iterator<Map.Entry<Jid, MUCLightAffiliation>> it = affiliations.entrySet().iterator();
             while (it.hasNext()) {
                 Map.Entry<Jid, MUCLightAffiliation> pair = it.next();
-                xml.element(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
+                xml.append(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
             }
         }
 

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightConfigurationIQ.java

@@ -52,7 +52,7 @@ public class MUCLightConfigurationIQ extends IQ {
     protected IQChildElementXmlStringBuilder getIQChildElementBuilder(IQChildElementXmlStringBuilder xml) {
         xml.rightAngleBracket();
         xml.optElement("version", version);
-        xml.element(new ConfigurationElement(configuration));
+        xml.append(new ConfigurationElement(configuration));
         return xml;
     }
 

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightCreateIQ.java

@@ -99,10 +99,10 @@ public class MUCLightCreateIQ extends IQ {
     @Override
     protected IQChildElementXmlStringBuilder getIQChildElementBuilder(IQChildElementXmlStringBuilder xml) {
         xml.rightAngleBracket();
-        xml.element(new ConfigurationElement(configuration));
+        xml.append(new ConfigurationElement(configuration));
 
         if (!occupants.isEmpty()) {
-            xml.element(new OccupantsElement(occupants));
+            xml.append(new OccupantsElement(occupants));
         }
 
         return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightElements.java

@@ -104,7 +104,7 @@ public abstract class MUCLightElements {
             Iterator<Map.Entry<Jid, MUCLightAffiliation>> it = affiliations.entrySet().iterator();
             while (it.hasNext()) {
                 Map.Entry<Jid, MUCLightAffiliation> pair = it.next();
-                xml.element(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
+                xml.append(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
             }
 
             xml.closeElement(this);
@@ -303,7 +303,7 @@ public abstract class MUCLightElements {
             Iterator<Map.Entry<Jid, MUCLightAffiliation>> it = occupants.entrySet().iterator();
             while (it.hasNext()) {
                 Map.Entry<Jid, MUCLightAffiliation> pair = it.next();
-                xml.element(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
+                xml.append(new UserWithAffiliationElement(pair.getKey(), pair.getValue()));
             }
 
             xml.closeElement("occupants");

smack-experimental/src/main/java/org/jivesoftware/smackx/muclight/element/MUCLightInfoIQ.java

@@ -62,8 +62,8 @@ public class MUCLightInfoIQ extends IQ {
     protected IQChildElementXmlStringBuilder getIQChildElementBuilder(IQChildElementXmlStringBuilder xml) {
         xml.rightAngleBracket();
         xml.optElement("version", version);
-        xml.element(new ConfigurationElement(configuration));
+        xml.append(new ConfigurationElement(configuration));
-        xml.element(new OccupantsElement(occupants));
+        xml.append(new OccupantsElement(occupants));
         return xml;
     }
 

smack-experimental/src/main/java/org/jivesoftware/smackx/push_notifications/element/EnablePushNotificationsIQ.java

@@ -115,7 +115,7 @@ public class EnablePushNotificationsIQ extends IQ {
                 dataForm.addField(field.build());
             }
 
-            xml.element(dataForm);
+            xml.append(dataForm);
         }
 
         return xml;

smack-experimental/src/main/java/org/jivesoftware/smackx/spoiler/element/SpoilerElement.java

@@ -131,12 +131,7 @@ public class SpoilerElement implements ExtensionElement {
         return map;
     }
 
-    /**
+    @Override
-     * Return the language of the hint.
-     * May be null.
-     *
-     * @return language of hint text
-     */
     public String getLanguage() {
         return language;
     }
@@ -153,8 +148,7 @@ public class SpoilerElement implements ExtensionElement {
 
     @Override
     public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
-        xml.optXmlLangAttribute(getLanguage());
         if (getHint() == null) {
             xml.closeEmptyElement();
         } else {

smack-extensions/src/main/java/org/jivesoftware/smackx/address/MultipleRecipientManager.java

@@ -212,19 +212,19 @@ public class MultipleRecipientManager {
         if (to != null) {
             for (Jid jid : to) {
                 packet.setTo(jid);
-                connection.sendStanza(new PacketCopy(packet.toXML()));
+                connection.sendStanza(new PacketCopy(packet));
             }
         }
         if (cc != null) {
             for (Jid jid : cc) {
                 packet.setTo(jid);
-                connection.sendStanza(new PacketCopy(packet.toXML()));
+                connection.sendStanza(new PacketCopy(packet));
             }
         }
         if (bcc != null) {
             for (Jid jid : bcc) {
                 packet.setTo(jid);
-                connection.sendStanza(new PacketCopy(packet.toXML()));
+                connection.sendStanza(new PacketCopy(packet));
             }
         }
     }
@@ -297,6 +297,7 @@ public class MultipleRecipientManager {
      */
     private static final class PacketCopy extends Stanza {
 
+        private final String elementName;
         private final CharSequence text;
 
         /**
@@ -305,8 +306,9 @@ public class MultipleRecipientManager {
          *
          * @param text the whole text of the stanza to send
          */
-        private PacketCopy(CharSequence text) {
+        private PacketCopy(Stanza stanza) {
-            this.text = text;
+            this.elementName = stanza.getElementName();
+            this.text = stanza.toXML();
         }
 
         @Override
@@ -319,6 +321,11 @@ public class MultipleRecipientManager {
             return toXML().toString();
         }
 
+        @Override
+        public String getElementName() {
+            return elementName;
+        }
+
     }
 
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/address/packet/MultipleAddresses.java

@@ -21,7 +21,6 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 import org.jxmpp.jid.Jid;
@@ -129,7 +128,7 @@ public class MultipleAddresses implements ExtensionElement {
         return buf;
     }
 
-    public static final class Address implements NamedElement {
+    public static final class Address implements ExtensionElement {
 
         public static final String ELEMENT = "address";
 
@@ -193,10 +192,15 @@ public class MultipleAddresses implements ExtensionElement {
             return ELEMENT;
         }
 
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
+
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder buf = new XmlStringBuilder();
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
-            buf.halfOpenElement(this).attribute("type", type);
+            buf.attribute("type", type);
             buf.optAttribute("jid", jid);
             buf.optAttribute("node", node);
             buf.optAttribute("desc", description);
@@ -209,5 +213,6 @@ public class MultipleAddresses implements ExtensionElement {
             buf.closeEmptyElement();
             return buf;
         }
+
     }
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/bytestreams/socks5/packet/Bytestream.java

@@ -21,8 +21,8 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.packet.IQ;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.InternetAddress;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.XmlStringBuilder;
@@ -260,13 +260,20 @@ public class Bytestream extends IQ {
         return xml;
     }
 
+    private abstract static class BytestreamExtensionElement implements ExtensionElement {
+        @Override
+        public final String getNamespace() {
+            return NAMESPACE;
+        }
+    }
+
     /**
      * Stanza extension that represents a potential SOCKS5 proxy for the file transfer. Stream hosts
      * are forwarded to the target of the file transfer who then chooses and connects to one.
      *
      * @author Alexander Wenckus
      */
-    public static class StreamHost implements NamedElement {
+    public static class StreamHost extends BytestreamExtensionElement {
 
         public static String ELEMENTNAME = "streamhost";
 
@@ -342,7 +349,7 @@ public class Bytestream extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.attribute("jid", getJID());
             xml.attribute("host", address);
             if (getPort() != 0) {
@@ -366,7 +373,7 @@ public class Bytestream extends IQ {
      *
      * @author Alexander Wenckus
      */
-    public static class StreamHostUsed implements NamedElement {
+    public static class StreamHostUsed extends BytestreamExtensionElement {
 
         public static String ELEMENTNAME = "streamhost-used";
 
@@ -397,7 +404,7 @@ public class Bytestream extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.attribute("jid", getJID());
             xml.closeEmptyElement();
             return xml;
@@ -409,7 +416,7 @@ public class Bytestream extends IQ {
      *
      * @author Alexander Wenckus
      */
-    public static class Activate implements NamedElement {
+    public static class Activate extends BytestreamExtensionElement {
 
         public static String ELEMENTNAME = "activate";
 
@@ -440,12 +447,13 @@ public class Bytestream extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.rightAngleBracket();
             xml.escape(getTarget());
             xml.closeElement(this);
             return xml;
         }
+
     }
 
     /**

smack-extensions/src/main/java/org/jivesoftware/smackx/delay/packet/DelayInformation.java

@@ -103,7 +103,7 @@ public class DelayInformation implements ExtensionElement {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         xml.attribute("stamp", XmppDateTime.formatXEP0082Date(stamp));
         xml.optAttribute("from", from);
         xml.rightAngleBracket();

smack-extensions/src/main/java/org/jivesoftware/smackx/forward/packet/Forwarded.java

@@ -72,10 +72,10 @@ public class Forwarded implements ExtensionElement {
 
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
         xml.rightAngleBracket();
         xml.optElement(getDelayInformation());
-        xml.append(forwardedPacket.toXML(NAMESPACE));
+        xml.append(forwardedPacket);
         xml.closeElement(this);
         return xml;
     }

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleContent.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Florian Schmaus
+ * Copyright 2017-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,8 @@
  */
 package org.jivesoftware.smackx.jingle.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.XmlStringBuilder;
@@ -24,9 +25,10 @@ import org.jivesoftware.smack.util.XmlStringBuilder;
 /**
  * Jingle content element.
  */
-public final class JingleContent implements NamedElement {
+public final class JingleContent implements FullyQualifiedElement {
 
     public static final String ELEMENT = "content";
+    public static final String NAMESPACE = Jingle.NAMESPACE;
 
     public static final String CREATOR_ATTRIBUTE_NAME = "creator";
 
@@ -132,8 +134,13 @@ public final class JingleContent implements NamedElement {
     }
 
     @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        return NAMESPACE;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingXmlEnvironment);
         xml.attribute(CREATOR_ATTRIBUTE_NAME, creator);
         xml.optAttribute(DISPOSITION_ATTRIBUTE_NAME, disposition);
         xml.attribute(NAME_ATTRIBUTE_NAME, name);

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleContentDescriptionChildElement.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright © 2014-2017 Florian Schmaus
+ * Copyright © 2014-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,18 +16,12 @@
  */
 package org.jivesoftware.smackx.jingle.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
 
 /**
  * An element found usually in 'description' elements.
  *
  */
-public abstract class JingleContentDescriptionChildElement implements NamedElement {
+public interface JingleContentDescriptionChildElement extends FullyQualifiedElement {
 
-    public static final String ELEMENT = "payload-type";
-
-    @Override
-    public String getElementName() {
-        return ELEMENT;
-    }
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleContentTransport.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Florian Schmaus
+ * Copyright 2017-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,7 @@ import java.util.Collections;
 import java.util.List;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 /**
@@ -66,8 +67,8 @@ public abstract class JingleContentTransport implements ExtensionElement {
     }
 
     @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, xmlEnvironment);
         addExtraAttributes(xml);
 
         if (candidates.isEmpty() && info == null) {

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleContentTransportCandidate.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Florian Schmaus
+ * Copyright 2017-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,13 +16,13 @@
  */
 package org.jivesoftware.smackx.jingle.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
 
 /**
  * An element found usually in Jingle 'transport' elements.
  *
  */
-public abstract class JingleContentTransportCandidate implements NamedElement {
+public abstract class JingleContentTransportCandidate implements FullyQualifiedElement {
 
     public static final String ELEMENT = "candidate";
 

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleContentTransportInfo.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Paul Schaub
+ * Copyright 2017 Paul Schaub, 2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,11 +16,11 @@
  */
 package org.jivesoftware.smackx.jingle.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
 
 /**
  * Abstract JingleContentTransportInfo element.
  */
-public abstract class JingleContentTransportInfo implements NamedElement {
+public interface JingleContentTransportInfo extends FullyQualifiedElement {
 
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/element/JingleReason.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Florian Schmaus
+ * Copyright 2017-2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,8 @@ package org.jivesoftware.smackx.jingle.element;
 import java.util.HashMap;
 import java.util.Map;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -29,9 +30,10 @@ import org.jivesoftware.smack.util.XmlStringBuilder;
  * @see <a href="https://xmpp.org/extensions/xep-0166.html#def-reason">XEP-0166 § 7.4</a>
  *
  */
-public class JingleReason implements NamedElement {
+public class JingleReason implements FullyQualifiedElement {
 
     public static final String ELEMENT = "reason";
+    public static final String NAMESPACE = Jingle.NAMESPACE;
 
     public static AlternativeSession AlternativeSession(String sessionId) {
         return new AlternativeSession(sessionId);
@@ -114,11 +116,16 @@ public class JingleReason implements NamedElement {
     }
 
     @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        return NAMESPACE;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingXmlEnvironment);
         xml.rightAngleBracket();
 
-        xml.emptyElement(reason.asString);
+        xml.emptyElement(reason);
 
         xml.closeElement(this);
         return xml;

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/transports/jingle_s5b/elements/JingleS5BTransportCandidate.java

@@ -16,6 +16,7 @@
  */
 package org.jivesoftware.smackx.jingle.transports.jingle_s5b.elements;
 
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.InternetAddress;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.StringUtils;
@@ -33,6 +34,8 @@ import org.jxmpp.stringprep.XmppStringprepException;
  */
 public final class JingleS5BTransportCandidate extends JingleContentTransportCandidate {
 
+    public static final String NAMESPACE = JingleS5BTransport.NAMESPACE_V1;
+
     public static final String ATTR_CID = "cid";
     public static final String ATTR_HOST = "host";
     public static final String ATTR_JID = "jid";
@@ -130,10 +133,15 @@ public final class JingleS5BTransportCandidate extends JingleContentTransportCan
         return new Bytestream.StreamHost(jid, host, port);
     }
 
+
     @Override
-    public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder xml = new XmlStringBuilder();
+        return NAMESPACE;
-        xml.halfOpenElement(this);
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
+        XmlStringBuilder xml = new XmlStringBuilder(this, enclosingXmlEnvironment);
         xml.attribute(ATTR_CID, cid);
         xml.attribute(ATTR_HOST, host);
         xml.attribute(ATTR_JID, jid);
@@ -207,4 +215,5 @@ public final class JingleS5BTransportCandidate extends JingleContentTransportCan
             return new JingleS5BTransportCandidate(cid, host, jid, port, priority, type);
         }
     }
+
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/transports/jingle_s5b/elements/JingleS5BTransportInfo.java

@@ -16,6 +16,7 @@
  */
 package org.jivesoftware.smackx.jingle.transports.jingle_s5b.elements;
 
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 import org.jivesoftware.smackx.jingle.element.JingleContentTransportInfo;
@@ -23,7 +24,14 @@ import org.jivesoftware.smackx.jingle.element.JingleContentTransportInfo;
 /**
  * Class representing possible SOCKS5 TransportInfo elements.
  */
-public abstract class JingleS5BTransportInfo extends JingleContentTransportInfo {
+public abstract class JingleS5BTransportInfo implements JingleContentTransportInfo {
+
+    public static final String NAMESPACE = JingleS5BTransport.NAMESPACE_V1;
+
+    @Override
+    public final String getNamespace() {
+        return NAMESPACE;
+    }
 
     public abstract static class JingleS5BCandidateTransportInfo extends JingleS5BTransportInfo {
         public static final String ATTR_CID = "cid";
@@ -39,9 +47,8 @@ public abstract class JingleS5BTransportInfo extends JingleContentTransportInfo
         }
 
         @Override
-        public final XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+        public final XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
-            XmlStringBuilder xml = new XmlStringBuilder();
+            XmlStringBuilder xml = new XmlStringBuilder(this, xmlEnvironment);
-            xml.halfOpenElement(this);
             xml.attribute(ATTR_CID, getCandidateId());
             xml.closeEmptyElement();
             return xml;

smack-extensions/src/main/java/org/jivesoftware/smackx/mood/element/MoodElement.java

@@ -17,8 +17,10 @@
 package org.jivesoftware.smackx.mood.element;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
 import org.jivesoftware.smack.packet.Message;
 import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -107,8 +109,8 @@ public class MoodElement implements ExtensionElement {
     }
 
     @Override
-    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
-        XmlStringBuilder xml = new XmlStringBuilder(this);
+        XmlStringBuilder xml = new XmlStringBuilder(this, xmlEnvironment);
 
         if (mood == null && text == null) {
             // Empty mood element used as STOP signal
@@ -152,7 +154,7 @@ public class MoodElement implements ExtensionElement {
      * {@link NamedElement} which represents the mood.
      * This element has the element name of the mood selected from {@link Mood}.
      */
-    public static class MoodSubjectElement implements NamedElement {
+    public static class MoodSubjectElement implements FullyQualifiedElement {
 
         private final Mood mood;
         private final MoodConcretisation concretisation;
@@ -168,16 +170,17 @@ public class MoodElement implements ExtensionElement {
         }
 
         @Override
-        public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+        public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
-            XmlStringBuilder xml = new XmlStringBuilder();
+            XmlStringBuilder xml = new XmlStringBuilder(this, xmlEnvironment);
 
             if (concretisation == null) {
-                return xml.emptyElement(getElementName());
+                return xml.closeEmptyElement();
             }
 
-            return xml.openElement(getElementName())
+            xml.rightAngleBracket()
-                    .append(concretisation.toXML())
+                .append(concretisation)
-                    .closeElement(getElementName());
+                .closeElement(this);
+            return xml;
         }
 
         /**
@@ -197,5 +200,10 @@ public class MoodElement implements ExtensionElement {
         public MoodConcretisation getConcretisation() {
             return concretisation;
         }
+
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
     }
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/muc/packet/MUCUser.java

@@ -323,7 +323,7 @@ public class MUCUser implements ExtensionElement {
      *
      * @author Gaston Dombiak
      */
-    public static class Decline implements NamedElement {
+    public static class Decline implements ExtensionElement {
         public static final String ELEMENT = "decline";
 
         private final String reason;
@@ -370,7 +370,7 @@ public class MUCUser implements ExtensionElement {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.optAttribute("to", getTo());
             xml.optAttribute("from", getFrom());
             xml.rightAngleBracket();
@@ -383,6 +383,11 @@ public class MUCUser implements ExtensionElement {
         public String getElementName() {
             return ELEMENT;
         }
+
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
     }
 
     /**

smack-extensions/src/main/java/org/jivesoftware/smackx/xdata/FormField.java

@@ -417,7 +417,7 @@ public final class FormField implements FullyQualifiedElement {
         } else {
             buf.rightAngleBracket();
 
-            buf.append(formFieldChildElements, enclosingNamespace);
+            buf.append(formFieldChildElements);
 
             buf.closeElement(this);
         }

smack-extensions/src/main/java/org/jivesoftware/smackx/xdata/packet/DataForm.java

@@ -325,15 +325,10 @@ public class DataForm implements ExtensionElement {
 
     @Override
     public XmlStringBuilder toXML(XmlEnvironment xmlEnvironment) {
-        XmlStringBuilder buf = new XmlStringBuilder(this);
+        XmlStringBuilder buf = new XmlStringBuilder(this, xmlEnvironment);
         buf.attribute("type", getType());
         buf.rightAngleBracket();
 
-        XmlEnvironment dataFormxmlEnvironment = XmlEnvironment.builder()
-                        .withNamespace(NAMESPACE)
-                        .withNext(xmlEnvironment)
-                        .build();
-
         buf.optElement("title", getTitle());
         for (String instruction : getInstructions()) {
             buf.element("instructions", instruction);
@@ -347,7 +342,7 @@ public class DataForm implements ExtensionElement {
             buf.append(item.toXML());
         }
         // Add all form fields.
-        buf.append(getFields(), dataFormxmlEnvironment);
+        buf.append(getFields());
         for (Element element : extensionElements) {
             buf.append(element.toXML());
         }

smack-extensions/src/main/java/org/jivesoftware/smackx/xdatalayout/packet/DataLayout.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2014 Anno van Vliet
+ * Copyright 2014 Anno van Vliet, 2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,6 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
 /**
@@ -96,24 +95,14 @@ public class DataLayout implements ExtensionElement {
         buf.optAttribute("label", getLabel());
         buf.rightAngleBracket();
 
-        walkList(buf, getPageLayout());
+        buf.append(getPageLayout());
 
         buf.closeElement(this);
 
         return buf;
     }
 
-    /**
+    public static class Fieldref extends DataFormLayoutElement{
-     * @param buf TODO javadoc me please
-     * @param pageLayout TODO javadoc me please
-     */
-    private static void walkList(XmlStringBuilder buf, List<DataFormLayoutElement> pageLayout) {
-        for (DataFormLayoutElement object : pageLayout) {
-            buf.append(object.toXML());
-        }
-    }
-
-    public static class Fieldref implements DataFormLayoutElement{
 
         public static final String ELEMENT = "fieldref";
         private final String var;
@@ -128,7 +117,7 @@ public class DataLayout implements ExtensionElement {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder buf = new XmlStringBuilder(this);
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
             buf.attribute("var", getVar());
             buf.closeEmptyElement();
             return buf;
@@ -150,7 +139,7 @@ public class DataLayout implements ExtensionElement {
 
     }
 
-    public static class Section implements DataFormLayoutElement{
+    public static class Section extends DataFormLayoutElement{
 
         public static final String ELEMENT = "section";
         private final List<DataFormLayoutElement> sectionLayout = new ArrayList<>();
@@ -188,11 +177,12 @@ public class DataLayout implements ExtensionElement {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder buf = new XmlStringBuilder(this);
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
             buf.optAttribute("label", getLabel());
             buf.rightAngleBracket();
 
-            walkList(buf, getSectionLayout());
+            buf.append(getSectionLayout());
+
             buf.closeElement(ELEMENT);
             return buf;
         }
@@ -213,13 +203,13 @@ public class DataLayout implements ExtensionElement {
 
     }
 
-    public static class Reportedref implements DataFormLayoutElement{
+    public static class Reportedref extends DataFormLayoutElement{
 
         public static final String ELEMENT = "reportedref";
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder buf = new XmlStringBuilder(this);
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
             buf.closeEmptyElement();
             return buf;
         }
@@ -231,7 +221,7 @@ public class DataLayout implements ExtensionElement {
 
     }
 
-    public static class Text implements DataFormLayoutElement{
+    public static class Text extends DataFormLayoutElement{
         public static final String ELEMENT = "text";
         private final String text;
 
@@ -245,8 +235,10 @@ public class DataLayout implements ExtensionElement {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder buf = new XmlStringBuilder();
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
-            buf.element(ELEMENT, getText());
+            buf.rightAngleBracket();
+            buf.escape(getText());
+            buf.closeElement(this);
             return buf;
         }
 
@@ -266,7 +258,11 @@ public class DataLayout implements ExtensionElement {
 
     }
 
-    public interface DataFormLayoutElement extends NamedElement {
+    public abstract static class DataFormLayoutElement implements ExtensionElement {
+        @Override
+        public final String getNamespace() {
+            return NAMESPACE;
+        }
     }
 
 }

smack-extensions/src/main/java/org/jivesoftware/smackx/xdatavalidation/packet/ValidateElement.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2014 Anno van Vliet
+ * Copyright 2014 Anno van Vliet, 2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,8 @@ package org.jivesoftware.smackx.xdatavalidation.packet;
 import javax.xml.namespace.QName;
 
 import org.jivesoftware.smack.datatypes.UInt32;
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -336,7 +337,7 @@ public abstract class ValidateElement implements FormFieldChildElement {
      * This element indicates for "list-multi", that a minimum and maximum number of options should be selected and/or
      * entered.
      */
-    public static class ListRange implements NamedElement {
+    public static class ListRange implements FullyQualifiedElement {
 
         public static final String ELEMENT = "list-range";
         private final UInt32 min;
@@ -363,8 +364,8 @@ public abstract class ValidateElement implements FormFieldChildElement {
         }
 
         @Override
-        public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+        public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
-            XmlStringBuilder buf = new XmlStringBuilder(this);
+            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingXmlEnvironment);
             buf.optAttribute("min", getMin());
             buf.optAttribute("max", getMax());
             buf.closeEmptyElement();
@@ -394,6 +395,11 @@ public abstract class ValidateElement implements FormFieldChildElement {
             return max;
         }
 
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
+
     }
 
     /**

smack-extensions/src/test/java/org/jivesoftware/smackx/jingle/JingleContentTest.java

@@ -70,7 +70,7 @@ public class JingleContentTest extends SmackTestSuite {
         assertEquals(content1.toXML().toString(), builder.build().toXML().toString());
 
         String xml =
-                "<content creator='initiator' disposition='session' name='A name' senders='both'>" +
+                "<content xmlns='urn:xmpp:jingle:1' creator='initiator' disposition='session' name='A name' senders='both'>" +
                 "</content>";
         assertEquals(xml, content1.toXML().toString());
     }

smack-extensions/src/test/java/org/jivesoftware/smackx/jingle/JingleReasonTest.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2017 Paul Schaub
+ * Copyright 2017-2019 Paul Schaub, 2019 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,13 +16,14 @@
  */
 package org.jivesoftware.smackx.jingle;
 
-import static junit.framework.TestCase.assertEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.jivesoftware.smack.test.util.SmackTestSuite;
 
 import org.jivesoftware.smackx.jingle.element.JingleReason;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 /**
  * Test JingleReason functionality.
@@ -31,56 +32,67 @@ public class JingleReasonTest extends SmackTestSuite {
 
     @Test
     public void parserTest() {
-        assertEquals("<reason><success/></reason>",
+        assertReasonXml("<reason><success/></reason>",
-                JingleReason.Success.toXML().toString());
+                JingleReason.Success);
-        assertEquals("<reason><busy/></reason>",
+        assertReasonXml("<reason><busy/></reason>",
-                JingleReason.Busy.toXML().toString());
+                JingleReason.Busy);
-        assertEquals("<reason><cancel/></reason>",
+        assertReasonXml("<reason><cancel/></reason>",
-                JingleReason.Cancel.toXML().toString());
+                JingleReason.Cancel);
-        assertEquals("<reason><connectivity-error/></reason>",
+        assertReasonXml("<reason><connectivity-error/></reason>",
-                JingleReason.ConnectivityError.toXML().toString());
+                JingleReason.ConnectivityError);
-        assertEquals("<reason><decline/></reason>",
+        assertReasonXml("<reason><decline/></reason>",
-                JingleReason.Decline.toXML().toString());
+                JingleReason.Decline);
-        assertEquals("<reason><expired/></reason>",
+        assertReasonXml("<reason><expired/></reason>",
-                JingleReason.Expired.toXML().toString());
+                JingleReason.Expired);
-        assertEquals("<reason><unsupported-transports/></reason>",
+        assertReasonXml("<reason><unsupported-transports/></reason>",
-                JingleReason.UnsupportedTransports.toXML().toString());
+                JingleReason.UnsupportedTransports);
-        assertEquals("<reason><failed-transport/></reason>",
+        assertReasonXml("<reason><failed-transport/></reason>",
-                JingleReason.FailedTransport.toXML().toString());
+                JingleReason.FailedTransport);
-        assertEquals("<reason><general-error/></reason>",
+        assertReasonXml("<reason><general-error/></reason>",
-                JingleReason.GeneralError.toXML().toString());
+                JingleReason.GeneralError);
-        assertEquals("<reason><gone/></reason>",
+        assertReasonXml("<reason><gone/></reason>",
-                JingleReason.Gone.toXML().toString());
+                JingleReason.Gone);
-        assertEquals("<reason><media-error/></reason>",
+        assertReasonXml("<reason><media-error/></reason>",
-                JingleReason.MediaError.toXML().toString());
+                JingleReason.MediaError);
-        assertEquals("<reason><security-error/></reason>",
+        assertReasonXml("<reason><security-error/></reason>",
-                JingleReason.SecurityError.toXML().toString());
+                JingleReason.SecurityError);
-        assertEquals("<reason><unsupported-applications/></reason>",
+        assertReasonXml("<reason><unsupported-applications/></reason>",
-                JingleReason.UnsupportedApplications.toXML().toString());
+                JingleReason.UnsupportedApplications);
-        assertEquals("<reason><timeout/></reason>",
+        assertReasonXml("<reason><timeout/></reason>",
-                JingleReason.Timeout.toXML().toString());
+                JingleReason.Timeout);
-        assertEquals("<reason><failed-application/></reason>",
+        assertReasonXml("<reason><failed-application/></reason>",
-                JingleReason.FailedApplication.toXML().toString());
+                JingleReason.FailedApplication);
-        assertEquals("<reason><incompatible-parameters/></reason>",
+        assertReasonXml("<reason><incompatible-parameters/></reason>",
-                JingleReason.IncompatibleParameters.toXML().toString());
+                JingleReason.IncompatibleParameters);
-        assertEquals("<reason><alternative-session><sid>1234</sid></alternative-session></reason>",
+        assertReasonXml("<reason><alternative-session><sid>1234</sid></alternative-session></reason>",
-                JingleReason.AlternativeSession("1234").toXML().toString());
+                JingleReason.AlternativeSession("1234"));
     }
 
-    @Test(expected = NullPointerException.class)
+    private static void assertReasonXml(String expected, JingleReason reason) {
+        String actualXml = reason.toXML(JingleReason.NAMESPACE).toString();
+        assertEquals(expected, actualXml);
+    }
+
+    @Test
     public void alternativeSessionEmptyStringTest() {
-        // Alternative sessionID must not be empty
+        assertThrows(NullPointerException.class, () ->
-        JingleReason.AlternativeSession("");
+            // Alternative sessionID must not be empty
+            JingleReason.AlternativeSession("")
+        );
     }
 
-    @Test(expected = NullPointerException.class)
+    @Test
     public void alternativeSessionNullStringTest() {
-        // Alternative sessionID must not be null
+        assertThrows(NullPointerException.class, () ->
-        JingleReason.AlternativeSession(null);
+            // Alternative sessionID must not be null
+            JingleReason.AlternativeSession(null)
+        );
     }
 
-    @Test(expected = IllegalArgumentException.class)
+    @Test
     public void illegalArgumentTest() {
-        JingleReason.Reason.fromString("illegal-reason");
+        assertThrows(IllegalArgumentException.class, () ->
+            JingleReason.Reason.fromString("illegal-reason")
+        );
     }
 }

smack-im/src/main/java/org/jivesoftware/smack/roster/packet/RosterPacket.java

@@ -24,8 +24,8 @@ import java.util.Locale;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArraySet;
 
+import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.packet.IQ;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.packet.Stanza;
 import org.jivesoftware.smack.util.EqualsUtil;
 import org.jivesoftware.smack.util.HashCode;
@@ -112,7 +112,7 @@ public final class RosterPacket extends IQ {
      * the groups the roster item belongs to.
      */
     // TODO Make this class immutable.
-    public static final class Item implements NamedElement {
+    public static final class Item implements ExtensionElement {
 
         /**
          * The constant value "{@value}".
@@ -163,6 +163,11 @@ public final class RosterPacket extends IQ {
             return ELEMENT;
         }
 
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
+
         /**
          * Returns the user.
          *
@@ -275,7 +280,7 @@ public final class RosterPacket extends IQ {
 
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this);
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
             xml.attribute("jid", jid);
             xml.optAttribute("name", name);
             xml.optAttribute("subscription", itemType);

smack-jingle-old/src/main/java/org/jivesoftware/smackx/jingleold/packet/Jingle.java

@@ -182,25 +182,6 @@ public class Jingle extends IQ {
         return sid;
     }
 
-    /**
-     * Returns the XML element name of the extension sub-packet root element.
-     * Always returns "jingle"
-     *
-     * @return the XML element name of the stanza extension.
-     */
-    public static String getElementName() {
-        return NODENAME;
-    }
-
-    /**
-     * Returns the XML namespace of the extension sub-packet root element.
-     *
-     * @return the XML namespace of the stanza extension.
-     */
-    public static String getNamespace() {
-        return NAMESPACE;
-    }
-
     /**
      * Jingle content info.
      *

smack-jingle-old/src/main/java/org/jivesoftware/smackx/jingleold/provider/JingleProvider.java

@@ -120,7 +120,7 @@ public class JingleProvider extends IQProvider<Jingle> {
                 }
 
             } else if (eventType == XmlPullParser.Event.END_ELEMENT) {
-                if (parser.getName().equals(Jingle.getElementName())) {
+                if (parser.getName().equals(Jingle.NODENAME)) {
                     done = true;
                 }
             }

smack-legacy/src/main/java/org/jivesoftware/smackx/workgroup/packet/AgentStatusRequest.java

@@ -65,14 +65,6 @@ public class AgentStatusRequest extends IQ {
         return Collections.unmodifiableSet(agents);
     }
 
-    public String getElementName() {
-        return ELEMENT_NAME;
-    }
-
-    public String getNamespace() {
-        return NAMESPACE;
-    }
-
     @Override
     protected IQChildElementXmlStringBuilder getIQChildElementBuilder(IQChildElementXmlStringBuilder buf) {
         buf.rightAngleBracket();

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/element/OmemoElement.java

@@ -76,7 +76,7 @@ public abstract class OmemoElement implements ExtensionElement {
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
         XmlStringBuilder sb = new XmlStringBuilder(this, enclosingNamespace).rightAngleBracket();
 
-        sb.element(header);
+        sb.append(header);
 
         if (payload != null) {
             sb.openElement(ATTR_PAYLOAD).append(Base64.encodeToString(payload)).closeElement(ATTR_PAYLOAD);

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/element/OmemoHeaderElement.java

@@ -19,17 +19,22 @@ package org.jivesoftware.smackx.omemo.element;
 import java.util.ArrayList;
 import java.util.List;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 import org.jivesoftware.smack.util.stringencoder.Base64;
 
+import org.jivesoftware.smackx.omemo.util.OmemoConstants;
+
 /**
  * Header element of the message. The header contains information about the sender and the encrypted keys for
  * the recipients, as well as the iv element for AES.
  */
-public abstract class OmemoHeaderElement implements NamedElement {
+public abstract class OmemoHeaderElement implements FullyQualifiedElement {
+
+    public static final String ELEMENT = "header";
+    public static final String NAMESPACE = OmemoConstants.OMEMO_NAMESPACE_V_AXOLOTL;
 
-    public static final String NAME_HEADER = "header";
     public static final String ATTR_SID = "sid";
     public static final String ATTR_IV = "iv";
 
@@ -62,16 +67,21 @@ public abstract class OmemoHeaderElement implements NamedElement {
 
     @Override
     public String getElementName() {
-        return NAME_HEADER;
+        return ELEMENT;
     }
 
     @Override
-    public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder sb = new XmlStringBuilder(this);
+        return NAMESPACE;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
+        XmlStringBuilder sb = new XmlStringBuilder(this, enclosingXmlEnvironment);
         sb.attribute(ATTR_SID, getSid()).rightAngleBracket();
 
         for (OmemoKeyElement k : getKeys()) {
-            sb.element(k);
+            sb.append(k);
         }
 
         sb.openElement(ATTR_IV).append(Base64.encodeToString(getIv())).closeElement(ATTR_IV);

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/element/OmemoKeyElement.java

@@ -16,16 +16,21 @@
  */
 package org.jivesoftware.smackx.omemo.element;
 
-import org.jivesoftware.smack.packet.NamedElement;
+import org.jivesoftware.smack.packet.FullyQualifiedElement;
+import org.jivesoftware.smack.packet.XmlEnvironment;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 import org.jivesoftware.smack.util.stringencoder.Base64;
 
+import org.jivesoftware.smackx.omemo.util.OmemoConstants;
+
 /**
  * Small class to collect key (byte[]), its id and whether its a preKey or not.
  */
-public class OmemoKeyElement implements NamedElement {
+public class OmemoKeyElement implements FullyQualifiedElement {
+
+    public static final String ELEMENT = "key";
+    public static final String NAMESPACE = OmemoConstants.OMEMO_NAMESPACE_V_AXOLOTL;
 
-    public static final String NAME_KEY = "key";
     public static final String ATTR_RID = "rid";
     public static final String ATTR_PREKEY = "prekey";
 
@@ -34,9 +39,7 @@ public class OmemoKeyElement implements NamedElement {
     private final boolean preKey;
 
     public OmemoKeyElement(byte[] data, int id) {
-        this.data = data;
+        this(data, id, false);
-        this.id = id;
-        this.preKey = false;
     }
 
     public OmemoKeyElement(byte[] data, int id, boolean preKey) {
@@ -64,12 +67,17 @@ public class OmemoKeyElement implements NamedElement {
 
     @Override
     public String getElementName() {
-        return NAME_KEY;
+        return ELEMENT;
     }
 
     @Override
-    public CharSequence toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
+    public String getNamespace() {
-        XmlStringBuilder sb = new XmlStringBuilder(this);
+        return NAMESPACE;
+    }
+
+    @Override
+    public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
+        XmlStringBuilder sb = new XmlStringBuilder(this, enclosingXmlEnvironment);
 
         if (isPreKey()) {
             sb.attribute(ATTR_PREKEY, true);

smack-omemo/src/main/java/org/jivesoftware/smackx/omemo/provider/OmemoVAxolotlProvider.java

@@ -54,14 +54,14 @@ public class OmemoVAxolotlProvider extends ExtensionElementProvider<OmemoElement
             switch (tag) {
                 case START_ELEMENT:
                     switch (name) {
-                        case OmemoHeaderElement.NAME_HEADER:
+                        case OmemoHeaderElement.ELEMENT:
                             for (int i = 0; i < parser.getAttributeCount(); i++) {
                                 if (parser.getAttributeName(i).equals(OmemoHeaderElement.ATTR_SID)) {
                                     sid = Integer.parseInt(parser.getAttributeValue(i));
                                 }
                             }
                             break;
-                        case OmemoKeyElement.NAME_KEY:
+                        case OmemoKeyElement.ELEMENT:
                             boolean prekey = false;
                             int rid = -1;
                             for (int i = 0; i < parser.getAttributeCount(); i++) {

smack-openpgp/src/main/java/org/jivesoftware/smackx/ox/element/PubkeyElement.java

@@ -20,7 +20,6 @@ import java.nio.charset.Charset;
 import java.util.Date;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -77,7 +76,7 @@ public class PubkeyElement implements ExtensionElement {
         XmlStringBuilder xml = new XmlStringBuilder(this)
                 .optAttribute(ATTR_DATE, date)
                 .rightAngleBracket()
-                .element(getDataElement())
+                .append(getDataElement())
                 .closeElement(this);
         return xml;
     }
@@ -85,7 +84,7 @@ public class PubkeyElement implements ExtensionElement {
     /**
      * Element that contains the base64 encoded public key.
      */
-    public static class PubkeyDataElement implements NamedElement {
+    public static class PubkeyDataElement implements ExtensionElement {
 
         public static final String ELEMENT = "data";
 
@@ -109,9 +108,14 @@ public class PubkeyElement implements ExtensionElement {
             return ELEMENT;
         }
 
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
+
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
-            XmlStringBuilder xml = new XmlStringBuilder(this)
+            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace)
                     .rightAngleBracket()
                     .append(new String(b64Data, Charset.forName("UTF-8")))
                     .closeElement(this);

smack-openpgp/src/main/java/org/jivesoftware/smackx/ox/element/PublicKeysListElement.java

@@ -22,7 +22,6 @@ import java.util.Map;
 import java.util.TreeMap;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
-import org.jivesoftware.smack.packet.NamedElement;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -66,9 +65,7 @@ public final class PublicKeysListElement implements ExtensionElement {
     @Override
     public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
         XmlStringBuilder xml = new XmlStringBuilder(this).rightAngleBracket();
-        for (PubkeyMetadataElement metadataElement : metadata.values()) {
+        xml.append(metadata.values());
-            xml.element(metadataElement);
-        }
         xml.closeElement(this);
         return xml;
     }
@@ -92,7 +89,7 @@ public final class PublicKeysListElement implements ExtensionElement {
         }
     }
 
-    public static class PubkeyMetadataElement implements NamedElement {
+    public static class PubkeyMetadataElement implements ExtensionElement {
 
         public static final String ELEMENT = "pubkey-metadata";
         public static final String ATTR_V4_FINGERPRINT = "v4-fingerprint";
@@ -123,6 +120,11 @@ public final class PublicKeysListElement implements ExtensionElement {
             return ELEMENT;
         }
 
+        @Override
+        public String getNamespace() {
+            return NAMESPACE;
+        }
+
         @Override
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
             XmlStringBuilder xml = new XmlStringBuilder(this)

smack-tcp/src/test/java/org/jivesoftware/smack/sm/provider/ParseStreamManagementTest.java

@@ -122,7 +122,7 @@ public class ParseStreamManagementTest {
 
         StanzaErrorTextElement textElement = textElements.get(0);
         assertEquals("Previous session timed out", textElement.getText());
-        assertEquals("en", textElement.getLang());
+        assertEquals("en", textElement.getLanguage());
     }
 
     @Test