SmackDebugger initialization moved to dedicated factory.

You can set your custom debugger class as before, by using clear api
method ReflectionDebuggerFactory.setDebuggerClass, or you can set custom
debugger factory using SmackConfiguration.setDebuggerFactory if it's not
enough flexible for your needs

smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java

@@ -19,7 +19,6 @@ package org.jivesoftware.smack;
 import java.io.IOException;
 import java.io.Reader;
 import java.io.Writer;
-import java.lang.reflect.Constructor;
 import java.util.Collection;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -54,16 +53,6 @@ import org.jivesoftware.smack.rosterstore.RosterStore;
 public abstract class AbstractXMPPConnection implements XMPPConnection {
     private static final Logger LOGGER = Logger.getLogger(AbstractXMPPConnection.class.getName());
 
-    /**
-     * Possible default debugger implementations. The order of enumeration is the one in which we try
-     * to instantiate these.
-     */
-    private static final String[] DEBUGGERS = new String[] {
-                    "org.jivesoftware.smackx.debugger.EnhancedDebugger",
-                    "org.jivesoftware.smackx.debugger.android.AndroidDebugger",
-                    "org.jivesoftware.smack.debugger.LiteDebugger",
-                    "org.jivesoftware.smack.debugger.ConsoleDebugger" };
-
     /** 
      * Counter to uniquely identify connections that are created.
      */
@@ -798,62 +787,12 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
         // If debugging is enabled, we open a window and write out all network traffic.
         if (config.isDebuggerEnabled()) {
             if (debugger == null) {
-                // Detect the debugger class to use.
+                debugger = SmackConfiguration.createDebugger(this, writer, reader);
-                String className = null;
-                // Use try block since we may not have permission to get a system
-                // property (for example, when an applet).
-                try {
-                    className = System.getProperty("smack.debuggerClass");
             }
-                catch (Throwable t) {
+
-                    // Ignore.
+            if (debugger == null) {
-                }
-                Class<?> debuggerClass = null;
-                if (className != null) {
-                    try {
-                        debuggerClass = Class.forName(className);
-                    }
-                    catch (Exception e) {
-                        LOGGER.warning("Unabled to instantiate debugger class " + className);
-                    }
-                }
-                if (debuggerClass == null) {
-                    for (String debugger : DEBUGGERS) {
-                        try {
-                            debuggerClass = Class.forName(debugger);
-                        }
-                        catch (ClassNotFoundException cnfe) {
-                            LOGGER.fine("Did not find debugger class '" + debugger + "'");
-                        }
-                        catch (Exception ex) {
-                            LOGGER.warning("Unabled to instantiate either Smack debugger class");
-                        }
-                        if (debuggerClass != null) {
-                            // We found a debugger, let's use it
-                            break;
-                        }
-                    }
-                }
-                if (debuggerClass != null) {
-                    // Create a new debugger instance. If an exception occurs then disable the
-                    // debugging
-                    // option
-                    try {
-                        Constructor<?> constructor = debuggerClass.getConstructor(
-                                        XMPPConnection.class, Writer.class, Reader.class);
-                        debugger = (SmackDebugger) constructor.newInstance(this, writer, reader);
-                        reader = debugger.getReader();
-                        writer = debugger.getWriter();
-                    }
-                    catch (Exception e) {
-                        throw new IllegalArgumentException(
-                                        "Can't initialize the configured debugger!", e);
-                    }
-                } else {
                 LOGGER.severe("Debugging enabled but could not find debugger class");
-                }
+            } else {
-            }
-            else {
                 // Obtain new reader and writer from the existing debugger
                 reader = debugger.newConnectionReader(reader);
                 writer = debugger.newConnectionWriter(writer);

smack-core/src/main/java/org/jivesoftware/smack/SmackConfiguration.java

@@ -21,6 +21,8 @@ import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.Reader;
+import java.io.Writer;
 import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -35,7 +37,9 @@ import javax.net.ssl.HostnameVerifier;
 
 import org.jivesoftware.smack.compression.Java7ZlibInputOutputStream;
 import org.jivesoftware.smack.compression.XMPPInputOutputStream;
+import org.jivesoftware.smack.debugger.ReflectionDebuggerFactory;
 import org.jivesoftware.smack.debugger.SmackDebugger;
+import org.jivesoftware.smack.debugger.SmackDebuggerFactory;
 import org.jivesoftware.smack.initializer.SmackInitializer;
 import org.jivesoftware.smack.parsing.ExceptionThrowingCallback;
 import org.jivesoftware.smack.parsing.ParsingExceptionCallback;
@@ -73,6 +77,8 @@ public final class SmackConfiguration {
 
     private final static List<XMPPInputOutputStream> compressionHandlers = new ArrayList<XMPPInputOutputStream>(2);
 
+    private static SmackDebuggerFactory debuggerFactory = new ReflectionDebuggerFactory();
+
     /**
      * Value that indicates whether debugging is enabled. When enabled, a debug
      * window will apear for each new connection that will contain the following
@@ -258,10 +264,38 @@ public final class SmackConfiguration {
     }
 
     /**
-     * Sets smack debugger class
+     * Sets Smack debugger factory.
+     *
+     * @param debuggerFactory new debugger factory implementation to be used by Smack
      */
-    public static <T extends SmackDebugger> void setDebugger(Class<T> debuggerClass) {
+    public static void setDebuggerFactory(SmackDebuggerFactory debuggerFactory) {
-        System.setProperty("smack.debuggerClass", debuggerClass.getCanonicalName());
+        SmackConfiguration.debuggerFactory = debuggerFactory;
+    }
+
+    /**
+     * @return a debugger factory or <code>null</code>
+     */
+    public static SmackDebuggerFactory getDebuggerFactory() {
+        return debuggerFactory;
+    }
+
+    /**
+     * Creates new debugger instance with given arguments as parameters. May
+     * return <code>null</code> if no DebuggerFactory is set or if the factory
+     * did not produce a debugger.
+     * 
+     * @param connection
+     * @param writer
+     * @param reader
+     * @return a new debugger or <code>null</code>
+     */
+    public static SmackDebugger createDebugger(XMPPConnection connection, Writer writer, Reader reader) {
+        SmackDebuggerFactory factory = getDebuggerFactory();
+        if (factory == null) {
+            return null;
+        } else {
+            return factory.create(connection, writer, reader);
+        }
     }
 
     /**

smack-core/src/main/java/org/jivesoftware/smack/debugger/ReflectionDebuggerFactory.java

@@ -0,0 +1,119 @@
+/**
+ *
+ * Copyright 2014 Vyacheslav Blinov
+ *
+ * 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.smack.debugger;
+
+import org.jivesoftware.smack.XMPPConnection;
+
+import java.io.Reader;
+import java.io.Writer;
+import java.lang.reflect.Constructor;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class ReflectionDebuggerFactory implements SmackDebuggerFactory {
+    private static final Logger LOGGER = Logger.getLogger(ReflectionDebuggerFactory.class.getName());
+    private static final String DEBUGGER_CLASS_PROPERTY_NAME = "smack.debuggerClass";
+
+    /**
+     * Possible default debugger implementations. The order of enumeration is the one in which we try
+     * to instantiate these.
+     */
+    private static final String[] DEFAULT_DEBUGGERS = new String[] {
+            "org.jivesoftware.smackx.debugger.EnhancedDebugger",
+            "org.jivesoftware.smackx.debugger.android.AndroidDebugger",
+            "org.jivesoftware.smack.debugger.LiteDebugger",
+            "org.jivesoftware.smack.debugger.ConsoleDebugger" };
+
+
+    /**
+     * Sets custom debugger class to be created by this factory
+     * @param debuggerClass class to be used by this factory
+     */
+    public static void setDebuggerClass(Class<? extends SmackDebugger> debuggerClass) {
+        if (debuggerClass == null) {
+            System.clearProperty(DEBUGGER_CLASS_PROPERTY_NAME);
+        } else {
+            System.setProperty(DEBUGGER_CLASS_PROPERTY_NAME, debuggerClass.getCanonicalName());
+        }
+    }
+
+    /**
+     * Returns debugger class used by this factory
+     * @return debugger class that will be used for instantiation by this factory
+     */
+    @SuppressWarnings("unchecked")
+    public static Class<SmackDebugger> getDebuggerClass() {
+        String customDebuggerClassName = getCustomDebuggerClassName();
+        if (customDebuggerClassName == null) {
+            return getOneOfDefaultDebuggerClasses();
+        } else {
+            try {
+                return (Class<SmackDebugger>) Class.forName(customDebuggerClassName);
+            } catch (Exception e) {
+                LOGGER.log(Level.WARNING, "Unable to instantiate debugger class " + customDebuggerClassName, e);
+            }
+        }
+        // no suitable debugger class found - give up
+        return null;
+    }
+
+    @Override
+    public SmackDebugger create(XMPPConnection connection, Writer writer, Reader reader) throws IllegalArgumentException {
+        Class<SmackDebugger> debuggerClass = getDebuggerClass();
+        if (debuggerClass != null) {
+            // Create a new debugger instance using 3arg constructor
+            try {
+                Constructor<SmackDebugger> constructor = debuggerClass
+                        .getConstructor(XMPPConnection.class, Writer.class, Reader.class);
+                return constructor.newInstance(connection, writer, reader);
+            } catch (Exception e) {
+                throw new IllegalArgumentException("Can't initialize the configured debugger!", e);
+            }
+        }
+        return null;
+    }
+
+    private static String getCustomDebuggerClassName() {
+        try {
+            // Use try block since we may not have permission to get a system
+            // property (for example, when an applet).
+            return System.getProperty(DEBUGGER_CLASS_PROPERTY_NAME);
+        } catch (Throwable t) {
+            // Ignore.
+            return null;
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Class<SmackDebugger> getOneOfDefaultDebuggerClasses() {
+        for (String debugger : DEFAULT_DEBUGGERS) {
+            try {
+                return (Class<SmackDebugger>) Class.forName(debugger);
+            } catch (ClassNotFoundException cnfe) {
+                LOGGER.fine("Did not find debugger class '" + debugger + "'");
+            } catch (ClassCastException ex) {
+                LOGGER.warning("Found debugger class that does not appears to implement SmackDebugger interface");
+            } catch (Exception ex) {
+                LOGGER.warning("Unable to instantiate either Smack debugger class");
+            }
+        }
+        // did not found any of default debuggers - give up
+        return null;
+    }
+}

smack-core/src/main/java/org/jivesoftware/smack/debugger/SmackDebuggerFactory.java

@@ -0,0 +1,33 @@
+/**
+ *
+ * Copyright 2014 Vyacheslav Blinov
+ *
+ * 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.smack.debugger;
+
+import org.jivesoftware.smack.XMPPConnection;
+
+import java.io.Reader;
+import java.io.Writer;
+
+public interface SmackDebuggerFactory {
+    /**
+     * Initialize the new SmackDebugger instance.
+     *
+     * @throws IllegalArgumentException if the SmackDebugger can't be loaded.
+     */
+    SmackDebugger create(XMPPConnection connection, Writer writer, Reader reader) throws IllegalArgumentException;
+}

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JDebuggerFactory.java

@@ -0,0 +1,35 @@
+/**
+ *
+ * Copyright 2014 Vyacheslav Blinov
+ *
+ * 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.debugger.slf4j;
+
+import org.jivesoftware.smack.XMPPConnection;
+import org.jivesoftware.smack.debugger.SmackDebugger;
+import org.jivesoftware.smack.debugger.SmackDebuggerFactory;
+
+import java.io.Reader;
+import java.io.Writer;
+
+/**
+ * Implementation of SmackDebuggerFactory which always creates instance of SLF4JSmackDebugger
+ */
+public class SLF4JDebuggerFactory implements SmackDebuggerFactory {
+    @Override
+    public SmackDebugger create(XMPPConnection connection, Writer writer, Reader reader) throws IllegalArgumentException {
+        return new SLF4JSmackDebugger(connection, writer, reader);
+    }
+}

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JSmackDebugger.java

@@ -58,7 +58,7 @@ public class SLF4JSmackDebugger implements SmackDebugger  {
      * Makes Smack use this Debugger
      */
     public static void enable() {
-        SmackConfiguration.setDebugger(SLF4JSmackDebugger.class);
+        SmackConfiguration.setDebuggerFactory(new SLF4JDebuggerFactory());
     }
 
     /**