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java 动态代理

web 2025/7/29 14:58:13

有关Java的动态代理用法，写了一个demo，代码如下：

package com.example.javalib;import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;public class MyClass {public static void main(String[] args) {new MyClass().testProxy();}interface IUserService {void addUser(String username);void deleteUser(int id);String getUser(int id);}private IUserService mUserService = new IUserService() {@Overridepublic void addUser(String username) {System.out.println("addUser:" + username);}@Overridepublic void deleteUser(int id) {System.out.println("删除用户ID:" + id);}@Overridepublic String getUser(int id) {System.out.println("获取用户，ID:" + id);return "代号: " + id;}};private void testProxy() {System.out.println("原来调用流程：");mUserService.addUser("小龙女");mUserService.getUser(9527);System.out.println("------------------------");// 下面动态代理，原有功能不变，加点日志class LoggingHandler implements InvocationHandler {private IUserService target;public LoggingHandler(IUserService target) {this.target = target;}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {System.out.println("begin to invoke method: " + method.getName());long start = System.currentTimeMillis();// 为了原有功能保持不变，所以这里调用原始方法（是否调用原始方法根据业务需要, 甚至可以修改结果，也可以啥都不处理）Object result = method.invoke(target, args);long duration = System.currentTimeMillis() - start;System.out.println("finish invoke method " + method.getName() + ", cost time: " + duration + "ms");return result;}}IUserService proxy = (IUserService) Proxy.newProxyInstance(IUserService.class.getClassLoader(),  new Class[]{IUserService.class}, new LoggingHandler(mUserService));// 模拟的一些实际业务场景，这里我通过反射把mUserService替换了。try {Field field = MyClass.class.getDeclaredField("mUserService");field.setAccessible(true);field.set(MyClass.this, proxy);} catch (Exception e) {e.printStackTrace();}System.out.println("使用动态代理后调用流程：");mUserService.addUser("小龙女");mUserService.getUser(9527);}   
}

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