静态代理与动态代理（jdk,cglib)

举个例子，我们租房可以自己找房源，也可以找中介，中介就相当于代理。
静态代理
(1)租房接口IRentingHouse

public interface IRentingHouse {
    void renting();
}

(2)租房接口实现类RentingHouseImpl

//自己找房源
public class RentingHouseImpl implements IRentingHouse{
    @Override
    public void renting() {
        System.out.println("我要租房");
    }
}

(3)中介代理类，他也需要找房子所以也需要实现IRentingHouse这个接口，代理类中需要声明当前接口的属性

public class RentingHouseProxy implements IRentingHouse {
    private IRentingHouse rentingHouse;

    public RentingHouseProxy(IRentingHouse rentingHouse) {
        this.rentingHouse = rentingHouse;
    }

    @Override
    public void renting() {
        System.out.println("中介找房源");
        rentingHouse.renting();
        System.out.println("签订合同，交服务费");
    }
}

(4)测试类Test

public class Test {

    public static void main(String[] args) {
        IRentingHouse rentingHouse = new RentingHouseImpl();
        RentingHouseProxy rentingHouseProxy = new RentingHouseProxy(rentingHouse);
        rentingHouseProxy.renting();
    }
}

执行结果

中介找房源
我要租房
签订合同，交服务费

静态代理: 需要对每个业务都写一个代理类，比较冗余，这就是它与动态代理的区别。
动态代理
动态代理分为jdk动态代理和cglib动态代理，简单讲下区别:
    JDK动态代理只能对实现了接口的类生成代理,而不能针对类;
    CGLIB是针对类实现代理,主要是对指定的类生成一个子类,覆盖其中的方法(继承);

下面分别用jdk动态代理和cglib动态代理来实现这个需求吧
jdk动态代理
IRentingHouse接口和实现类RentingHouseImpl还是老样子，贴一下代码

public interface IRentingHouse {
    void renting();
}

//自己找房源
public class RentingHouseImpl implements IRentingHouse{
    @Override
    public void renting() {
        System.out.println("我要租房");
    }
}

代理工厂类，生成代理对象

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

/**
 * 代理工厂类-饿汉
 */
public class ProxyFactory {

    private ProxyFactory() {
    }

    private static ProxyFactory proxyFactory = new ProxyFactory();

    public static ProxyFactory getInstance() {
        return proxyFactory;
    }

    public Object getJdkProxy(Object obj) {
        return Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Object result = null;
                System.out.println("中介找房源");
                result = method.invoke(obj, args);
                System.out.println("签订合同，交服务费");
                return result;
            }
        });
    }
}

测试类Test

public class Test {
    public static void main(String[] args) {
        IRentingHouse rentingHouse = new RentingHouseImpl();
        IRentingHouse jdkProxy = (IRentingHouse) ProxyFactory.getInstance().getJdkProxy(rentingHouse);
        jdkProxy.renting();
    }
}

执行结果

中介找房源
我要租房
签订合同，交服务费

cglib动态代理
首先pom.xml中添加依赖

<dependency>
	<groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>2.1_2</version>
</dependency>

ProxyFactory中新加方法

public Object getCglibProxy(Object obj) {
        return Enhancer.create(obj.getClass(), new MethodInterceptor() {
            @Override
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                Object result = null;
                System.out.println("中介找房源");
                result = method.invoke(obj, objects);
                System.out.println("签订合同，交服务费");
                return result;
            }
        });
    }

测试类

public class Test {
    public static void main(String[] args) {
        RentingHouseImpl rentingHouse1 = new RentingHouseImpl();
        RentingHouseImpl cglibProxy = (RentingHouseImpl) ProxyFactory.getInstance().getCglibProxy(rentingHouse1);
        cglibProxy.renting();
    }
}

本文地址：https://blog.csdn.net/weixin_32896095/article/details/110233562