动态代理

Java 动态代理详解
Java动态代理

使用

CGLIB

import org.springframework.cglib.proxy.*;

import java.lang.reflect.Method;

class Stu{
    void say(){
        System.out.println("I am a student");
    }
}
public class CGLibProxy {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Stu.class);
        enhancer.setCallback((MethodInterceptor) (Object o, Method method, Object[] objects, MethodProxy methodProxy) -> {
            System.out.println("cglib before");
            Object ret = methodProxy.invokeSuper(o,objects);
            System.out.println("cglib after");
            return ret;
        });
        Stu stu = (Stu) enhancer.create();
        stu.say();
        stu.toString();
    }
}

JDK动态代理

import lombok.AllArgsConstructor;

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

interface Person{
    void say();
    int eat();
}

class Student implements Person{
    @Override
    public void say() {
        System.out.println("我是学生");
    }

    @Override
    public int eat() {
        System.out.println("I eat 3");
        return 3;
    }
}
@AllArgsConstructor
class DynamicProxy implements InvocationHandler {
    private Person p;
    public Person getProxy(){
        return (Person) Proxy.newProxyInstance(p.getClass().getClassLoader(),p.getClass().getInterfaces(),this);
    }
    void before(){
        System.out.println("before");
    }
    void after(){
        System.out.println("after");
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
//        before();
        System.out.println("sout");
        Object ret = method.invoke(p,args);
        System.out.println("sout2");
//        after();
        return ret;
    }
}
public class TestDynamicProxy {
    public static void main(String[] args) {
        Person p = new Student();
        DynamicProxy dynamicProxy = new DynamicProxy(p);
        // (Person) Proxy.newProxyInstance(p.getClass().getClassLoader(),p.getClass().getInterfaces(),dynamicProxy);
        p = dynamicProxy.getProxy();
        p.say();
        p.eat();
    }

}

cglib

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;

/**
 * 被代理类
 */
class Suject {
    public void request() {
        System.out.println("被代理的类");
    }
    public void sayHello(){
        System.out.println("你好，你好，你好");
//        request();
    }
}
class SafetyCheckCallback implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("代理前。。。");
        Object result = methodProxy.invokeSuper(o, objects);
        System.out.println("代理后。。。");
        return result;
    }
}

public class CglibDynamicProxy {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Suject.class);
        enhancer.setCallback(new SafetyCheckCallback());
        Suject proxy = (Suject) enhancer.create();
        proxy.request();
        proxy.sayHello();
    }
}

jdk

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

/**
 * @ClassName: JdkDynamicProxy
 * @Description: TODO
 * @Create by: 
 * @Date: 2022/2/15 14:42
 */
interface IUpdatable {
    void update();
    void sayHello();
}

class UpdatableImpl implements IUpdatable {
    @Override
    public void update() {
        System.out.println("update UpdatableImpl.");
    }

    @Override
    public void sayHello() {
        System.out.println("你好，你好");
        update();
    }
}

/**
 * 代理类
 */
class SafetyInvocationHandler implements InvocationHandler {
    private Object target;

    public SafetyInvocationHandler(Object target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("代理前.");
        Object result = method.invoke(target, args);
        System.out.println("代理后.");
        return result;
    }
}
public class JdkDynamicProxy {
    public static void main(String[] args) {
        IUpdatable updatable = new UpdatableImpl();
        IUpdatable proxyUpdatable = (IUpdatable) Proxy.newProxyInstance(JdkDynamicProxy.class.getClassLoader(), new Class[]{IUpdatable.class}, new SafetyInvocationHandler(updatable));
        proxyUpdatable.update();
        proxyUpdatable.sayHello();
    }
}