(0基础保姆教程)-JavaEE开课啦!--13课程(Interception拦截器)-完结
一、Interception(拦截器)是什么?
拦截器(Interceptor)是一种用于在请求到达目标方法之前或之后执行特定逻辑的机制。它是基于Java反射机制,属于面向切面编程(AOP)的一种应用。拦截器可以用于多种应用场景,例如验证用户登录状态、权限验证、记录系统日志、通用处理等。
二、任务要求
1.在登录界面对用户名和密码进行验证
2.未登录状态下,直接访问main页面,拦截回login页面
3.在登录状态下,直接跳转到main页面,在页面显示用户名
三、实现代码
目录结构
1.创建Spring项目
2.在pom文件中引入相关依赖
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ljl</groupId>
<artifactId>SpringMVC_class_interceptor</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>SpringMVC_class_interceptor Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<!-- Spring 基础配置-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.3.10</version>
</dependency>
<!-- SpringMVC工具插件-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.10</version>
</dependency>
<!-- servlet插件-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.32</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.11</version>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter</artifactId>
<version>RELEASE</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.15.4</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.15.4</version>
</dependency>
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
</dependencies>
<build>
<finalName>SpringMVC_class_interceptor</finalName>
</build>
</project>
3.在Web.xml文件中配置相关依赖
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<!--允许访问jpg。 并且必须加在springmvc的servlet之前-->
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>*.jpg</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>chinese_encoder</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>chinese_encoder</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
4.创建spring-mvc.xml文件,对springmvc进行配置
<?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/beans
https://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">
<mvc:annotation-driven/>
<context:component-scan base-package="com.ljl.controller"/>
<bean class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping" />
<bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter" />
<!-- 配置视图解释器-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/pages/"/>
<property name="suffix" value=".jsp"/>
</bean>
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<property name="defaultEncoding" value="UTF-8"/>
<property name="maxUploadSize" value="2097152"/>
</bean>
<mvc:default-servlet-handler/>
<!-- 配置拦截器-->
<mvc:interceptors>
<bean class="com.ljl.interceptor.LoginInterceptor"/>
</mvc:interceptors>
</beans>
5.创建pages/login.jsp 和 pages/main.jsp前端界面
login.jsp
<%--
Created by IntelliJ IDEA.
User: ljl
Date: 2024/12/9
Time: 下午4:24
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="login" method="post">
<div>${msg}</div>
用户名:<input type="text" name="username"><br>
密 码:<input type="password" name="password"><br>
<input type="submit" value="登录">
</form>
</body>
</html>
main.jsp
<%--
Created by IntelliJ IDEA.
User: ljl
Date: 2024/12/9
Time: 下午4:23
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>main</title>
</head>
<body>
<ul>
<li>您好:${USER_SESSION.username}</li>
<li><a href="${pageContext.request.contextPath}/logout">退出</a> </li>
</ul>
</body>
</html>
6.创建Entity/UserEntity实体类
package com.ljl.Entity;
public class User {
private String username;
private String password;
public User() {
}
public User(String username, String password) {
this.username = username;
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
7.创建Controller/UserController控制器
package com.ljl.controller;
import com.ljl.Entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpSession;
@Controller
public class UserController {
@RequestMapping("/main")
public String toMainPage(){
return "main";
}
// 检查是否存在cookies,存在的话直接跳转主页
@RequestMapping("/tologin")
public String toLoginPage(HttpSession session){
if (session.getAttribute("USER_SESSION") != null){
return "main";
}
return "login";
}
@RequestMapping("/login")
public String login(User user, Model model, HttpSession session){
String username = user.getUsername();
String password = user.getPassword();
if (username != null && username.equals("pjl") && password != null && password.equals("123")){
session.setAttribute("USER_SESSION", user);
return "main";
}
model.addAttribute("msg", "用户名或密码错误!");
return "login";
}
@RequestMapping("/logout")
public String logout(HttpSession session){
session.invalidate();
return "redirect:tologin";
}
}
8.创建interceptor/LoginInterceptor拦截控制器*******
package com.ljl.interceptor;
import org.springframework.web.servlet.HandlerInterceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginInterceptor implements HandlerInterceptor {
public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
String uri = httpServletRequest.getRequestURI();
if (uri.indexOf("/login") >= 0){
return true;
}
HttpSession hs = httpServletRequest.getSession();
if (hs.getAttribute("USER_SESSION") != null){
return true;
}
httpServletRequest.setAttribute("msg", "没有登录!");
httpServletRequest.getRequestDispatcher("/WEB-INF/pages/login.jsp").forward(httpServletRequest, httpServletResponse);
return false;
}
}
四、运行测试
1.部署项目,对tomcat进行配置
2.进行账户验证
(http://localhost:8090/SpringMVC_class_interceptor_war_exploded/tologin)
错误账号:ljl 错误密码:123
正确账户:pjl 正确密码:123
3.成功登录后,退出登录,直接访问main页面,拦截回login页面
4.成功登录后,重新访问login页面,系统判断到已登录状态,直接跳转到main页面,显示用户名
五、本Java EE基础完结
原文地址:https://blog.csdn.net/pjlpjlpjl/article/details/144352825
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