2 * Copyright 2005-2010 the original author or authors.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
16 package org.wamblee.general;
18 import java.lang.reflect.InvocationHandler;
19 import java.lang.reflect.InvocationTargetException;
20 import java.lang.reflect.Method;
21 import java.lang.reflect.Proxy;
24 * Thread-specific proxy is used to create implementations of interfaces that
25 * delegate to a thread-specific implementation of the service.
27 * It can be used for instance to create a contextual reference to an entity manager
28 * that delegates to a thread-specific instance.
30 * The {@link #set(Object)} method sets the current service instance for the current thread.
31 * The {@link #get()} method gets the current service instance for the current thread.
32 * The {@link #getProxy()} method gets a proxy that will delegate at runtime to the thread-specific
33 * instance. The result from this method can be passed at construction of an object that will be used
34 * by multiple threads.
36 * This class is mostly used by infrastructure code (utilities) and test tools.
40 * @author Erik Brakkee
43 public class ThreadSpecificProxyFactory<T> {
44 private class ThreadSpecificInvocationHandler implements InvocationHandler {
47 public Object invoke(Object aProxy, Method aMethod, Object[] aArgs)
50 return aMethod.invoke(svc.get(), aArgs);
51 } catch (InvocationTargetException e) {
57 private ThreadLocal<T> svc;
62 * Constructs the factory.
65 * Interface class of the service to proxy.
67 public ThreadSpecificProxyFactory(Class<T> aClass) {
68 if (!aClass.isInterface()) {
69 throw new IllegalArgumentException("Class " + aClass.getName() +
70 " is not an interface");
72 svc = new ThreadLocal<T>();
74 proxy = createProxy();
78 * Sets the thread-specific service.
81 * Service, use null value to reset.
83 public void set(T aService) {
88 * Gets the current thread-specific service.
89 * To get a contextual reference that can be used by any thread but delegates to a thread-specific
90 * instance, use {@link #getProxy()}.
98 * Gets the proxy that delegates to the thread-specific instance set by
99 * {@link #set(Object)}
103 public T getProxy() {
107 private T createProxy() {
108 InvocationHandler handler = new ThreadSpecificInvocationHandler();
109 Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
110 new Class[] { clazz });
113 proxyObj = (T) proxyClass.getConstructor(
114 new Class[] { InvocationHandler.class }).newInstance(
115 new Object[] { handler });
117 } catch (Exception e) {
118 throw new RuntimeException("Could not create proxy for " +