SpringMVC—拦截器和过滤器

一、自定义过滤器

1. MyFilter.java

   package com.filter;
   
   import javax.servlet.*;
   import java.io.IOException;
   
   public class MyFilter implements Filter {
       @Override
       public void init(FilterConfig filterConfig) throws ServletException {
           System.out.println("MyFilter---init");
       }
   
       @Override
       public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
           System.out.println("MyFilter---doFilter");
           filterChain.doFilter(servletRequest, servletResponse);
       }
   
       @Override
       public void destroy() {
           System.out.println("MyFilter---destroy");
       }
   }
   
   

2. web.xml

   <filter>
       <filter-name>myFilterfilter-name>
       <filter-class>com.filter.MyFilterfilter-class>
   filter>
   <filter-mapping>
       <filter-name>myFilterfilter-name>
       <url-pattern>/*url-pattern>
   filter-mapping>
   

二、自定义拦截器

1. MyInterceptor.java

   package com.interceptor;
   
   import org.springframework.web.servlet.HandlerInterceptor;
   import org.springframework.web.servlet.ModelAndView;
   
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   
   /**
    * com.interceptor
    *
    * @author sjh
    * @version 1.0
    */
   public class MyInterceptor implements HandlerInterceptor {
       @Override
       public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
           System.out.println("MyInterceptor ---prehandle");
           return true;
       }
   
       @Override
       public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
           System.out.println("MyInterceptor ---postHandle");
       }
   
       @Override
       public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
           System.out.println("MyInterceptor ---afterCompletion");
       }
   }
   
   

2. applicationContext.xml

   <mvc:interceptors>
       <bean class="com.interceptor.MyInterceptor"/>
   mvc:interceptors>
   

3. TestController

   @Controller
   public class TestController {
   
       @RequestMapping("test")
       public String test() {
           System.out.println("test");
           return "success";
       }
   }
   

4. success.jsp

   <%@ page contentType="text/html;charset=UTF-8" language="java" %>
   
   
       
   
   
   <% System.out.println("success.jsp");%>
   success
   
   
   

5. 总结
   控制台输出顺序如下：

   MyInterceptor—prehandle
   test
   MyInterceptor—postHandle
   success.jsp
   MyInterceptor—afterCompletion

   根据控制台输出顺序可知拦截器的执行顺序如下
   拦截器的preHandle方法----》执行目标方法----》执行拦截器的postHandle方法----》执行页面跳转----》执行拦截器的afterCompletion方法

6. 需注意：
   （1）如果prehandle方法返回值 为false，那么意味着不放行，那么就会造成后续的所有操作都中断
   （2）如果执行到方法中出现异常，那么后续流程不会处理但是afterCompletion方法会执行

三、过滤器和拦截器的关系

1. 包含关系
   

2. 执行流程
   

四、过滤器和拦截器的区别

• 过滤器是基于函数回调的，而拦截器是基于java反射的
• 过滤器依赖于servlet容器，而拦截器不依赖与Servlet容器
• 过滤器几乎对所有的请求都起作用，而拦截器只能对action请求起作用
  ​

五、多个过滤器和拦截器的关系

1. 运行结果

   FirstFilter—doFilter
   SecondFilter—doFilter
   FirstInterceptor—prehandle
   SecondInterceptor—prehandle
   test
   SecondInterceptor—postHandle
   FirstInterceptor—postHandle
   success.jsp
   SecondInterceptor—afterCompletion
   FirstInterceptor—afterCompletion