my助手ai深度拆解：一文吃透Java代理模式（2026.04.09）

public class TaskService {

    public void dealTask(String taskName) {
        long startTime = System.currentTimeMillis();   // 统计逻辑
        System.out.println("执行任务：" + taskName);     // 核心业务
        long cost = System.currentTimeMillis() - startTime; // 统计逻辑
        System.out.println("耗时：" + cost + "ms");
    }
}

// 1. 抽象接口
public interface UserService {
    void addUser(String username);
    void deleteUser(String username);
}

// 2. 目标类：专注核心业务
public class UserServiceImpl implements UserService {
    @Override
    public void addUser(String username) {
        System.out.println("数据库新增用户：" + username);
    }
    @Override
    public void deleteUser(String username) {
        System.out.println("数据库删除用户：" + username);
    }
}

// 3. 静态代理类：手动编写，附加日志功能
public class UserServiceProxy implements UserService {
    private final UserService target;
    public UserServiceProxy(UserService target) { this.target = target; }
    
    @Override
    public void addUser(String username) {
        System.out.println("日志：开始执行addUser，参数：" + username); // 前置增强
        target.addUser(username);
        System.out.println("日志：addUser执行完毕");                     // 后置增强
    }
    
    @Override
    public void deleteUser(String username) {
        System.out.println("日志：开始执行deleteUser，参数：" + username);
        target.deleteUser(username);
        System.out.println("日志：deleteUser执行完毕");
    }
}

// 1. 业务接口（必须！JDK动态代理要求目标类实现接口）
public interface UserService {
    void addUser(String username);
}

public class UserServiceImpl implements UserService {
    @Override
    public void addUser(String username) {
        System.out.println("新增用户：" + username);
    }
}

// 2. 实现InvocationHandler，定义增强逻辑
public class LogInvocationHandler implements InvocationHandler {
    private final Object target;
    public LogInvocationHandler(Object target) { this.target = target; }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("日志：" + method.getName() + "方法开始执行");  // 前置增强
        Object result = method.invoke(target, args);                      // 反射调用
        System.out.println("日志：" + method.getName() + "方法执行结束");  // 后置增强
        return result;
    }
}

// 3. 动态生成代理对象
UserService target = new UserServiceImpl();
UserService proxy = (UserService) Proxy.newProxyInstance(
    target.getClass().getClassLoader(),
    target.getClass().getInterfaces(),
    new LogInvocationHandler(target)
);
proxy.addUser("张三");

// 1. 目标类：普通类，无需实现接口
public class UserService {
    public void addUser(String username) {
        System.out.println("新增用户：" + username);
    }
}

// 2. 实现MethodInterceptor，定义增强逻辑
public class LogMethodInterceptor implements MethodInterceptor {
    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) 
            throws Throwable {
        System.out.println("日志：" + method.getName() + "开始执行");
        Object result = proxy.invokeSuper(obj, args);  // 调用父类原始方法
        System.out.println("日志：" + method.getName() + "执行结束");
        return result;
    }
}

// 3. 通过Enhancer生成代理对象
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(UserService.class);
enhancer.setCallback(new LogMethodInterceptor());
UserService proxy = (UserService) enhancer.create();
proxy.addUser("张三");