Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 908867)
+++ CHANGES.txt	(working copy)
@@ -107,6 +107,11 @@
 * LUCENE-2249: ParallelMultiSearcher should shut down thread pool on
   close.  (Martin Traverso via Uwe Schindler)
   
+* LUCENE-2260: Fixed AttributeSource to not hold a strong
+  reference to the Attribute/AttributeImpl classes which prevents
+  unloading of custom attributes loaded by other classloaders
+  (e.g. in Solr plugins).  (Uwe Schindler)
+
 New features
 
 * LUCENE-2128: Parallelized fetching document frequencies during weight
Index: src/java/org/apache/lucene/util/AttributeSource.java
===================================================================
--- src/java/org/apache/lucene/util/AttributeSource.java	(revision 908867)
+++ src/java/org/apache/lucene/util/AttributeSource.java	(working copy)
@@ -21,7 +21,7 @@
 import java.util.NoSuchElementException;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
-import java.util.IdentityHashMap;
+import java.util.WeakHashMap;
 import java.util.LinkedList;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -54,8 +54,8 @@
     public static final AttributeFactory DEFAULT_ATTRIBUTE_FACTORY = new DefaultAttributeFactory();
     
     private static final class DefaultAttributeFactory extends AttributeFactory {
-      private static final IdentityHashMap<Class<? extends Attribute>, Class<? extends AttributeImpl>> attClassImplMap =
-        new IdentityHashMap<Class<? extends Attribute>, Class<? extends AttributeImpl>>();
+      private static final WeakHashMap<Class<? extends Attribute>, Class<? extends AttributeImpl>> attClassImplMap =
+        new WeakHashMap<Class<? extends Attribute>, Class<? extends AttributeImpl>>();
       
       private DefaultAttributeFactory() {}
     
@@ -173,8 +173,8 @@
   }
   
   /** a cache that stores all interfaces for known implementation classes for performance (slow reflection) */
-  private static final IdentityHashMap<Class<? extends AttributeImpl>,LinkedList<Class<? extends Attribute>>> knownImplClasses =
-    new IdentityHashMap<Class<? extends AttributeImpl>,LinkedList<Class<? extends Attribute>>>();
+  private static final WeakHashMap<Class<? extends AttributeImpl>,LinkedList<Class<? extends Attribute>>> knownImplClasses =
+    new WeakHashMap<Class<? extends AttributeImpl>,LinkedList<Class<? extends Attribute>>>();
   
   /** <b>Expert:</b> Adds a custom AttributeImpl instance with one or more Attribute interfaces.
    * <p><font color="red"><b>Please note:</b> It is not guaranteed, that <code>att</code> is added to
Index: src/java/org/apache/lucene/util/VirtualMethod.java
===================================================================
--- src/java/org/apache/lucene/util/VirtualMethod.java	(revision 908867)
+++ src/java/org/apache/lucene/util/VirtualMethod.java	(working copy)
@@ -20,7 +20,7 @@
 import java.lang.reflect.Method;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.IdentityHashMap;
+import java.util.WeakHashMap;
 import java.util.Set;
 
 /**
@@ -64,8 +64,8 @@
   private final Class<C> baseClass;
   private final String method;
   private final Class<?>[] parameters;
-  private final IdentityHashMap<Class<? extends C>, Integer> cache =
-    new IdentityHashMap<Class<? extends C>, Integer>();
+  private final WeakHashMap<Class<? extends C>, Integer> cache =
+    new WeakHashMap<Class<? extends C>, Integer>();
 
   /**
    * Creates a new instance for the given {@code baseClass} and method declaration.