java面试常见模式问题---代理模式

// 抽象角色：租房
public interface Rent {
   public void rent();
}

// 真实角色: 房东，房东要出租房子
public class Host implements Rent{
   public void rent() {
       System.out.println("房屋出租");
  }
}

//代理角色：中介
public class Proxy implements Rent {
   private Host host;
   public Proxy() { }
   public Proxy(Host host) {
       this.host = host;
  }
   // 租房
   public void rent(){
       seeHouse();
       host.rent();
       fare();
  }
   // 看房
   public void seeHouse(){
       System.out.println("带房客看房");
  }
   // 收中介费
   public void fare(){
       System.out.println("收中介费");
  }
}

// 客户类，一般客户都会去找代理！
public class Client {
   public static void main(String[] args) {
       // 房东要租房
       Host host = new Host();
       // 中介帮助房东
       Proxy proxy = new Proxy(host);
       // 你去找中介！
       proxy.rent();
  }
}

public interface UserService {
    
    void login();
    
    void loGout();
}

public class UserServiceImpl implements UserService{
    @Override
    public void login() {
        System.out.println("用户登录...");
    }
    @Override
    public void logout() {
        System.out.println("用户推出登录...");
    }
}

public class JDKProxyFactory implements InvocationHandler {
    // 目标对象(被代理对象)
    private Object target;
    public JDKProxyFactory(Object target) {
        super();
        this.target = target;
    }
    
    public Object createProxy() {
        // 1.得到目标对象的类加载器
        ClassLoader classLoader = target.getClass().getClassLoader();
        // 2.得到目标对象的实现接口
        Class<?>[] interfaces = target.getClass().getInterfaces();
        // 3.第三个参数需要一个实现invocationHandler接口的对象
        Object newProxyInstance = Proxy.newProxyInstance(classLoader, interfaces, this);
        return newProxyInstance;
    }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("JDK 动态代理：登录/登出前逻辑校验......");
        Object invoke = method.invoke(target, args);
        System.out.println("JDK 动态代理：登录/登出后日志打印......");
        return invoke;
    }
    public static void main(String[] args) {
        // 1.创建对象
        UserServiceImpl userService = new UserServiceImpl();
        // 2.创建代理对象
        JDKProxyFactory jdkProxyFactory = new JDKProxyFactory(userService);
        // 3.调用代理对象的增强方法,得到增强后的对象
        UserService userServiceProxy = (UserService) jdkProxyFactory.createProxy();
        userServiceProxy.login();
        System.out.println("==================================");
        userServiceProxy.logout();
    }
}

public class CglibProxyFactory implements MethodInterceptor {
    // 目标对象(被代理对象)
    private Object target;
    // 使用构造方法传递目标对象
    public CglibProxyFactory(Object target) {
        super();
        this.target = target;
    }
    
    public Object createProxy() {
        // 1.创建Enhancer
        Enhancer enhancer = new Enhancer();
        // 2.传递目标对象的class
        enhancer.setSuperclass(target.getClass());
        // 3.设置回调操作
        enhancer.setCallback(this);
        return enhancer.create();
    }
    
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("cglib 动态代理：登录/登出前逻辑校验......");
        Object invoke = method.invoke(target, objects);
        System.out.println("cglib 动态代理：登录/登出后日志打印......");
        return invoke;
    }
    public static void main(String[] args) {
        // 1.创建对象
        UserServiceImpl userService = new UserServiceImpl();
        // 2.创建代理对象
        CglibProxyFactory cglibProxyFactory = new CglibProxyFactory(userService);
        // 3.调用代理对象的增强方法,得到增强后的对象
        UserService userServiceProxy = (UserService) cglibProxyFactory.createProxy();
        userServiceProxy.login();
        System.out.println("==================================");
        userServiceProxy.logout();
    }
}