java代理模式（笔记）

一、静态代理
条件：需要目标对象和代理对象实现相同的接口

package com.bycotrun.proxy;

//代理接口类
public interface ProxyInterface {
	public String show(String name);
}

package com.bycotrun.proxy;

//代理目标类
public class ProxyImpl implements ProxyInterface {

	@Override
	public String show(String name) {
		System.out.println("目标代理类" + name);
		return name;
	}
}

package com.bycotrun.proxy;

//静态代理类
public class StaticPorxy implements ProxyInterface {

	private ProxyInterface por = new ProxyImpl();

	@Override
	public String show(String name) {
		System.out.println("前置增强");
		return por.show(name);
	}
}

package com.bycotrun.proxy;

//测试
public class Test {
	public static void main(String[] args) {
		StaticPorxy por = new StaticPorxy();
		por.show("xiaom");
	}
}

二、jdk动态代理
条件：需要目标对象和代理对象实现相同的接口

原理：用户调用代理对象的show()方法，代理对象会通过反射调用InvocationHandler对象的invoke()方法，invoke方法在通过反射调用目标对象的show()方法。

package com.bycotrun.proxy;

//jdk动态代理接口类
public interface ProxyInterface {
	public String show(String name);
}

package com.bycotrun.proxy;

//jdk动态代理目标类
public class ProxyImpl implements ProxyInterface {

	@Override
	public String show(String name) {
		System.out.println("jdk动态代理目标代理类" + name);
		return name;
	}

}

package com.bycotrun.proxy;

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

//jdk动态代理类
public class JdkPorxyFactory {
	private ProxyInterface por = new ProxyImpl();

	public ProxyInterface getPorxy() {
		return (ProxyInterface) Proxy.newProxyInstance(por.getClass().getClassLoader(), por.getClass().getInterfaces(),
				new InvocationHandler() {
					@Override
					public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
						System.out.println("jdk动态代理前置");
						Object invoke = method.invoke(por, args);
						return invoke;
					}
				});
	}
}

package com.bycotrun.proxy;

//测试
public class Test {
	public static void main(String[] args) {
		
		JdkPorxyFactory por = new JdkPorxyFactory();
		ProxyInterface porxy = por.getPorxy();
		String show = porxy.show("xiaom");
		System.out.println(show);
	
	}
}

三、cglib动态代理

package com.bycotrun.proxy;

//cglib动态代理目标类
public class ProxyTarget {

	public String show(String name) {
		System.out.println("cglib动态代理目标代理类" + name);
		return name;
	}

}

package com.bycotrun.proxy;

import java.lang.reflect.Method;

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

//cglib动态代理类
public class CglibProxyFactorry implements MethodInterceptor {
	ProxyTarget pro = new ProxyTarget();

	public ProxyTarget getProxy() {
		Enhancer enhancer = new Enhancer();
		// 目标代理类
		enhancer.setSuperclass(ProxyTarget.class);
		// 回调方法
		enhancer.setCallback(this);
		// 代理类
		ProxyTarget proxy = (ProxyTarget) enhancer.create();
		return proxy;
	}

	@Override
	public Object intercept(Object arg0, Method arg1, Object[] arg2, MethodProxy arg3) throws Throwable {
		System.out.println("cglib动态代理前置");
		Object invoke = arg1.invoke(pro, arg2);
		return invoke;
	}

}

package com.bycotrun.proxy;

//测试
public class Test {
	public static void main(String[] args) {
		
		CglibProxyFactorry cglibFactorry = new CglibProxyFactorry();
		ProxyTarget proxy = cglibFactorry.getProxy();
		String show = proxy.show("xiaom");
		System.out.println(show);

	}
}

四、动态代理类选择
1、目标对象有接口实现使用jdk动态代理，没有只能用cglib动态代理
2、jdk8以下cglib效率优于jdk动态代理。