springMVC的学习拦截器之验证用户登录案例

超、凢脫俗 2024-03-29 15:50 101阅读 0赞

#### 文章目录 ####

*  实现思路
 *  关于环境和配置文件
 *   *  pom
     *  spring的配置文件
     *  关于idea的通病/常见500错误的避坑
 *  实现步骤
 *   *  编写登陆页面
     *  编写Controller处理请求
     *  编写登录成功的页面
     *  编写登录拦截器

## 实现思路 ##

1.  有一个登录页面，需要写一个controller访问页面
2.  登陆页面提供填写用户名和密码的表单。需要在controller中进行判断处理，如果正确，向session中写入用户信息，返回登录成功
3.  拦截用户请求，判断用户是否登录。如果用户已经登录，就放行；否则，跳转到登录页面

## 关于环境和配置文件 ##

### pom ###

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.yang</groupId>
        <artifactId>springmvc-07-Interceptor</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-webmvc</artifactId>
                <version>5.3.18</version>
            </dependency>
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>servlet-api</artifactId>
                <version>2.5</version>
            </dependency>
            <dependency>
                <groupId>javax.servlet.jsp</groupId>
                <artifactId>jsp-api</artifactId>
                <version>2.2</version>
            </dependency>
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>jstl</artifactId>
                <version>1.2</version>
            </dependency>
    
        </dependencies>
    
    
        
        <build>
            <resources>
                <resource>
                    <directory>src/main/resources</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>true</filtering>
                </resource>
                <resource>
                    <directory>src/main/java</directory>
                    <includes>
                        <include>**/*.properties</include>
                        <include>**/*.xml</include>
                    </includes>
                    <filtering>true</filtering>
                </resource>
            </resources>
        </build>
    
    </project>

### spring的配置文件 ###

<?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"
           xmlns:mv="http://www.springframework.org/schema/cache"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            https://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/mvc
            https://www.springframework.org/schema/mvc/spring-mvc.xsd
            http://www.springframework.org/schema/cache
            http://www.springframework.org/schema/cache/spring-cache.xsd">
        
        <context:component-scan base-package="com.yang.controller"/>
    
        
        <mvc:default-servlet-handler />
        <mvc:annotation-driven />
        
    
    
        
        <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>
    
        
        <mvc:interceptors>
            <mvc:interceptor>
                <mvc:mapping path="/**"/>
                <bean id="loginInterceptor" class="com.yang.config.LoginInterceptor"/>
            </mvc:interceptor>
        </mvc:interceptors>
    
    </beans>

### 关于idea的通病/常见500错误的避坑 ###

*  就是要在***项目结构–>工件中***，手动配置lib目录导入所有的依赖  
    ![在这里插入图片描述][a81afdff978f4498acaf279290616b7b.png]

## 实现步骤 ##

### 编写登陆页面 ###

<%--
      Created by IntelliJ IDEA.
      User: HP
      Date: 2022/8/1
      Time: 19:40
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>login</title>
    </head>
    <body>
    <form action="${pageContext.request.contextPath}/user/login">
        用户名：<input type="text" name="username" required> <br>
        密码： <input type="password" name="pwd" required> <br>
        <input type="submit" value="提交">
    </form>
    
    </body>
    </html>

### 编写Controller处理请求 ###

import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import javax.servlet.http.HttpSession;
    
    /**
     * @author 缘友一世
     * @date 2022/8/1-20:05
     */
    @Controller
    @RequestMapping("/user")
    public class LoginController {
        
        //跳转到登陆页面
        @RequestMapping("/jumpLogin")
        public String jumpLogin() throws Exception {
        
            return "login";
        }
        //跳转到成功页面
        @RequestMapping("/jumpSuccess")
        public String jumpSuccess() throws Exception {
        
            return "success";
        }
        //登陆提交
        @RequestMapping("/login")
        public String login(HttpSession session, String username, String pwd) throws Exception {
        
            // 向session记录用户身份信息
            //System.out.println("接收前端==="+username);
            session.setAttribute("user", username);
            session.setAttribute("password", pwd);
            return "success";
        }
        //退出登陆
        @RequestMapping("logout")
        public String logout(HttpSession session) throws Exception {
        
            // session 过期
            session.invalidate();
            return "login";
        }
    
    }

### 编写登录成功的页面 ###

<%--
      Created by IntelliJ IDEA.
      User: HP
      Date: 2022/8/1
      Time: 20:28
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>success</title>
    </head>
    <body>
        <h1>登录成功页面</h1>
        <hr>
        恭喜，${user}，登陆成功
        <a href="${pageContext.request.contextPath}/user/logout">注销</a>
    </body>
    </html>

### 编写登录拦截器 ###

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;
    
    /**
     * @author 缘友一世
     * @date 2022/8/1-20:30
     */
    public class LoginInterceptor implements HandlerInterceptor {
        
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        
            // 如果是登陆页面则放行
            //System.out.println("uri: " + request.getRequestURI());
            //request.getRequestURI() 返回除去host（域名或者ip）部分的路径
            //逻辑判断 路径中是否包含login，确定是否在登陆页面 如果是，就通行
            if (request.getRequestURI().contains("login")) {
        
                return true;
            }
            HttpSession session = request.getSession();
            // 如果用户已登陆也放行
            if(session.getAttribute("user") != null) {
        
                return true;
            }
            // 用户没有登陆跳转到登陆页面
            request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
            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 {
        
    
        }
    }

*  最后启动tomcat进行测试

[a81afdff978f4498acaf279290616b7b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/28/0742135f72e74bb88e6e14388688f960.png