spring基础学习（六）——用动态代理实现拦截器

基于JDK动态代理实现拦截器

1.目标类接口：

package net.seehope.springioc.proxy;

public interface Targe {

	public void sayHallo();
}

2.目标类：

public class TargeImpl implements Targe{

	public void sayHallo() {
		System.out.println("我是明星我很大牌");
	}

}

3.拦截器接口：

public interface Interceptor {

	/**
	 * 
	 * @param target 目标类
	 * @param proxy  代理类
	 * @param method 方法
	 * @param ags    方法参数
	 * @return
	 */
	public boolean before(Object target,Object proxy,Method method,Object[] ags);
	
	/**
	 * 
	 * @param target 目标类
	 * @param proxy  代理类
	 * @param method 方法
	 * @param ags    方法参数
	 * @return
	 */
	public void around(Object target,Object proxy,Method method,Object[] ags);
	
	/**
	 * 
	 * @param target 目标类
	 * @param proxy  代理类
	 * @param method 方法
	 * @param ags    方法参数
	 * @return
	 */
	public void after(Object target,Object proxy,Method method,Object[] ags);
	
}

4.拦截器实现类：

拦截器1：

package net.seehope.springioc.proxy;

import java.lang.reflect.Method;

public class TargetInterceptor implements Interceptor{

	public boolean before(Object target, Object proxy, Method method, Object[] ags) {
		System.out.println("前置拦截-- 1");
		return false;
	}

	public void around(Object target, Object proxy, Method method, Object[] ags) {
		System.out.println("环绕拦截 -- 1");
		
	}

	public void after(Object target, Object proxy, Method method, Object[] ags) {
		System.out.println("后置拦截 -- 1");
		
	}

}

拦截器2：

import java.lang.reflect.Method;

public class TargetInterceptor2 implements Interceptor{

	public boolean before(Object target, Object proxy, Method method, Object[] ags) {
		System.out.println("前置拦截--2");
		return true;
	}

	public void around(Object target, Object proxy, Method method, Object[] ags) {
		// TODO Auto-generated method stub
		System.out.println("环绕拦截--2");
		
	}

	public void after(Object target, Object proxy, Method method, Object[] ags) {
		// TODO Auto-generated method stub
		System.out.println("后置拦截 --2");
	}

}

5、jdk动态代理的代码实现

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

public class JDKProxyInterceptor implements InvocationHandler{

	//目标类
	private Object target = null;
	//拦截器全限定名
	private String interceptorClass = null;
	
	public JDKProxyInterceptor() {
		super();
		// TODO Auto-generated constructor stub
	}

	public JDKProxyInterceptor(Object target, String interceptorClass) {
		super();
		this.target = target;
		this.interceptorClass = interceptorClass;
	}
	public Object bind(Object target,String interceptorClass){
		return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), new JDKProxyInterceptor(target,interceptorClass));
	}

	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		if(interceptorClass == null){
			System.out.println("不需要拦截器");
			return method.invoke(target, args);
		}
		Object result = null;
		
		Interceptor interceptor = (Interceptor) Class.forName(interceptorClass).newInstance();
		
		if(interceptor.before(target, proxy, method, args)){
			result = method.invoke(target, args);
		}else{
			interceptor.around(target, proxy, method, args);
		}
		interceptor.after(target, proxy, method, args);
		return result;
	}

}

6.测试类：

import org.junit.Test;

public class ProxyText {

	@Test
	public void JdkProxyText(){
		
		JDKProxyInterceptor example = new JDKProxyInterceptor();
		Targe proxyTarge = (Targe) example.bind(new TargeImpl(), "net.seehope.springioc.proxy.TargetInterceptor");
		Targe proxyTarge2 = (Targe) example.bind(proxyTarge, "net.seehope.springioc.proxy.TargetInterceptor2");
		
		proxyTarge2.sayHallo();
	}
}

7.测试结果：

结果分析:

 首先，传入了目标类和拦截器1地址生成了代理类protyTarge,然后再将protyTarge和拦截器2地址生成代理类protyTarge2，protyTarge2的代理增强方法invoke()判断拦截器2before()返回true, 执行 代理类protyTarge.invoke(), protyTarge的invoke()判断拦截器1.before()返回false，执行拦截器1.around(),然后执行拦截器1.after（），返回目标类执行结果，拦截器2执行after()方法，返回目标类执行结果

CGlib代理实现拦截器与JDK实现类似，不再做专门介绍