造作ai助手深度解析Java动态代理：JDK与CGLIB原理对比与面试要点 2026-04-08

// 业务接口
public interface UserService {
    void saveUser(String username);
}

// 真实业务类
public class UserServiceImpl implements UserService {
    @Override
    public void saveUser(String username) {
        System.out.println("正在保存用户：" + username);
    }
}

// 静态代理类
public class UserServiceProxy implements UserService {
    private UserService target;
    
    public UserServiceProxy(UserService target) {
        this.target = target;
    }
    
    @Override
    public void saveUser(String username) {
        System.out.println("【日志】开始保存用户：" + username);
        System.out.println("【权限】校验用户权限...");
        target.saveUser(username);
        System.out.println("【日志】用户保存完成");
    }
}

// 1. 定义业务接口
public interface UserService {
    void saveUser(String username);
    String getUser(String username);
}

// 2. 目标类实现接口
public class UserServiceImpl implements UserService {
    @Override
    public void saveUser(String username) {
        System.out.println("执行保存：" + username);
    }
    @Override
    public String getUser(String username) {
        return "用户：" + username;
    }
}

// 3. 自定义InvocationHandler
public class LogInvocationHandler implements InvocationHandler {
    private Object target;  // 持有目标对象
    
    public LogInvocationHandler(Object target) {
        this.target = target;
    }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("【日志】开始执行方法：" + method.getName());
        long start = System.currentTimeMillis();
        Object result = method.invoke(target, args);  // 反射调用目标方法
        System.out.println("【日志】执行完成，耗时：" + (System.currentTimeMillis() - start) + "ms");
        return result;
    }
}

// 4. 使用代理
public class Main {
    public static void main(String[] args) {
        UserService target = new UserServiceImpl();
        UserService proxy = (UserService) Proxy.newProxyInstance(
            target.getClass().getClassLoader(),
            target.getClass().getInterfaces(),
            new LogInvocationHandler(target)
        );
        proxy.saveUser("张三");
    }
}

// 1. 目标类（无需接口）
public class OrderService {
    public void createOrder(String orderId) {
        System.out.println("创建订单：" + orderId);
    }
}

// 2. 自定义MethodInterceptor
public class LogMethodInterceptor implements MethodInterceptor {
    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("【日志】CGLIB代理开始执行：" + method.getName());
        long start = System.currentTimeMillis();
        Object result = proxy.invokeSuper(obj, args);  // 调用父类（目标类）方法
        System.out.println("【日志】执行完成，耗时：" + (System.currentTimeMillis() - start) + "ms");
        return result;
    }
}

// 3. 使用代理
public class Main {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(OrderService.class);          // 设置目标类为父类
        enhancer.setCallback(new LogMethodInterceptor());    // 设置回调拦截器
        OrderService proxy = (OrderService) enhancer.create(); // 生成代理子类
        proxy.createOrder("ORD-001");
    }
}