JDK动态代理

• .利用了JDK API，动态地在内存中构建代理对象，从而实现对目标对象的代理功能。
• .动态代理是在运行时动态生成的，即编译完成后没有实际的class文件，而是在运行时动态生成类字节码，并加载到JVM中
• .不需要实现接口（指的是被代理类的接口），但是要求目标对象必须实现接口，否则不能使用动态代理
• .需要实现InvocationHandler接口，并实现invoke方法，在该方法里面实现增强效果，该方法有三个参数，在下面进行详解
• .代理类调用是通过Proxy的newProxyInstance的方法进行生成
• .使用泛型可以代理多个接口

import lombok.Data;

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




public class JDKTest {
    public static void main(String[] args) {
        UserHandle userHandle = new UserHandle(new User("xiaoxu",22,"男"));
        //通过这个方法获取代理对象
        People people = userHandle.PeopleProxy();
        //通过代理对象调用方法
        people.run(20.1);
        people.eat();

        //使用泛型
        Proxy1 peopleProxy1= new Proxy1<>(new User("daxu",23,"男"));
        People people1 = peopleProxy1.GetProxy();
        people1.run(21.1);
    }
}

//代理的接口
interface People{
    void run(Double velocity);
    void eat();
}

//实现类
@Data
class User implements People{
    private String name;
    private Integer age;
    private String sex;

    User(String name,Integer age,String sex){
        this.name = name;
        this.age = age;
        this.sex = sex;
    }
    public void run(Double velocity){
        System.out.println(name+"正以"+velocity+"的速度再跑");
    }

    @Override
    public void eat() {
        System.out.println(name+"吃大餐");
    }
}

class UserHandle implements InvocationHandler{

    private final People people;

    UserHandle(People people){
        this.people = people;
    }

    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        start();
        Object invoke = method.invoke(people, args);
        end();
        return invoke;//此处放回的就是方法实际的放回值
    }

    void start(){
        System.out.println("-----开始了-------");
    }

    void end(){
        System.out.println("-------结束了-----");
    }

    People PeopleProxy(){
        //获取加载器
        ClassLoader classLoader = User.class.getClassLoader();
        //获取类接口
        Class[] interfaces = User.class.getInterfaces();
        
        return (People) Proxy.newProxyInstance(classLoader, interfaces,this);
    }
}

class Proxy1 implements InvocationHandler{

    private final T people;

    Proxy1(T people){
        this.people = people;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        start();
        Object invoke = method.invoke(people, args);
        end();
        return invoke;
    }

    void start(){
        System.out.println("-----开始了-------");
    }

    void end(){
        System.out.println("-------结束了-----");
    }

    T GetProxy(){
        ClassLoader classLoader = User.class.getClassLoader();
        Class[] interfaces = User.class.getInterfaces();
        return (T) Proxy.newProxyInstance(classLoader, interfaces,this);
    }
}