Spring拦截器

1.拦截器原理同filter类似？

2.拦截器的实现？

  1）首先定义一个类，该类需要继承自HandlerInterceptor接口。

package com.gxa.bj.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class UserInterceptor implements HandlerInterceptor{

	@Override
	public void afterCompletion(HttpServletRequest arg0,
			HttpServletResponse arg1, Object arg2, Exception arg3)
			throws Exception {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1,
			Object arg2, ModelAndView arg3) throws Exception {
		// TODO Auto-generated method stub
		
	}

	@Override
	public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1,
			Object arg2) throws Exception {
		HttpSession session=arg0.getSession();
		if(session.getAttribute("userInfo")==null){
			arg0.getRequestDispatcher("../login.jsp").forward(arg0, arg1);
			return false;
		}else{
			return true;
		}
	}

}

2）配置拦截器：在springmvc.xml中配置：特别需要注意在springmvc的声明里需要更改，更改之后的配置信息如下：

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"
        default-autowire="byName"
        >

3）编写相应的拦截器的拦截路径，在springmvc.xml中配置如下：

<mvc:interceptors>
		 <!--使用bean定义一个Interceptor，直接定义在mvc:interceptors根下面的			Interceptor将拦截所有的请求  -->
		<mvc:interceptor>
		    <span style="color:#ffcc66;"><mvc:mapping path="/admin/*.action"/>  </span>
		    <bean class="com.gxa.bj.interceptor.UserInterceptor">
		    </bean>
		</mvc:interceptor>
</mvc:interceptors>

注意：黄色的这部分的路径配置，表示的是拦截器拦截的是这个路径下的。*表示任意的。

4）示例，比如现在做一个AdminUser的控制器，需要由拦截器来拦截该控制器。

@Controller
@RequestMapping(value="/admin")
public class AdminUserAction {
   @RequestMapping(value="/user.action")
   public void user(){
	   System.out.println("请求过来了");
   }
   @RequestMapping(value="/delete.action")
   public void delete(){
	   System.out.println("删除的请求");
   }
}