Java两种方式实现动态代理

@CallerSensitive
public static Object newProxyInstance(ClassLoader loader,
                   Class<?>[] interfaces,
                   InvocationHandler h)
  throws IllegalArgumentException
{
//...
}

public interface UserService {
  void eat();
}

public class UserServiceImpl implements UserService {
  @Override
  public void eat() {
    System.out.println("吃东西");
  }
}

public class MyAspect {
  /**
   * 前置通知
   */
  public void before() {
    System.out.print("先洗手再");
  }
}

/**
 * 产生代理对象的工厂类
 */
public class MyFactoryBean {

  private MyFactoryBean() {
  }
  
  public static UserService getInstance() {
    // target ： 目标类
    final UserService userService = new UserServiceImpl();
    // Aspect : 切面类
    final MyAspect myAspect = new MyAspect();
    // Weaving : 织入，也就是产生代理的过程
    UserService proxyInstance = (UserService) Proxy.newProxyInstance(UserService.class.getClassLoader(),
        new Class[]{UserService.class}, (Object proxy, Method method, Object[] args) -> {
          // 模拟切点 - pointcut
          if ("eat".equals(method.getName())) {
            myAspect.before();
          }
          return method.invoke(userService, args);
        });
    return proxyInstance;
  }
}

  public static void main(String[] args) {
    UserService userService = MyFactoryBean.getInstance();
    // 先洗手再吃东西
    userService.eat();
  }

/**
 * 产生代理对象的工厂类
 */
public class MyFactoryBean {

  private MyFactoryBean() {
  }

  public static UserService getInstance() {
    // target ： 目标类
    final UserService userService = new UserServiceImpl();
    // Aspect : 切面类
    final MyAspect myAspect = new MyAspect();
    // Weaving : 织入，也就是产生代理的过程
    Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(userService.getClass());
    enhancer.setUseCache(false);
    enhancer.setCallback(new MethodInterceptor() {
      @Override
      public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        // 模拟 pointcut-切点
        if ("eat".equals(method.getName())) {
          myAspect.before();
        }
        return methodProxy.invokeSuper(o, objects);
      }
    });
    return (UserService) enhancer.create();
  }

  public static void main(String[] args) {
    UserService proxyInstance = MyFactoryBean.getInstance();
    // 先洗手再吃东西
    proxyInstance.eat();
  }
}