java代理与动态代理的学习

静态代理比较简单，就是代理对象与被代理对象继承相同的接口，代理类负责调用被代理类（委托类）的对象的相关方法去提供具体的服务，一个代理类只能为一个接口服务，要是有很多服务的话需要开很多代理类。而动态代理则是由反射实现，可以用一个代理类实现所有的代理功能，这点是比较方便的。

先看看静态代理：

一个接口类，若干个接口实现类和一个代理类即可

接口

package proxy;

public interface Women {
    public void eat();
    public void play();

}

接口实现类一

package proxy;

public class Lily implements Women{

    @Override
    public void eat() {
        System.out.println("i'm Lily,i love eat banana");
    }

    @Override
    public void play() {
        System.out.println("i'm Lily,i love swimming");
    }

}

接口实现类二

package proxy;

public class Juli implements Women{

    @Override
    public void eat() {
        System.out.println("i'm Juli,i love eat banana");
    }

    @Override
    public void play() {
        System.out.println("i'm Juli,i love swimming");
    }

}

代理类

package proxy;

public class Proxy implements Women{
	private Women women;
	public Proxy(){
		this.women=new Lily();//设一个代理的默认值
	}
	public  Proxy(Women women){
		this.women=women;
	}
	@Override
	public void eat() {
		this.women.eat();
	}
	@Override
	public void play() {
		this.women.play();
	}

}

测试

package proxy;

public class StaticProxyTest {
	public static void main(String[] args) {
		Proxy p;
		p=new Proxy();
		p.eat();
		p.play();
		p=new Proxy(new Juli());
		p.eat();
		p.play();
	}

}

测试结果　

i'm Lily,i love eat banana
i'm Lily,i love swimming
i'm Juli,i love eat banana
i'm Juli,i love swimming

动态代理的话主要有两种实现方式，一种是jdk动态代理实现，一种是cglib代理。JDK动态代理只能针对实现了接口的类生成代理，CGLIB（CODE GENERLIZE LIBRARY）代理是针对类实现代理，

主要是对指定的类生成一个子类，覆盖其中的所有方法，所以该类或方法不能声明称final的。

先看看jdk代理

代理类

package proxy;

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

public class JdkProxy implements InvocationHandler{
	private Women women;
	public JdkProxy(Women women){
		this.women=women;
	}
	public static Women newProxyInstance(Women women){
		return (Women) Proxy.newProxyInstance(JdkProxy.class.getClassLoader(), new Class<?>[] { Women.class }, new JdkProxy(women));

	}

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

}

改成通用点的

package proxy;

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

public class JdkProxy implements InvocationHandler{

	private  Object obj;
	public JdkProxy(Object obj){
		this.obj=obj;
	}
	public static Object newProxyInstance(Object targetObject){//传入的是类的实现接口
		return Proxy.newProxyInstance(JdkProxy.class.getClassLoader(), targetObject.getClass().getInterfaces(),new JdkProxy(targetObject));

	}

	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		return method.invoke(this.obj, args);
	}

}

　　

测试类　

package proxy;

public class JdkProxyTest {
	public static void main(String[] args) {
		Women women= JdkProxy.newProxyInstance(new Lily());
		women.eat();
		women.play();
	}

}　

 

测试结果

i'm Lily,i love eat banana
i'm Lily,i love swimming

　　

Cglib代理类

package proxy;

import java.lang.reflect.Method;

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

public class CglibProxy implements MethodInterceptor {
	private CglibProxy() {
	}
	public static <T extends Women> Women newProxyInstance(Class<T> targetInstanceClazz){
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(targetInstanceClazz);
        enhancer.setCallback(new CglibProxy());
        return (Women) enhancer.create();//返回的对象是一个封装了"实现类"的代理类，是实现类的实例

    }

	@Override
	public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
		return proxy.invokeSuper(obj, args);
	}

}

改成通用点的

package proxy;

import java.lang.reflect.Method;

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

public class CglibProxy implements MethodInterceptor {
	private CglibProxy() {
	}
	public static <T extends Object> Object newProxyInstance(Class<T> targetInstanceClazz){
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(targetInstanceClazz);
        enhancer.setCallback(new CglibProxy());
        return (Object) enhancer.create();//返回的对象是一个封装了"实现类"的代理类，是实现类的实例

    }

	@Override
	public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
		return proxy.invokeSuper(obj, args);
	}

}

　

测试　

package proxy;

public class CglibTest {
	public static void main(String[] args) {
		Women women = (Women) CglibProxy.newProxyInstance(Lily.class);
		women.eat();
		women.play();
	}

}

测试结果　

i'm Lily,i love eat banana
i'm Lily,i love swimming