不懂Nacos没关系，可以看看它是怎么运用代理模式的

public interface ClientOperationService {
    
    /**
     * Register instance to service.
     *
     */
    void registerInstance(Service service, Instance instance, String clientId) throws NacosException;
    
    // ...
}

@Component("ephemeralClientOperationService")
public class EphemeralClientOperationServiceImpl implements ClientOperationService {
    
    @Override
    public void registerInstance(Service service, Instance instance, String clientId) throws NacosException {
       // ... 临时实例注册逻辑实现
    }
    // ...
}

@Component("persistentClientOperationServiceImpl")
public class PersistentClientOperationServiceImpl extends RequestProcessor4CP implements ClientOperationService {
    
    @Override
    public void registerInstance(Service service, Instance instance, String clientId) {
       // ... 永久实例注册逻辑实现
    }
    // ...
}    

@Component
public class ClientOperationServiceProxy implements ClientOperationService {
    
    private final ClientOperationService ephemeralClientOperationService;
    
    private final ClientOperationService persistentClientOperationService;
    
    public ClientOperationServiceProxy(EphemeralClientOperationServiceImpl ephemeralClientOperationService,
            PersistentClientOperationServiceImpl persistentClientOperationService) {
        this.ephemeralClientOperationService = ephemeralClientOperationService;
        this.persistentClientOperationService = persistentClientOperationService;
    }
    
    @Override
    public void registerInstance(Service service, Instance instance, String clientId) throws NacosException {
        final ClientOperationService operationService = chooseClientOperationService(instance);
        operationService.registerInstance(service, instance, clientId);
    }
    
    private ClientOperationService chooseClientOperationService(final Instance instance) {
        return instance.isEphemeral() ? ephemeralClientOperationService : persistentClientOperationService;
    }
    // ...
}

public interface UserService {
 void login(String username, String password);
}

public class UserServiceImpl implements UserService{

 @Override
 public void login(String username, String password) {
  System.out.println("User Login Service!");
 }
}

public class LogHandler implements InvocationHandler {

 /**
  * 被代理的对象，实际的方法执行者
  */
 Object target;

 public LogHandler(Object object) {
  this.target = object;
 }


 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
  System.out.println("Before Login---");
  // 调用target的method方法
  Object result = method.invoke(target, args);
  System.out.println("After Login---");
  return result;
 }
}

public class JdkProxyTest {

   public static void main(String[] args) {

      // 创建被代理的对象，UserService接口的实现类
      UserServiceImpl userService = new UserServiceImpl();

      // 创建代理对象，包含三个参数：ClassLoader、目标类实现接口数组、事件处理器
      UserService userProxy = (UserService) Proxy.newProxyInstance(userService.getClass().getClassLoader(),
            userService.getClass().getInterfaces(),
            new LogHandler(userService));

      userProxy.login("admin", "123456");
   }
}

Before Login---
User Login Service!
After Login---

public class ProxyUtils {

   /**
    * 将根据类信息动态生成的二进制字节码保存到硬盘中，默认的是clazz目录下
    * params: clazz 需要生成动态代理类的类
    * proxyName: 为动态生成的代理类的名称
    */
   public static void generateClassFile(Class clazz, String proxyName) {
      // 根据类信息和提供的代理类名称，生成字节码
      byte[] classFile = ProxyGenerator.generateProxyClass(proxyName, clazz.getInterfaces());
      String paths = clazz.getResource(".").getPath();
      System.out.println(paths);

      try (FileOutputStream out = new FileOutputStream(paths + proxyName + ".class")) {
         //保留到硬盘中
         out.write(classFile);
         out.flush();
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

public class JdkProxyTest {

 public static void main(String[] args) {

  // 创建被代理的对象，UserService接口的实现类
  UserServiceImpl userService = new UserServiceImpl();

  // 创建代理对象，包含三个参数：ClassLoader、目标类实现接口数组、事件处理器
  UserService userProxy = (UserService) Proxy.newProxyInstance(userService.getClass().getClassLoader(),
    userService.getClass().getInterfaces(),
    new LogHandler(userService));

  userProxy.login("admin", "123456");

  // 保存JDK动态代理生成的代理类，类名保存为 UserServiceProxy
  ProxyUtils.generateClassFile(userService.getClass(), "UserServiceProxy");

 }
}

public final class UserServiceProxy extends Proxy implements UserService {
    private static Method m1;
    private static Method m2;
    private static Method m3;
    private static Method m0;

    public UserServiceProxy(InvocationHandler var1) throws  {
        super(var1);
    }

    public final boolean equals(Object var1) throws  {
        try {
            return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final void login(String var1, String var2) throws  {
        try {
            super.h.invoke(this, m3, new Object[]{var1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    public final int hashCode() throws  {
        try {
            return (Integer)super.h.invoke(this, m0, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m3 = Class.forName("com.secbro2.proxy.UserService").getMethod("login", Class.forName("java.lang.String"), Class.forName("java.lang.String"));
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

<dependency>
     <groupId>cglib</groupId>
     <artifactId>cglib</artifactId>
     <version>3.1</version>
</dependency>

public class OrderService {
 public void order(String orderNo){
  System.out.println("order something... ");
 }
}

/**
 * 动态代理类，实现方法拦截器接口
 **/
public class LogInterceptor implements MethodInterceptor {

 /**
  * 给目标对象创建一个代理对象
  */
 public Object getProxyInstance(Class targetClass){
  // 1.工具类
  Enhancer enhancer = new Enhancer();
  // 2.设置父类
  enhancer.setSuperclass(targetClass);
  // 3.设置回调函数
  enhancer.setCallback(this);
  // 4.创建子类（代理对象）
  return enhancer.create();
  // 上述方法也可以直接使用如下代码替代
  // return Enhancer.create(targetClass,this);
 }

 /**
  *
  * @param o 要进行增强的对象
  * @param method 拦截的方法
  * @param objects 方法参数列表（数组）
  * @param methodProxy 方法的代理，invokeSuper方法表示对被代理对象方法的调用
  */
 @Override
 public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
  // 扩展日志记录
  System.out.println("LogInterceptor：Before Login---");
  // 注意：调用的invokeSuper而不是invoke，否则死循环。
  // methodProxy.invokeSuper执行的是原始类的方法，method.invoke执行的是子类的方法
  Object object = methodProxy.invokeSuper(o, objects);
  // 扩展日志记录
  System.out.println("LogInterceptor：After Login---");
  return object;
 }
}

public class CglibTest {

 public static void main(String[] args) {
  OrderService orderService = (OrderService) new LogInterceptor().getProxyInstance(OrderService.class);
  orderService.order("123");
 }
}

LogInterceptor：Before Login---
order something... 
LogInterceptor：After Login---

// 基于JDK的动态代理实现类
org.springframework.aop.framework.JdkDynamicAopProxy
// 基于Cglib的动态代理实现类
org.springframework.aop.framework.CglibAopProxy