MyBatis备忘：查询数据库实现登录功能的一个演示

旧城等待， 2022-05-12 07:28 203阅读 0赞

*  复习：entity  DAO/DBHelper  service  action  jsp
 *  总结：使用mybatis后的区别：DBHelper里书写的是SqlSession，而不是自己来拿数据库连接了，当然这得写配置文件SqlMapConfig；service包里是一个接口对一个实现类，如IUserService，UserService，在接口实现类里，通过SqlSession的getMapper方法自动实现DAO层的UserMapper接口；DAO包里全部是接口；sql语句及与实体类的映射全部由mybatis里的配置文件完成，如User类对应就写一个User.xml文件。

## 代码演示 ##

*  jsp

<%@ 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>登录页</title>
    <link rel="stylesheet" type="text/css" href="css/login.css"/>
    <script type="text/javascript" src="js/jquery.js"></script>
    <script type="text/javascript"> $(function(){ $("input[type='submit']").mouseover(function(){ var nick = $("input:first").val(); var pwd = $("input:eq(1)").val(); if(nick == '' || pwd == ''){ $(this).attr("type","button"); }else{ $(this).attr("type","submit"); } }); }); </script>
    </head>
    <body>
    <div id="out">
        <form action="login.do" method="post">
        <ul>
            <li class="move"><input type="text" name="nick" placeholder="昵称"/></li>
            <li><input type="password" name="pwd" placeholder="密码"/></li>
            <li><input type="submit" value="登录"/></li>
            <li><a href="reg.jsp">我要注册？</a></li>
            <span></span>
        </ul>
        </form>
    </div>
    </body>
    </html>

*  action/web.xml

package com.frame.action;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.frame.entity.User;
    import com.frame.service.UserService;
    
    public class LoginAction extends HttpServlet { 
    
        /** * */
        private static final long serialVersionUID = 1L;
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            doPost(req, resp);
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            String nick = req.getParameter("nick");
            String pwd = req.getParameter("pwd");
            UserService uService = new UserService();
            User loginer = uService.findByNickAndPwd(nick, pwd);
            if(loginer != null){
                req.getSession().setAttribute("loginer", loginer);
                req.getRequestDispatcher("index.jsp").forward(req,resp);
            }else{
                resp.sendRedirect("login.jsp");
            }
    
        }
    
    }

<servlet>
        <servlet-name>loginAction</servlet-name>
        <servlet-class>com.frame.action.LoginAction</servlet-class>
      </servlet>
      <servlet-mapping>
        <servlet-name>loginAction</servlet-name>
        <url-pattern>/login.do</url-pattern>
      </servlet-mapping>

*  service

package com.frame.service;
    
    import org.apache.ibatis.session.SqlSession;
    
    import com.frame.dao.UserMapper;
    import com.frame.entity.User;
    import com.frame.util.DBHelper;
    
    public class UserService implements IUserService { 
        //dao层只提供了一个接口，并不需要我们自己实现，通过mybatis的session.getMapper()动态代理实例化对象
        private UserMapper userMapper;
    
        @Override
        public User findByNickAndPwd(String nick, String pwd) {
            SqlSession session = DBHelper.getSession();
            userMapper = session.getMapper(UserMapper.class);
            return userMapper.selectByNickAndPwd(nick, pwd);
        }
    
        @Override
        public void addUser(User u) {
            SqlSession session = DBHelper.getSession();
            userMapper = session.getMapper(UserMapper.class);
            userMapper.insert(u);
            session.commit();//不提交，数据不会写入数据库
            DBHelper.close(session);
        }
    
        @Override
        public User findByNick(String nick) {
            SqlSession session = DBHelper.getSession();
            userMapper = session.getMapper(UserMapper.class);
            User u = userMapper.selectByNick(nick);
            DBHelper.close(session);
            return u;
        }
    
    }

*  DAO

package com.frame.dao;
    
    import org.apache.ibatis.annotations.Param;
    
    import com.frame.entity.User;
    
    public interface UserMapper { 
    
        public User selectByNickAndPwd(@Param("nick") String nick,@Param("pwd") String pwd);
        public void insert(User u);
        public User selectByNick(String nick);
    }

*  entity/User.xml

package com.frame.entity;
    
    public class User {
        private int id;
        private String nick;
        private String pwd;
        private String name;
        private String sex;
        private String phone;
        private String addr;
        private String photo;
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getNick() {
            return nick;
        }
        public void setNick(String nick) {
            this.nick = nick;
        }
        public String getPwd() {
            return pwd;
        }
        public void setPwd(String pwd) {
            this.pwd = pwd;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getSex() {
            return sex;
        }
        public void setSex(String sex) {
            this.sex = sex;
        }
        public String getPhone() {
            return phone;
        }
        public void setPhone(String phone) {
            this.phone = phone;
        }
        public String getAddr() {
            return addr;
        }
        public void setAddr(String addr) {
            this.addr = addr;
        }
        public String getPhoto() {
            return photo;
        }
        public void setPhoto(String photo) {
            this.photo = photo;
        }
    
    
    }

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTD SQL Map 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
    <mapper namespace="com.frame.dao.UserMapper">
        <select id="selectByNickAndPwd" resultType="User">
        select * from user where nick=#{nick} and pwd=#{pwd}
        </select>
        <insert id="insert">
        insert into user(nick,pwd,name,sex,phone,addr,photo)values(#{nick},#{pwd},#{name},#{sex},#{phone},#{addr},#{photo})
        </insert>
        <select id="selectByNick" resultType="User">
        select * from user where nick=#{nick}
        </select>
    
    
    </mapper>

*  DBHelper

package com.frame.util;
    
    import java.io.IOException;
    import java.io.Reader;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    
    public class DBHelper { 
    
        private static SqlSessionFactory factory;
        //之所以将factory作为成员变量，而不在静态代码块里，是因为工厂是复用的，不用每次都创建
        //同理session不能作为成员变量，是因为session不能复用，如果共用一个会话，数据就相当于全部共享了
        static{
            SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
            try {
                Reader reader = Resources.getResourceAsReader("SqlMapConfig.xml");
                factory = factoryBuilder.build(reader);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        //获取数据库会话对象
        public static SqlSession getSession(){
            return factory.openSession();
        }
        //关闭数据库会话
        public static void close(SqlSession session){
            if(session != null){
                session.close();
            }
        }
    }

*  SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration PUBLIC "-//ibatis.apache.org//DTD SQL Map Config 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-config.dtd">
    <configuration>
    
        <typeAliases>
            <typeAlias type="com.frame.entity.User" alias="User"/>
            <typeAlias type="com.frame.entity.Province" alias="Province"/>
            <typeAlias type="com.frame.entity.City" alias="City"/>
            <typeAlias type="com.frame.entity.Street" alias="Street"/>
        </typeAliases>
        
        <environments default="e1">
            <environment id="e1">
                
                <transactionManager type="JDBC"></transactionManager>
                
                <dataSource type="POOLED">
                        
                    <property name="driver" value="com.mysql.jdbc.Driver"/> 
                    <property name="url" value="jdbc:mysql://localhost:3306/studysys"/> 
                    <property name="username" value="root"/>
                    <property name="password" value="root1205"/>
                </dataSource>
            </environment>  
        </environments>
        
        <mappers>
            <mapper resource="com/frame/entity/User.xml"/>
            <mapper resource="com/frame/entity/Province.xml"/>
            <mapper resource="com/frame/entity/City.xml"/>
            <mapper resource="com/frame/entity/Street.xml"/>
        </mappers>      
    </configuration>