动态代理 java

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本文介绍了一种使用Java反射API实现的动态代理模式，通过创建InvocationHandler实例并利用Proxy类提供的newProxyInstance方法来生成代理对象。该模式允许在不修改原始类的基础上增加额外的功能，例如在方法调用前后记录日志。

代理工具类

/**
 * created on Jan 13, 2010 9:34:18 AM  *
 * Copyright 2001-2010 The Apache Software Foundation.
 * 
 * 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 dynamicProxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Date;

/**
 * @author * 
 */
public class DynamicLogger implements InvocationHandler {

    private Object target;


    public Object newProxyObject(Object target) { // 在JVM中动态生成代理类
        this.target = target;
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
    }

    public  DynamicLogger() {
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object,
     *      java.lang.reflect.Method, java.lang.Object[])
     */
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        before();
        System.out.println("invoke method is "+method.getName());
        Object result = method.invoke(target, args);
        after();
        // System.out.println(proxy);
        return result;
    }

    private void before() {
        System.out.println("now is " +new Date());
    }

    private void after() {
        System.out.println("now is " +new Date());
    }
}

接口

public interface IPerson {

    void speak();
    
    void walk();
}

实现

public class RealPerson implements IPerson {

    private String name;
    
    /**
     * @param name
     */
    public RealPerson(String name) {
        super();
        this.name = name;
    }

    /*
     * (non-Javadoc)
     * 
     * @see dynamicProxy.IPerson#speak()
     */
    public void speak() {
        System.out.println(name+ " is speak");
    }

    /*
     * (non-Javadoc)
     * 
     * @see dynamicProxy.IPerson#walk()
     */
    public void walk() {
        System.out.println(name+ " is walk");
    }

}

测试

public class Client extends TestCase {
    public void testProxy() throws Exception {
        IPerson Warrior=new RealPerson("Warrior");
        IPerson Priest=new RealPerson("Priest");
        DynamicLogger log1=new DynamicLogger();
        DynamicLogger log2=new DynamicLogger();
        IPerson proxyWarrior=(IPerson) log1.newProxyObject(Warrior);
        IPerson proxyPriest=(IPerson) log2.newProxyObject(Priest);
        proxyWarrior.walk();
        proxyWarrior.speak();
        System.out.println("====");
        proxyPriest.walk();
        proxyPriest.speak();
    }
}

输出

now is Wed Jan 13 10:05:59 CST 2010
invoke method is walk
Warrior is walk
now is Wed Jan 13 10:05:59 CST 2010
now is Wed Jan 13 10:05:59 CST 2010
invoke method is speak
Warrior is speak
now is Wed Jan 13 10:05:59 CST 2010
====
now is Wed Jan 13 10:05:59 CST 2010
invoke method is walk
Priest is walk
now is Wed Jan 13 10:05:59 CST 2010
now is Wed Jan 13 10:05:59 CST 2010
invoke method is speak
Priest is speak
now is Wed Jan 13 10:05:59 CST 2010