Proxy Mode_Dynamic Proxy Implementation Class

1. Static proxy class

1.1 Define the interface

public interface A{
    void a(String str);
}

1.2 Implement the interface

public class B implements A{
    @Override
    public void a(String str) {
        System.out.println(str);
    }
}

1.3 Create a static proxy

public class Proxy {

    private B b;

    public Proxy(){

    }

    public Proxy(B b) {
        this.b= b;
    }
   

    public void a(String str){
        pre();
        b.a(str);
        after();
    }

    public void pre(){
        System.out.println("前执行");
    }
   
    public void contract(){
        System.out.println("后执行");
    }
}

1.4 Testing

public class Test{
    public static void main(String[] args) {
        B b= new B();
        Proxy proxy = new Proxy(b);
        proxy.a("我是传入参数");
    }
}

2. Dynamic proxy

2.1 Universal agent class

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * 万能代理类
 * @author administratoirs
 */
public class ProxyInvocationHandler implements InvocationHandler {
      //被代理的类
      private Object target;

    public void setObject(Object target) {
        this.target = target;
    }

    //生成得到代理类
    public Object getProxy(){
        //创建代理实例(通过反射获取参数)：类加载器、被代理的接口、InvocationHandler接口
        Object obj = Proxy.newProxyInstance(this.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
        return obj;
    }

    //执行代理实例，并返回结果
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        pre();
        Object res = method.invoke(target, args);
        after();
        return res;
    }

    public void pre() {
        System.out.println("执行前");
    }

    public void after(){
        System.out.println("执行后");
    }
}

2.2 Testing

public class Client {
    public static void main(String[] args) {
        //要被代理的类
        B b = new B();
        //代理角色：可通过ProxyInvocationHandler创建出来，可以通过这个类动态创建
        ProxyInvocationHandler handler = new ProxyInvocationHandler();
        //设置代理的真实角色
        handler.setObject(b);
        //getProxy动态生成代理类
        B proxy =(B) handler.getProxy();
        //就是执行invoke
        proxy.a("我是传入参数");
    }
}

Proxy Mode_Dynamic Proxy Implementation Class

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