动态代理练习以及万能动态代理模板

电玩女神 2022-08-29 05:41 126阅读 0赞

举例：房东、租客、中介

项目结构：  
![在这里插入图片描述][ef33aede773147d4ac26b6255e421908.PNG_pic_center]

静态代理模式：

Landlord

package demo01;
    
    public class Landlord implements Rent{ 
    
        public void rent(){ 
            System.out.println("房东要出租房子了！");
        }
    }

Rent:

package demo01;
    
    public interface Rent { 
    
        public void rent();
    }

Proxy；

package demo01;
    
    public class Proxy implements Rent{ 
        private Landlord landlord;
    
        public Proxy() { 
        }
    
        public Proxy(Landlord landlord) { 
            this.landlord = landlord;
        }
    
        @Override
        public void rent() { 
            seeHouse();
            landlord.rent();
        }
    
        public void seeHouse(){ 
            System.out.println("中介带你看房");
        }
    }

Tenants:

package demo01;
    
    public class Tenants { 
        public static void main(String[] args) { 
    
            Landlord landlord = new Landlord();
    
            Proxy proxy = new Proxy(landlord);
    
            proxy.rent();
        }
    }

动态代理：  
Landlord

package demo02;
    
    
    public class Landlord implements Rent{ 
    
        public void rent(){ 
            System.out.println("房东要出租房子了！");
        }
    }

Rent

package demo02;
    
    public interface Rent { 
    
        public void rent();
    }

ProxyInvocationHandler

package demo02;
    
    import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.Method;
    import java.lang.reflect.Proxy;
    
    public class ProxyInvocationHandler implements InvocationHandler { 
    
    
        private Rent rent;
    
        public void setRent(Rent rent){ 
            this.rent = rent;
        }
    
        public Object getProxy(){ 
            return Proxy.newProxyInstance(this.getClass().getClassLoader(),rent.getClass().getInterfaces(),this);
        }
    
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
    
            seeHouse();
            Object result = method.invoke(rent,args);
    
            return result;
        }
    
        public void seeHouse(){ 
            System.out.println("中介带看房子");
        }
    }

Tenants

package demo02;
    
    public class Tenants{ 
        public static void main(String[] args) { 
            Landlord landlord = new Landlord();
    
            ProxyInvocationHandler pih = new ProxyInvocationHandler();
    
            pih.setRent(landlord);
    
            Rent proxy = (Rent)pih.getProxy();
    
            proxy.rent();
        }
    }

可能到此你还没发现动态代理的好处，不着急，下面还有一个例子：

UserService:

public interface UserService { 
        public void add();
        public void delete();
        public void update();
        public void query();
    }

UserServiceImpl :

public class UserServiceImpl implements UserService{ 
        public void add() { 
            System.out.println("增加了一个用户！");
        }
    
        public void delete() { 
            System.out.println("删除了一个用户！");
        }
    
        public void update() { 
            System.out.println("修改了一个用户！");
        }
    
        public void query() { 
            System.out.println("查询了一个用户！");
        }
    }

ProxyInvocationHandler : (**敲黑板，重点**)

import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.Method;
    import java.lang.reflect.Proxy;
    
    //用这个类，自动生成代理类
    public class ProxyInvocationHandler implements InvocationHandler { 
    
        //被代理的接口
        private Object target;
    
        public void setTarget(Object target) { 
            this.target = target;
        }
    
        //生成得到的代理类
        public Object getProxy(){ 
            return Proxy.newProxyInstance(this.getClass().getClassLoader(),target.getClass().getInterfaces(),this);
        }
    
        //处理代理实例，并返回结果
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
            log(method.getName());
            Object result = method.invoke(target,args);
    
            return result;
        }
    
        public void log(String msg){ 
            System.out.println("执行了"+msg+"方法");
        }
    
    }

Client ：

public class Client { 
    
        public static void main(String[] args) { 
    
            //真实角色
            UserServiceImpl userService = new UserServiceImpl();
    
            //代理角色，不存在
            ProxyInvocationHandler pih = new ProxyInvocationHandler();
    
            //设置需要代理的对象
            pih.setTarget(userService);
    
            //动态生成代理类
            UserService proxy = (UserService)pih.getProxy();
            
            proxy.add();
    
        }
    
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5NjM1Mw_size_16_color_FFFFFF_t_70_pic_center]  
最后附上万能的动态代理模板：

import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.Method;
    import java.lang.reflect.Proxy;
    
    //用这个类，自动生成代理类
    public class ProxyInvocationHandler implements InvocationHandler { 
    
        //被代理的接口
        private Object target;
    
        public void setTarget(Object target) { 
            this.target = target;
        }
    
        //生成得到的代理类
        public Object getProxy(){ 
            return Proxy.newProxyInstance(this.getClass().getClassLoader(),target.getClass().getInterfaces(),this);
        }
    
        //处理代理实例，并返回结果
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
           
            Object result = method.invoke(target,args);
    
            return result;
        }
    
    }

[ef33aede773147d4ac26b6255e421908.PNG_pic_center]: /images/20220829/85d78f704268498f9ca3273c94dd6b20.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5NjM1Mw_size_16_color_FFFFFF_t_70_pic_center]: /images/20220829/a5a5ec799e774fbe8e6396aa1997ebab.png