spring基础学习（六）——用动态代理实现拦截器

以你之姓@ 2022-06-01 11:43 170阅读 0赞

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：

![SouthEast][]

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

[SouthEast]: /images/20220601/54598f04ae0c4bd5b1579fcd2f0838dd.png