【Spring】SpringMVC之拦截器

时间：2022-01-14 18:57:26

Spring的HandlerMapping处理器支持拦截器应用。当需要为某些请求提供特殊功能时，例如实现对用户进行身份认证、登录检查等功能。

拦截器必须实现HandlerInterceptor接口，实现了这个接口就会重写三个方法preHandle()、postHandle()和afterCompletion()方法，关于这个三个方法的执行流程都在下面这张图片中：

【Spring】SpringMVC之拦截器
使用步骤:

1.  编写一个类 实现HandlerInterceptor接口

2.  配置applicationContext.xml

配置文件案例:

    <mvc:interceptors>

        <mvc:interceptor>

            <!--    要拦截的地址 -->

            <mvc:mapping path="/**"/>

            <!-- 匹配拦截地址 中的不拦截的地址

            <mvc:exclude-mapping path=""/>-->

            <!-- 使用的拦截器类 -->

            <bean class="cn.xdl.filter.MyFilter"></bean>

        </mvc:interceptor>

    </mvc:interceptors>

Demo

UserController.java文件：

package cn.xdl.controller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.View;

@Controller

public class UserController {

    @RequestMapping("/login.do")

    public ModelAndView userLogin(String uname,String upass){

        System.out.println(uname);

        System.out.println(upass);

        ModelAndView modelview=new ModelAndView("loginResult");

        return modelview;

    }

}

UserController.java

UserFilter.java文件：

package cn.xdl.user.filter;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;

import org.springframework.web.servlet.ModelAndView;

public class UserFilter implements HandlerInterceptor {

    @Override

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object arg2, Exception arg3)

            throws Exception {

    }

    @Override

    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object arg2, ModelAndView arg3)

            throws Exception {

    }

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {

        /*

         * return true 表示拦截通过

         * return false 表示拦截不通过

         *

         * 如果是拦截不通过用户的页面会出现一个大白屏，这个时候应该进行请求重定向，比如：response.sendRedirect("loginError.jsp")

         */

        String uname = request.getParameter("uname");

        String upass = request.getParameter("upass");

        //对用户的账号和密码进行简单验证

        if(uname==null||upass==null||uname.length()<6||upass.length()<6){

            //拦截  ,

            response.sendRedirect("loginError.jsp");

            return false;

        }

        return true;

    }

}

UserFilter.java

dispatcher_serverlet-servlet.xml文件：

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns:mvc="http://www.springframework.org/schema/mvc"

    xmlns:context="http://www.springframework.org/schema/context"

    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd

        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-4.3.xsd">

    <!--指定扫描包-->

    <context:component-scan base-package="cn"></context:component-scan>

    <!--开启扫描-->

    <mvc:annotation-driven/>

    <!--配置ModelAndView-->

    <bean id="viewResolve" class="org.springframework.web.servlet.view.InternalResourceViewResolver">

        <property name="viewClass" value="org.springframework.web.servlet.view.InternalResourceView"></property>

        <property name="prefix" value=""></property>

        <property name="suffix" value=".jsp"></property>

    </bean>

    <!--配置拦截器-->

    <mvc:interceptors>

        <mvc:interceptor>

                <!--     要拦截的地址，这里是拦截所有地址 -->

                <mvc:mapping path="/**"/>

                <!--

                匹配拦截地址中不用拦截的地址

                <mvc:exclude-mapping path=""/>

                -->

                <!-- 指定的拦截器类 -->

                <bean class="cn.xdl.user.filter.UserFilter"></bean>

        </mvc:interceptor>

    </mvc:interceptors>

</beans>

dispatcher_serverlet-servlet.xml

这里的dispatcher_serverlet-servlet.xml文件必须在WEB-INFO目录下，并且dispatcher_serverlet应该和web.xml中对应的<servlet-name>的值一致，详情可以参见SpringMVC的非注解配置的两种方式

web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">

  <display-name>SpringFilterTest</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

  </welcome-file-list>

  <servlet>

    <servlet-name>dispatcher_serverlet</servlet-name>

    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>dispatcher_serverlet</servlet-name>

    <url-pattern>*.do</url-pattern>

  </servlet-mapping>

  <filter>

    <filter-name>EncodingName</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>EncodingName</filter-name>

    <url-pattern>/*</url-pattern>

  </filter-mapping>

</web-app>

web.xml

loginError.jsp文件：

<%@ page language="java" contentType="text/html; charset=utf-8"

    pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>登录失败</title>

</head>

<body>

登录失败

</body>

</html>

loginError.jsp

loginResult.java文件

<%@ page language="java" contentType="text/html; charset=utf-8"

    pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>结果页面</title>

</head>

<body>

登录成功

</body>

</html>

loginResult.java

login.jsp文件

<%@ page language="java" contentType="text/html; charset=utf-8"

    pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>用户登录</title>

</head>

<body>

<form action="login.do" method="post">

用户名:<input type="text" name="uname" /><br/><br/>

密码:<input type="password" name="upass" /><br/><br/>

<input type="submit" value="登录" />

</form>

</body>

</html>

login.jsp

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