1.1 用户登录 1.1.1 需求分析 用户在登录页面输入用户名和密码，提交请求给LoginServlet在LoginServlet中接收请求和数据[用户名和密码]在LoginServlt中通过my
LoginServletLoginServlet中接收请求和数据[用户名和密码]LoginServlt中通过mybatis实现调用UserMapper来根据用户名和密码查询数据库表User对象中进行返回LoginServlet中判断返回的User对象是否为nullnul，说明根据用户名和密码没有查询到用户，则登录失败，返回"登录失败"数据给前端null，则说明用户存在并且密码正确，则登录成功，返回"登录成功"数据给前端
1 将sql语句执行下:
2 创建User.java实体类
package com.dcxuexi.pojo;public class User { private Integer id; private String username; private String passWord; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } 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{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + '}'; }}pom.xml导入Mybatis和Mysql驱动坐标 <dependency> <groupId>org.mybatisgroupId> <artifactId>mybatisartifactId> <version>3.5.10version> dependency> <dependency> <groupId>mysqlgroupId> <artifactId>mysql-connector-javaartifactId> <version>8.0.30version> dependency>mybatis-config.xml核心配置文件，UserMapper.xml映射文件，UserMapper接口1 在resources目录下创建mybatis-config.xml配置文件
DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "Http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration> <typeAliases> <package name="com.dcxuexi.pojo"/> typeAliases> <environments default="development"> <environment id="development"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql:///db1?useSSL=false&useServerPrepStmts=true"/> <property name="username" value="root"/> <property name="password" value="1234"/> dataSource> environment> environments> <mappers> <package name="com.dcxuexi.mapper"/> mappers>configuration>2 在com.dcxuexi.mapper包下创建UserMapper接口
package com.dcxuexi.mapper;public interface UserMapper {}3 resources目录下创建UserMapper.xml
注意：在resources下创建UserMapper.xml的目录时，要使用/分割
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.dcxuexi.mapper.UserMapper">mapper>至此我们所需要的环境就都已经准备好了，具体该如何实现?
UserMapper接口中提供一个根据用户名和密码查询用户对象的方法package com.dcxuexi.mapper;import com.dcxuexi.pojo.User;import org.apache.ibatis.annotations.Param;public interface UserMapper { User select(@Param("username") String username, @Param("password") String password);}UserMapper.xml实现根据用户名和密码查询用户对象。
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.dcxuexi.mapper.UserMapper"> <select id="select" resultType="com.dcxuexi.pojo.User"> select * from tb_user where username = #{username} and password = #{password} select>mapper>说明
@Param注解的作用：用于传递参数,是方法的参数可以与SQL中的字段名相对应。
login.htmlDOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>logintitle> <link href="CSS/login.css" rel="stylesheet">head><body><div id="loginDiv"> <fORM action="/request_demo/loginServlet" method="post" id="form"> <h1 id="loginMsg">LOGIN INh1> <p>Username:<input id="username" name="username" type="text">p> <p>Password:<input id="password" name="password" type="password">p> <div id="subDiv"> <input type="submit" class="button" value="login up"> <input type="reset" class="button" value="reset"> <a href="reGISter.html">没有账号？点击注册a> div> form>div>body>html>LoginServlet@WebServlet("/loginServlet")public class LoginServlet extends httpservlet { @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1. 接收用户名和密码 String username = request.getParameter("username"); String password = request.getParameter("password"); //2. 调用MyBatis完成查询 //2.1 获取SqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //2.2 获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //2.3 获取Mapper UserMapper userMapper = sqlSession.getMapper(UserMapper.class); //2.4 调用方法 User user = userMapper.select(username, password); //2.5 释放资源 sqlSession.close(); //获取字符输出流，并设置content type response.setContentType("text/html;charset=utf-8"); PrintWriter writer = response.getWriter(); //3. 判断user释放为null if(user != null){ // 登陆成功 writer.write("登陆成功"); }else { // 登陆失败 writer.write("登陆失败"); } } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request, response); }}1 如果用户名和密码输入错误，则
2 如果用户名和密码输入正确，则
至此用户的登录功能就已经完成了。
RegisterServletRegisterServlet中接收请求和数据[用户名和密码]RegisterServlet中通过Mybatis实现调用UserMapper来根据用户名查询数据库表User对象中进行返回RegisterServlet中判断返回的User对象是否为nullnul，说明根据用户名可用，则调用UserMapper来实现添加用户null，则说明用户不可以，返回"用户名已存在"数据给前端编写UserMapper提供根据用户名查询用户数据方法和添加用户方法
package com.dcxuexi.mapper;import com.dcxuexi.pojo.User;import org.apache.ibatis.annotations.Param;public interface UserMapper { User select(@Param("username") String username, @Param("password") String password); User selectByUsername(String username); void add(User user);}UserMapper.xml实现方法
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.dcxuexi.mapper.UserMapper"> <select id="select" resultType="com.dcxuexi.pojo.User"> select * from tb_user where username = #{username} and password = #{password} select> <select id="selectByUsername" resultType="com.dcxuexi.pojo.User"> select * from tb_user where username = #{username} select> <insert id="add"> insert into tb_user values(null,#{username},#{password}) insert>mapper>register.htmlDOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>欢迎注册title> <link href="css/register.css" rel="stylesheet">head><body><div class="form-div"> <div class="reg-content"> <h1>欢迎注册h1> <span>已有帐号？span> <a href="login.html">登录a> div> <form id="reg-form" action="/request_demo/registerServlet" method="post"> <table> <tr> <td>用户名td> <td class="inputs"> <input name="username" type="text" id="username"> <br> <span id="username_err" class="err_msg" style="display: none">用户名不太受欢迎span> td> tr> <tr> <td>密码td> <td class="inputs"> <input name="password" type="password" id="password"> <br> <span id="password_err" class="err_msg" style="display: none">密码格式有误span> td> tr> table> <div class="buttons"> <input value="注 册" type="submit" id="reg_btn"> div> <br class="clear"> form>div>body>html>RegisterServlet类package com.dcxuexi.web;import com.dcxuexi.mapper.UserMapper;import com.dcxuexi.pojo.User;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.InputStream;@WebServlet("/registerServlet")public class RegisterServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1. 接收用户数据 String username = req.getParameter("username"); String password = req.getParameter("password"); //封装用户对象 User user = new User(); user.setUsername(username); user.setPassword(password); //2. 调用mapper 根据用户名查询用户对象 //2.1 获取SqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //2.2 获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //2.3 获取Mapper UserMapper userMapper = sqlSession.getMapper(UserMapper.class); //2.4 调用方法 User user2 = userMapper.selectByUsername(username); resp.setContentType("text/html;charset=utf-8"); //3. 判断用户对象释放为null if (user2 == null){ // 用户名不存在，添加用户 userMapper.add(user); // 提交事务 sqlSession.commit(); // 释放资源 sqlSession.close(); resp.getWriter().write("用户注册成功"); }else { // 用户名存在，给出提示信息 resp.getWriter().write("用户名已存在"); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); }}
1 如果测试成功，则在数据库中就能查看到新注册的数据
2 如果用户已经存在，则在页面上展示 用户名已存在 的提示信息
SqlSessionFactory工具类抽取上面两个功能已经实现，但是在写Servlet的时候，因为需要使用Mybatis来完成数据库的操作，所以对于Mybatis的基础操作就出现了些重复代码，如下
String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);有了这些重复代码就会造成一些问题:
SqlSessionFactory工厂类进行重复创建 那如何来优化呢？
有了这两个方向后，代码具体该如何编写？
package com.dcxuexi.util;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import java.io.IOException;import java.io.InputStream;public class SqlSessionFactoryUtils { private static SqlSessionFactory sqlSessionFactory; static { //静态代码块会随着类的加载而自动执行，且只执行一次 try { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } public static SqlSessionFactory getSqlSessionFactory(){ return sqlSessionFactory; }}工具类抽取以后，以后在对Mybatis的SqlSession进行操作的时候，就可以直接使用
SqlSessionFactory sqlSessionFactory =SqlSessionFactoryUtils.getSqlSessionFactory();这样就可以很好的解决上面所说的代码重复和重复创建工厂导致性能低的问题了。
LoginServlet类优化如下：
package com.dcxuexi.web;import com.dcxuexi.mapper.UserMapper;import com.dcxuexi.pojo.User;import com.dcxuexi.util.SqlSessionFactoryUtils;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;@WebServlet("/loginServlet")public class LoginServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1. 接收用户名和密码 String username = req.getParameter("username"); String password = req.getParameter("password"); System.out.println("username = " + username); //2. 调用MyBatis完成查询 //2.1 获取SqlSessionFactory对象 //String resource = "mybatis-config.xml"; //InputStream inputStream = Resources.getResourceAsStream(resource); //SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory(); //2.2 获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //2.3 获取Mapper UserMapper userMapper = sqlSession.getMapper(UserMapper.class); //2.4 调用方法 User user = userMapper.select(username, password); //2.5 释放资源 sqlSession.close(); //获取字符输出流，并设置content type resp.setContentType("text/html;charset=utf-8"); PrintWriter writer = resp.getWriter(); if (user!=null){ // 登陆成功 writer.write(username+"登陆成功"); }else { // 登陆失败 writer.write("登陆失败"); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); }}RegisterServlet类优化如下：
package com.dcxuexi.web;import com.dcxuexi.mapper.UserMapper;import com.dcxuexi.pojo.User;import com.dcxuexi.util.SqlSessionFactoryUtils;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.InputStream;@WebServlet("/registerServlet")public class RegisterServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1. 接收用户数据 String username = req.getParameter("username"); String password = req.getParameter("password"); //封装用户对象 User user = new User(); user.setUsername(username); user.setPassword(password); //2. 调用mapper 根据用户名查询用户对象 //2.1 获取SqlSessionFactory对象 //String resource = "mybatis-config.xml"; //InputStream inputStream = Resources.getResourceAsStream(resource); //SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory(); //2.2 获取SqlSession对象 SqlSession sqlSession = sqlSessionFactory.openSession(); //2.3 获取Mapper UserMapper userMapper = sqlSession.getMapper(UserMapper.class); //2.4 调用方法 User user2 = userMapper.selectByUsername(username); resp.setContentType("text/html;charset=utf-8"); //3. 判断用户对象释放为null if (user2 == null){ // 用户名不存在，添加用户 userMapper.add(user); // 提交事务 sqlSession.commit(); // 释放资源 sqlSession.close(); resp.getWriter().write("用户注册成功"); }else { // 用户名存在，给出提示信息 resp.getWriter().write("用户名已存在"); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); }}来源地址：https://blog.csdn.net/qq_37726813/article/details/128514400
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本文标题: JavaWeb：用户注册登录案例
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