Improve OX's PubkeyElement

there is no reason why we want to store the bytes of the base64
encoded string. Simply store the string itself.

Also add a convenience method to get the decoded bytes of the PubKey.

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

@@ -636,7 +636,8 @@ public final class OpenPgpManager extends Manager {
      * @return {@link PubkeyElement} containing the key
      */
     private static PubkeyElement createPubkeyElement(byte[] bytes, Date date) {
-        return new PubkeyElement(new PubkeyElement.PubkeyDataElement(Base64.encode(bytes)), date);
+        String base64EncodedOpenPgpPubKey = Base64.encodeToString(bytes);
+        return new PubkeyElement(new PubkeyElement.PubkeyDataElement(base64EncodedOpenPgpPubKey), date);
     }
 
     /**

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

@@ -16,12 +16,12 @@
  */
 package org.jivesoftware.smackx.ox.element;
 
-import java.nio.charset.Charset;
 import java.util.Date;
 
 import org.jivesoftware.smack.packet.ExtensionElement;
 import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.XmlStringBuilder;
+import org.jivesoftware.smack.util.stringencoder.Base64;
 
 /**
  * Class representing a pubkey element which is used to transport OpenPGP public keys.
@@ -88,21 +88,30 @@ public class PubkeyElement implements ExtensionElement {
 
         public static final String ELEMENT = "data";
 
-        private final byte[] b64Data;
+        private final String b64Data;
 
-        public PubkeyDataElement(byte[] b64Data) {
+        public PubkeyDataElement(String b64Data) {
             this.b64Data = Objects.requireNonNull(b64Data);
         }
 
         /**
          * Base64 encoded public key.
          *
-         * @return public key bytes.
+         * @return the base64 encoded version of the public key.
          */
-        public byte[] getB64Data() {
+        public String getB64Data() {
             return b64Data;
         }
 
+        private transient byte[] pubKeyBytesCache;
+
+        public byte[] getPubKeyBytes() {
+            if (pubKeyBytesCache == null) {
+                pubKeyBytesCache = Base64.decode(b64Data);
+            }
+            return pubKeyBytesCache.clone();
+        }
+
         @Override
         public String getElementName() {
             return ELEMENT;
@@ -117,7 +126,7 @@ public class PubkeyElement implements ExtensionElement {
         public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
             XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace)
                     .rightAngleBracket()
-                    .append(new String(b64Data, Charset.forName("UTF-8")))
+                    .append(b64Data)
                     .closeElement(this);
             return xml;
         }

smack-openpgp/src/main/java/org/jivesoftware/smackx/ox/provider/PubkeyElementProvider.java

@@ -17,7 +17,6 @@
 package org.jivesoftware.smackx.ox.provider;
 
 import java.io.IOException;
-import java.nio.charset.Charset;
 import java.util.Date;
 
 import org.jivesoftware.smack.packet.XmlEnvironment;
@@ -34,7 +33,7 @@ import org.jivesoftware.smackx.ox.element.PubkeyElement;
  */
 public class PubkeyElementProvider extends ExtensionElementProvider<PubkeyElement> {
 
-    public static final PubkeyElementProvider TEST_INSTANCE = new PubkeyElementProvider();
+    public static final PubkeyElementProvider INSTANCE = new PubkeyElementProvider();
 
     @Override
     public PubkeyElement parse(XmlPullParser parser, int initialDepth, XmlEnvironment xmlEnvironment) throws XmlPullParserException, IOException, SmackTextParseException {
@@ -46,11 +45,9 @@ public class PubkeyElementProvider extends ExtensionElementProvider<PubkeyElemen
             if (tag == XmlPullParser.Event.START_ELEMENT) {
                 switch (name) {
                     case PubkeyElement.PubkeyDataElement.ELEMENT:
-                        String data = parser.nextText();
-                        if (data != null) {
-                            byte[] bytes = data.getBytes(Charset.forName("UTF-8"));
-                            return new PubkeyElement(new PubkeyElement.PubkeyDataElement(bytes), date);
-                        }
+                        String base64EncodedOpenPgpPubKey = parser.nextText();
+                        PubkeyElement.PubkeyDataElement pubkeyDataElement = new PubkeyElement.PubkeyDataElement(base64EncodedOpenPgpPubKey);
+                        return new PubkeyElement(pubkeyDataElement, date);
                 }
             }
         }

smack-openpgp/src/test/java/org/jivesoftware/smackx/ox/PubkeyElementTest.java

@@ -17,44 +17,48 @@
 package org.jivesoftware.smackx.ox;
 
 import static junit.framework.TestCase.assertEquals;
-import static junit.framework.TestCase.assertTrue;
 import static org.jivesoftware.smack.test.util.XmlUnitUtils.assertXmlSimilar;
 
-import java.nio.charset.Charset;
-import java.util.Arrays;
+import java.io.IOException;
+import java.text.ParseException;
 import java.util.Date;
 
+import org.jivesoftware.smack.parsing.SmackParsingException;
 import org.jivesoftware.smack.test.util.SmackTestSuite;
-import org.jivesoftware.smack.test.util.TestUtils;
+import org.jivesoftware.smack.test.util.SmackTestUtil;
 import org.jivesoftware.smack.xml.XmlPullParser;
+import org.jivesoftware.smack.xml.XmlPullParserException;
 
 import org.jivesoftware.smackx.ox.element.PubkeyElement;
 import org.jivesoftware.smackx.ox.provider.PubkeyElementProvider;
 
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
 import org.jxmpp.util.XmppDateTime;
 
 public class PubkeyElementTest extends SmackTestSuite {
 
-    @Test
-    public void providerTest() throws Exception {
-        String expected =
+    @ParameterizedTest
+    @EnumSource(SmackTestUtil.XmlPullParserKind.class)
+    public void providerTest(SmackTestUtil.XmlPullParserKind parserKind)
+                    throws ParseException, XmlPullParserException, IOException, SmackParsingException {
+        String base64EncodedOpenPgpPublicKey = "VGhpcyBpcyBqdXN0IGEgdGVzdA==";
+        String pubkeyElement =
                 "<pubkey xmlns='urn:xmpp:openpgp:0' date='2018-01-21T10:46:21.000+00:00'>" +
                 "<data>" +
-                "BASE64_OPENPGP_PUBLIC_KEY" +
+                base64EncodedOpenPgpPublicKey +
                 "</data>" +
                 "</pubkey>";
 
         Date date = XmppDateTime.parseXEP0082Date("2018-01-21T10:46:21.000+00:00");
-        byte[] key = "BASE64_OPENPGP_PUBLIC_KEY".getBytes(Charset.forName("UTF-8"));
-        PubkeyElement element = new PubkeyElement(new PubkeyElement.PubkeyDataElement(key), date);
+        PubkeyElement element = new PubkeyElement(new PubkeyElement.PubkeyDataElement(base64EncodedOpenPgpPublicKey), date);
 
-        assertXmlSimilar(expected, element.toXML().toString());
+        assertXmlSimilar(pubkeyElement, element.toXML().toString());
 
-        XmlPullParser parser = TestUtils.getParser(expected);
-        PubkeyElement parsed = PubkeyElementProvider.TEST_INSTANCE.parse(parser);
+        XmlPullParser parser = SmackTestUtil.getParserFor(pubkeyElement, parserKind);
+        PubkeyElement parsed = PubkeyElementProvider.INSTANCE.parse(parser);
 
         assertEquals(element.getDate(), parsed.getDate());
-        assertTrue(Arrays.equals(element.getDataElement().getB64Data(), parsed.getDataElement().getB64Data()));
+        assertEquals(element.getDataElement().getB64Data(), parsed.getDataElement().getB64Data());
     }
 }