上诉我们在（9）中
提出了问题，当我们的实体类的属性和mysql数据库的列名不一致时，出现的问题
那么 我们怎么解决实体类属性和数据库列名不对应？

解决办法2中:

方法1 取别名（执行效率最高）

运行结果出来，正确：

方法2 采用配置的方式 （开发效率变快）

测试结果成功:

目录结构：

3 结构和代码

• 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</groupId>
    <artifactId>day2-mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>
</project>

• log4j.properties

log4j.rootCategory=debug, CONSOLE, LOGFILE

log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30C %x - %m\n

• SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--首先是跟元素-->
<configuration>
    <!--配置环境 , 选择一个默认的环境mysql-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"></property>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=UTF-8" />
                <property name="username" value="root"></property>
                <property name="password" value=""></property>
            </dataSource>
                
        </environment>
    </environments>

    <!--配置映射文件的位置-->
    <mappers>
        <mapper resource="com/dao/UserDao.xml"></mapper>
    </mappers>

</configuration>

UserDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.dao.UserDao">
    <!--配置查询所有-->
    <select id="findAll" resultType="com.domain.User">
        select * from user;
    </select>
    
    <!--保存用户-->
    <insert id="saveUser" parameterType="com.domain.User">
        <!--配置插入操作后,获取插入数据的id-->
        <selectKey keyProperty="userId" keyColumn="id" resultType="int" order="AFTER">
            select last_insert_id();
        </selectKey>
        insert into user(username,address,sex,birthday) value(#{userName},#{userAddress},#{userSex},#{userBirthday});
    </insert>

    <!--更新用户-->
    <update id="updateUser" parameterType="com.domain.User">
        update user set username=#{userName},address=#{userAddress},sex=#{userSex},birthday=#{userBirthday} where id=#{userId};
    </update>

    <!--删除用户-->
    <delete id="deleteUser" parameterType="java.lang.Integer">
        delete from user where id = #{uid};
    </delete>

    <!--根据ID查询用户-->
    <select id="findById" parameterType="INT" resultType="com.domain.User">
        select * from user where id = #{uid};
    </select>

    <select id="findByName" parameterType="string" resultType="com.domain.User">

        <!--select * from user where username like #{name};-->
        select * from user where username like '%${value}%'
    </select>

    <!--获取用户的总记录条数-->
    <select id="findTotal" resultType="int">
        select count(id) from user;
    </select>

    <!--根据queryVo的条件查询用户-->
    <select id="findUserByVo" parameterType="com.domain.QueryVo" resultType="com.domain.User">
        select * from user where username like #{user.username};
    </select>

</mapper>

UserDao

package com.dao;

import com.domain.QueryVo;
import com.domain.User;

import java.util.List;

/**
 * 用户的持久层
 */
public interface UserDao {

    /**
     * 查询所有的用户
     */
    List<User> findAll();

    /**
     * 保存方法
     */
    void saveUser(User user);

    /**
     * 更新操作
     */
    void updateUser(User user);

    /**
     * 删除操作
     */
    void deleteUser(Integer userId);

    /**
     *  根据id查询用户信息
     */
    User findById(Integer userId);


    /**
     * 根据名称模糊查询信息
     */
    List<User> findByName(String username);

    /**
     * 查询总用户数
     */
    int findTotal();

    /**
     * 根据queryVo中的条件查询用户
     */
    List<User> findUserByVo(QueryVo vo);



}

QueryVo:

package com.domain;

public class QueryVo {

    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

User:

package com.domain;

import java.io.Serializable;

//让它实现序列化接口
public class User implements Serializable {


    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private String userBirthday;

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday='" + userBirthday + '\'' +
                '}';
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public String getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(String userBirthday) {
        this.userBirthday = userBirthday;
    }

}

MybatisTest

import com.dao.UserDao;
import com.domain.QueryVo;
import com.domain.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 org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

public class MybatisTest {


    private InputStream in;
    private SqlSession sqlSession;
    private UserDao userDao;

    @Before//用于在测试方法之前执行
    public void init()throws Exception{
        //1.读取配置文件，生成字节输入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.获取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.获取SqlSession对象
        sqlSession = factory.openSession();
        //4.获取dao的代理对象
        userDao = sqlSession.getMapper(UserDao.class);
    }

    @After//用于在测试方法之后执行
    public void destory()throws Exception{
        //5.提交事务
        sqlSession.commit();
        //6.释放资源
        sqlSession.close();
        in.close();
    }
    /**
     * 测试查询所有
     */
    @Test
    public void testFindAll(){
        //5.执行查询所有方法
        List<User> users = userDao.findAll();
        for(User user: users){
            System.out.println(user);
        }
    }

    /**
     * 测试保存操作
     */
    @Test
    public void testSave()throws Exception{
        User user = new User();
        user.setUserName("modify User ");
        user.setUserAddress("成都市");
        user.setUserSex("男");
        user.setUserBirthday("2019");
        System.out.println("保存操作之前:"+user);
        //5.执行查询所有方法
        userDao.saveUser(user);
        System.out.println("保存操作之后:"+user);
    }

    /**
     * 测试更新操作
     */
    @Test
    public void testUpdate(){
        User user = new User();
        user.setUserId(49);
        user.setUserName("update");
        user.setUserSex("male");
        user.setUserBirthday("2020");
        user.setUserAddress("chengdu");

        //5.执行保存方法
        userDao.updateUser(user);

    }

    /**
     * 测试删除操作
     */
    @Test
    public void testDelete(){
        //5.执行删除操作
        userDao.deleteUser(42);
    }


    /**
     * 测试根据ID查询用户
     */
    @Test
    public void testFindOne(){
        User user = userDao.findById(43);
        System.out.println(user);
    }

    /**
     * 测试模糊查询操作
     */
    @Test
    public void testFindByName(){
        List<User> users = userDao.findByName("王");
        for(User user: users){
            System.out.println(user);
        }
    }

    /**
     * 查询总记录条数
     */
    @Test
    public void testFindTotal(){
        int count = userDao.findTotal();
        System.out.println(count);
    }



    /**
     * 测试使用QueryVo作为查询对象
     */
    @Test
    public void testFindByVo(){
        QueryVo vo = new QueryVo();
        User user = new User();
        user.setUserName("%王%");
        vo.setUser(user);
        List<User> users = userDao.findUserByVo(vo);
        for(User u : users){
            System.out.println(u);
        }

    }
}