Partial application of the patch in Bugzilla 41044:

 * addition of a generic PropertyCache to be used by all Property
   types that can be safely canonicalized
 * modified EnumProperty, StringProperty, NumberProperty, EnumNumber
   and FixedLength to make use of the cache infrastructure



git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@554251 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 55 insertions, 0 deletions

diff --git a/src/java/org/apache/fop/fo/properties/PropertyCache.java b/src/java/org/apache/fop/fo/properties/PropertyCache.java
new file mode 100644
index 000000000..176cdd4aa
--- /dev/null
+++ b/src/java/org/apache/fop/fo/properties/PropertyCache.java
@@ -0,0 +1,55 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+/* $Id$ */
+
+package org.apache.fop.fo.properties;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.WeakHashMap;
+
+/**
+ *  Thin wrapper around a HashMap to implement the property caching idiom
+ *  in which a new Property instance is created then tested against cached
+ *  instances created previously. If an existing property is found, this is
+ *  retained and the newly created one is instantly eligible for garbage
+ *  collection.
+ */
+public class PropertyCache {
+
+    private Map propCache = Collections.synchronizedMap(new WeakHashMap());
+    
+    
+    /**
+     *  Checks if the given property is present in the cache - if so, returns
+     *  a reference to the cached value. Otherwise the given object is added
+     *  to the cache and returned.
+     *  @param obj
+     *  @return the cached instance
+     */
+    public Property fetch(Property prop) {
+        
+        Property cacheEntry = (Property) propCache.get(prop);
+        if (cacheEntry != null) {
+            return cacheEntry;
+        } else {
+            propCache.put(prop, prop);
+            return prop;
+        }
+    }
+}