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[utils] / support / general / src / main / java / org / wamblee / general / SerializableInvocationHandler.java

diff --git a/support/general/src/main/java/org/wamblee/general/SerializableInvocationHandler.java b/support/general/src/main/java/org/wamblee/general/SerializableInvocationHandler.java
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+/*
+ * Copyright 2005-2010 the original author or authors.
+ * 
+ * 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.wamblee.general;
+
+import java.io.Serializable;
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Serialiable invocation handler that delegate to a possibly non-serializable object.
+ * The trick is to store the object in a static map with a unique id and use the id to 
+ * retrieve the object instead of storing the object. 
+ * 
+ * @author Erik Brakkee
+ *
+ * @param <T>
+ */
+class SerializableInvocationHandler<T> implements InvocationHandler,
+    Serializable {
+
+    /**
+     * We store a map of unique ids of invocation handlers to thread local
+     * storage of the service. In this way, serialiability of the generated
+     * proxy is obtained (required by framweorks such as wicket). Also,
+     * different factories will still be separate and never use the same
+     * threadlocal storage.
+     */
+    private static Map<Integer, Object> STORAGE = new ConcurrentHashMap<Integer, Object>();
+
+    private static AtomicInteger COUNTER = new AtomicInteger();
+
+    private int id;
+    private Class clazz;
+
+    /**
+     * Constructs the handler.
+     * 
+     * @param aSvc
+     *            Thread local for the service.
+     * @param aClass
+     *            Service interface class.
+     */
+    public SerializableInvocationHandler(T aSvc, Class aClass) {
+        id = COUNTER.incrementAndGet();
+        clazz = aClass;
+        STORAGE.put(id, aSvc);
+    }
+
+    @Override
+    public Object invoke(Object aProxy, Method aMethod, Object[] aArgs)
+        throws Throwable {
+
+        T local = (T)STORAGE.get(id);
+        try {
+            return aMethod.invoke(local, aArgs);
+        } catch (InvocationTargetException e) {
+            throw e.getCause();
+        }
+    }
+}
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