Partial fix/workaround for #489: add TypeFactory.clearCache()

Author: cowtowncoder

release-notes/VERSION

@@ -5,6 +5,8 @@ Version: 2.4.1 (xx-Jun-2014)
  (reported by huxi@github)
 #482: Make date parsing error behavior consistent with JDK
  (suggested by Steve S, sanbeg@github)
+#489 (partial): TypeFactory cache prevents garbage collection of custom ClassLoader
+ (reported by sftwrengnr@github)
 
 ------------------------------------------------------------------------
 === History: ===

src/main/java/com/fasterxml/jackson/databind/type/TypeFactory.java

@@ -115,6 +115,9 @@ protected TypeFactory(TypeParser p, TypeModifier[] mods) {
 
     public TypeFactory withModifier(TypeModifier mod) 
     {
+        if (mod == null) { // mostly for unit tests
+            return new TypeFactory(_parser, _modifiers);
+        }
         if (_modifiers == null) {
             return new TypeFactory(_parser, new TypeModifier[] { mod });
         }
@@ -128,6 +131,20 @@ public TypeFactory withModifier(TypeModifier mod)
      */
     public static TypeFactory defaultInstance() { return instance; }
 
+    /**
+     * Method that will clear up any cached type definitions that may
+     * be cached by this {@link TypeFactory} instance.
+     * This method should not be commonly used, that is, only use it
+     * if you know there is a problem with retention of type definitions;
+     * the most likely (and currently only known) problem is retention
+     * of {@link Class} instances via {@link JavaType} reference.
+     * 
+     * @since 2.4.1
+     */
+    public void clearCache() {
+        _typeCache.clear();
+    }
+    
     /*
     /**********************************************************
     /* Static methods for non-instance-specific functionality

src/main/java/com/fasterxml/jackson/databind/util/LRUMap.java

@@ -80,6 +80,21 @@ public V remove(Object key) {
             _writeLock.unlock();
         }
     }
+
+    /**
+     * Overridden to allow concurrent way of removing all cached entries.
+     * 
+     * @since 2.4.1
+     */
+    @Override
+    public void clear() {
+        _writeLock.lock();
+        try {
+            super.clear();
+        } finally {
+            _writeLock.unlock();
+        }
+    }
 
     /*
     /**********************************************************

src/test/java/com/fasterxml/jackson/databind/type/TestTypeFactory.java

@@ -193,8 +193,6 @@ public void testIterator()
     /**
      * Test for verifying that parametric types can be constructed
      * programmatically
-     * 
-     * @since 1.5
      */
     public void testParametricTypes()
     {
@@ -277,10 +275,7 @@ public void testCanonicalNames()
     /* Unit tests: low-level inheritance resolution
     /**********************************************************
      */
-    
-    /**
-     * @since 1.6
-     */
+
     public void testSuperTypeDetectionClass()
     {
         TypeFactory tf = TypeFactory.defaultInstance();
@@ -294,10 +289,7 @@ public void testSuperTypeDetectionClass()
         assertSame(HashMap.class, sup2.getRawClass());
         assertNull(sup2.getSuperType());
     }
-    
-    /**
-     * @since 1.6
-     */
+
     public void testSuperTypeDetectionInterface()
     {
         // List first
@@ -324,9 +316,6 @@ public void testSuperTypeDetectionInterface()
         assertNull(sup2.getSuperType());
     }
 
-    /**
-     * @since 1.6
-     */
     public void testAtomicArrayRefParameterDetection()
     {
         TypeFactory tf = TypeFactory.defaultInstance();
@@ -352,10 +341,7 @@ private int _countSupers(HierarchicType t)
     /* Unit tests: map/collection type parameter resolution
     /**********************************************************
      */
-    
-    /**
-     * @since 1.6
-     */
+
     public void testMapTypesSimple()
     {
         TypeFactory tf = TypeFactory.defaultInstance();
@@ -365,9 +351,6 @@ public void testMapTypesSimple()
         assertEquals(tf.constructType(Boolean.class), mapType.getContentType());
     }
 
-    /**
-     * @since 1.6
-     */
     public void testMapTypesRaw()
     {
         TypeFactory tf = TypeFactory.defaultInstance();
@@ -377,9 +360,6 @@ public void testMapTypesRaw()
         assertEquals(tf.constructType(Object.class), mapType.getContentType());        
     }
 
-    /**
-     * @since 1.6
-     */
     public void testMapTypesAdvanced()
     {
         TypeFactory tf = TypeFactory.defaultInstance();
@@ -402,8 +382,6 @@ public void testMapTypesAdvanced()
     /**
      * Specific test to verify that complicate name mangling schemes
      * do not fool type resolver
-     * 
-     * @since 1.6
      */
     public void testMapTypesSneaky()
     {
@@ -416,8 +394,6 @@ public void testMapTypesSneaky()
 
     /**
      * Plus sneaky types may be found via introspection as well.
-     * 
-     * @since 1.7
      */
     public void testSneakyFieldTypes() throws Exception
     {
@@ -438,8 +414,6 @@ public void testSneakyFieldTypes() throws Exception
 
     /**
      * Looks like type handling actually differs for properties, too.
-     * 
-     * @since 1.7
      */
     public void testSneakyBeanProperties() throws Exception
     {
@@ -533,5 +507,16 @@ public void testMoreSpecificType()
         assertSame(t1, tf.moreSpecificType(t1, t2));
         assertSame(t2, tf.moreSpecificType(t2, t1));
     }
+
+    // [Issue#489]
+    public void testCacheClearing()
+    {
+        TypeFactory tf = TypeFactory.defaultInstance().withModifier(null);
+        assertEquals(0, tf._typeCache.size());
+        tf.constructType(getClass());
+        assertEquals(1, tf._typeCache.size());
+        tf.clearCache();
+        assertEquals(0, tf._typeCache.size());
+    }
 }