拦截器实验步骤

开发环境：
IDEA

1. 创建工程文件，导入web支持

2.在web.xml当中导入spring以及servlet

 <servlet><servlet-name>springmvc</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:applicationContext.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>springmvc</servlet-name><url-pattern>/</url-pattern></servlet-mapping><!--避免中文乱码--><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>

4. 编写applicationContext.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:context="http://www.springframework.org/schema/context"xmlns:mvc="http://www.springframework.org/schema/mvc"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttps://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/mvchttps://www.springframework.org/schema/mvc/spring-mvc.xsd"><context:component-scan base-package="com.zengwei.controller"/><!--    静态资源过滤--><mvc:default-servlet-handler/><!--    json乱码处理--><mvc:annotation-driven><mvc:message-converters register-defaults="true"><bean class="org.springframework.http.converter.StringHttpMessageConverter"><constructor-arg value="UTF-8"/></bean><bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"><property name="objectMapper"><bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"><property name="failOnEmptyBeans" value="false"/></bean></property></bean></mvc:message-converters></mvc:annotation-driven><!--    视图解析器--><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver"><property name="prefix" value="/WEB-INF/jsp/"/><property name="suffix" value=".jsp"/></bean>
</beans>

5. 构造目录结构

创建包：com.zengwei.controller

至此基本的项目架构已经搭好，可启动tomcat进行测试，注意在项目当中加入lib目录同时导入依赖文件

6. 创建拦截器的包，在该包下新建拦截器：MyIntercepter

package com.zengwei.intercepter;import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class MyIntercepter implements HandlerInterceptor {//此函数返回值为true 则表示执行下一个拦截器，放行//若为false则表示不放行public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {return false;}public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {}public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {}
}

7. 测试代码

package com.zengwei.intercepter;import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class MyIntercepter implements HandlerInterceptor {//此函数返回值为true 则表示执行下一个拦截器，放行//若为false则表示不放行public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("==========>处理前");return true;}//后面两个负责产生拦截日志public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("==========>处理后");}public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("==========》清理");}
}

8. 对设置的拦截器进行注册

//在applicationContext.xml文件当中加入
<!--    拦截器-->
<mvc:interceptors><mvc:interceptor>
<!--        此时文件下所有的文件都会拦截，具体拦截哪个controller在path可以具体指定--><mvc:mapping path="/**"/><bean class="com.zengwei.intercepter.MyIntercepter"/></mvc:interceptor>
</mvc:interceptors>
</beans>

实例：登录验证

1. 创建工程文件，导入web支持并写入相关配置

 <servlet><servlet-name>springmvc</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:applicationContext.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>springmvc</servlet-name><url-pattern>/</url-pattern></servlet-mapping><!--避免中文乱码--><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>

2.编写applicationContext.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:context="http://www.springframework.org/schema/context"xmlns:mvc="http://www.springframework.org/schema/mvc"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttps://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/mvchttps://www.springframework.org/schema/mvc/spring-mvc.xsd"><context:component-scan base-package="com.zengwei.controller"/>
<!--    静态资源过滤--><mvc:default-servlet-handler/><mvc:annotation-driven><mvc:message-converters register-defaults="true"><bean class="org.springframework.http.converter.StringHttpMessageConverter"><constructor-arg value="UTF-8"/></bean><bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"><property name="objectMapper"><bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"><property name="failOnEmptyBeans" value="false"/></bean></property></bean></mvc:message-converters></mvc:annotation-driven><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver"><property name="prefix" value="/WEB-INF/jsp/"/><property name="suffix" value=".jsp"/></bean>

3. 在原来的包下面创建LoginInterceptor.java拦截器

package com.zengwei.intercepter;import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;public class LoginInterceptor implements HandlerInterceptor {public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {HttpSession session = request.getSession();//放行的判断，1.有session但没有东西，2. 有session有东西if(request.getRequestURI().contains("login")){return true;}if(session.getAttribute("loginuser")!=null){return true;}//判断什么情况下没有登录，1.没有session肯定没有登录，request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request,response);return false;}
}

4. 注册拦截器

在applicationContext当中加入

<!--    拦截器-->
<mvc:interceptors><mvc:interceptor><mvc:mapping path="/User/**"/><bean class="com.zengwei.intercepter.LoginInterceptor"/></mvc:interceptor>
</mvc:interceptors>

5. 编写对应的controller

//LoginController
package com.zengwei.controller;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpSession;
@Controller
@RequestMapping("/User")
public class LoginController {@RequestMapping("/login")public String Login(HttpSession session, String username, String passwd, Model model){//正常登录后需要把用户信息存入session当中方便以后或者用户访问期间调入信息session.setAttribute("loginuser",username);model.addAttribute("name",username);return "main";}@RequestMapping("/main")public String Main(){return "main";}@RequestMapping("/tologin")public String toLogin(){return "login";}@RequestMapping("/goout")public String goout(HttpSession session){session.removeAttribute("loginuser");return "main";}
}

6. 前端界面

//index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html><head><title>$Title$</title></head><body><h3><a href="${pageContext.request.contextPath}/User/tologin">登录</a></h3><h3><a href="${pageContext.request.contextPath}/User/main">首页</a></h3></body>
</html>

//main.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>首页</title>
</head>
<body>
<h1>首页
</h1>
<span>${name}</span>
<p><a href="${pageContext.request.contextPath}/User/goout">注销</a></p>
</body>
</html>

//login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>登录页面</title>
</head>
<body><form action="${pageContext.request.contextPath}/User/login" method="post">用户名:<input type="text" name="username" />密码：<input type="text" name="userpwd"/><input type="submit" value="提交" /></form>
</body>
</html>