SpringMVC拦截器

SpringMVC拦截器

过滤器和拦截器的区别
（1）过滤器是Servlet的一部分，javaWeb工程都可以用
过滤器再url-patttern中配置/*之后，可以对所有要访问的资源进行来拦截
（2）拦截器是Springmvc自己的
拦截器它是会拦截访问的控制方法，如果访问的是Jsp,html,css等是不会进行拦截的。
经过拦截器才能到Controller,即拦截器只能拦截Controller中的方法

步骤：
1.编写拦截器（需实现接口HandlerInterceptor），
2.配置拦截器

代码如下：
1.Controller类

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping("/testInterceptor")
    public String testInterceptor(){
        System.out.println("testInterceptor执行了");
        return "success";
    }
}

2.配置文件web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <!--配置前端控制器-->
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <!--配置解决中文乱码的过滤器-->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>

3.Springmvc配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">
    <!--开启注解扫描-->
    <context:component-scan base-package="com.selan"></context:component-scan>

    <!--视图解析器-->
    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/pages/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <!--前端控制器，哪些静态资源不拦截-->
    <mvc:resources location="/js/" mapping="/js/**"/>

    <!--配置拦截器-->
    <mvc:interceptors>
        <!--配置具体的拦截器-->
        <mvc:interceptor>
            <!--要拦截的具体方法-->
            <mvc:mapping path="/user/**"/>
            <!--不要拦截的方法-->
            <!--<mvc:exclude-mapping path=""-->

            <!--配置拦截器对象-->
            <bean class="com.selan.interceptor.MyInterceptor"></bean>
        </mvc:interceptor>
    </mvc:interceptors>
    <!--开启SringMVC框架注解的支持  生效类型转换-->
    <mvc:annotation-driven/>

</beans>

4.自定义拦截器类

package com.selan.interceptor;

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

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

/**
 * @author Selan
 * @data 2020/3/2-10:01
 */

/*
 * 自定义拦截器*/
public class MyInterceptor implements HandlerInterceptor {

    /*
    * 预处理器 Controller执行方法前
    * return true放行，执行下一个拦截器，如果没有，执行controller中的方法
    * reruen false不放行，
    *
    * */
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("MyInterceptor1执行了...前");
         //直接跳转到某个页面
//        request.getRequestDispatcher("/pages/error.jsp").forward(request,response);
        return true;
    }
    /*
    * 后处理的方法，controller方法执行后，success.jsp执行之前
    *
    * */
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("MyInterceptor1执行了...后");
//        request.getRequestDispatcher("/pages/error.jsp").forward(request,response);
    }
    /*
    *
    * success.jsp页面执行后，该方法会执行*/
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("MyInterceptor1执行了...最后");
    }
}

5.JSP页面
（1）index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>拦截器</h1>
<a href="user/testInterceptor">拦截器</a>
</body>
</html>

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
   <h1>执行成功</h1>
   <%System.out.println("success.jsp执行了...");%>
</body>
</html>

error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<h1>错误页面</h1>
</body>
</html>

代码较为简单，理解整个逻辑过程即可