代理模式

男娘i 2021-09-21 00:48 283阅读 0赞

**1.静态代理**

public interface Company { 
        void cooperation();
    }

public class Start implements Company { 
    
        public void cooperation() { 
            System.out.println("1");
        }
    }

代理类

public class Agent implements Company { 
    
        private Company company;
    
        public Agent(Company company) { 
            this.company = company;
        }
    
        public void cooperation() { 
            System.out.println("===before===");
            company.cooperation();
            System.out.println("===after===");
        }
    }

调用

Company company=new Start();
    Agent agent=new Agent(company);
    agent.cooperation();

**2.动态代理 jdk实现**

public class JdkProxy implements InvocationHandler { 
    
        private Company company;
    
        public JdkProxy(Company company) { 
            this.company = company;
        }
    
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
            System.out.println("=====before=====");
            Object result= method.invoke(company,args);
            System.out.println("=====after=====");
            return result;
        }
    }

调用

动态生成代理对象需要调用JDK中的java.lang.reflect.Proxy类的newProxyInstance方法，这个方法需要三个参数：  
@CallerSensitive  
public static Object newProxyInstance(ClassLoader loader,\]Class<?>\[\] interfaces,InvocationHandler h)  
ClassLoader loader：类加载器，用来加载目标对象类，因为是在运行时获得目标对象，所以肯定需要用到反射。  
Class<?>\[\] interfaces：目标对象类实现的接口集合，这些接口中定义目标对象可以执行的方法。  
InvocationHandler h：这个参数代表的是动态代理对象在调用方法的时候,会将方法转发到哪一个invocationHandler对象身上，InvocationHandler是个接口，  
需要自己实现它，然后定义自己的动态代理执行方法。  
创建包含动态代理对象具体执行方法的实现类。

Company company = new Start();
    JdkProxy jdkProxy = new JdkProxy(company);
    Company proxy = (Company) Proxy.newProxyInstance(jdkProxy.getClass().getClassLoader(), company.getClass().getInterfaces(), jdkProxy);
    proxy.cooperation();

3.cglib 动态代理

public class AloneStart { 
        /** 合作 */
        public void cooperation() { 
            System.out.println("is show time");
        }
    }

代理类

package com.jd.xq.proxy;
    
    
    import org.springframework.cglib.proxy.MethodInterceptor;
    import org.springframework.cglib.proxy.MethodProxy;
    
    import java.lang.reflect.Method;
    
    /** * @author duanxiaoqiu * @Date 2019-12-18 14:44 **/
    public class CglibProxy implements MethodInterceptor { 
    
        public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { 
            System.out.println("=====before====");
            Object result = methodProxy.invokeSuper(o, objects);
            System.out.println("=====after====");
            return result;
        }
    }

Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(AloneStart.class);
    enhancer.setCallback(new CglibProxy());
    
    AloneStart aloneStart = (AloneStart) enhancer.create();
    aloneStart.cooperation();

spring aop等