MyBatis_Study_003(字段名与属性名称不一致,resultMap)

Posted 2020-10-16 carryLess

源码:https://github.com/carryLess/mbtsstd-003

1.主配置文件

<?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">
<!-- (以上)文件头在解压的文件夹中mybatis-3.4.4.pdf文件中搜索mybatis-3-config.dtd即可得到 -->
<configuration>

    <!-- 指定属性配置文件 -->
    <properties resource="jdbc.properties" />
    <!--
        配置类的别名,我建议使用package这种写法
        这样写会将该包中所有类的简单类名配置为别名,简单方便
        ,还有别的写法,自行google
     -->
    <typeAliases>
        <package name="model" />
    </typeAliases>
    <!-- 配置MyBatis运行环境 -->
    <environments default="development">
        <environment id="development">
            <!-- 使用JDBC事务管理 -->
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 注册映射文件 -->
    <mappers>
        <mapper resource="dao/mapper.xml"/>
        <!--
            实际开发中可能有多个映射文件,而其中sql标签的id相同时候,执行过程就会报错
            我们可以根据mapper映射文件中的namespace属性来区分,调用时候用如下方式
            namespace.id
        -->
        <!--
            <mapper resource="dao/mapper2.xml"/>
        -->
    </mappers>

</configuration>

2.mapper映射文件

<?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">
<!-- 文件头在解压的文件夹中mybatis-3.4.4.pdf文件中搜索mybatis-3-mapper.dtd即可得到 -->
<mapper namespace="model.SStudent">
    <!-- parameterType属性,框架会根据SQLSession中传递的参数检测到,所以我们一般不用指定 -->
    <insert id="insertStudentByList">
        insert into SStudent(sname,sage,score) values
        <!-- 这里面的collection必须写成list -->
        <foreach collection="list" separator="," item="stu">
            (#{stu.name},#{stu.age},#{stu.score})
        </foreach>
    </insert>

    <!-- 使用别名 -->
    <select id="selectById1" resultType="SStudent">
        select sid id,sname name,sage age,score from sstudent where sid = #{xxx}
    </select>

    <!-- 使用resultMap -->
    <select id="selectById2" resultMap="sStudentMapper">
        select sid,sname,sage,score from sstudent where sid = #{xxx}
    </select>

    <!--
        type:要映射的实体类
        id:resultMap标签的id,用于select标签中resultMap属性
    -->
    <resultMap id="sStudentMapper" type="SStudent">
        <id column="sid" property="id" />
        <result column="sname" property="name" />
        <result column="sage" property="age" />
    </resultMap>

</mapper>

3.实体类

package model;

/**
 * Created by carryLess on 2017/11/29.
 */
public class SStudent {
    private Integer id;
    private String name;
    private Integer age;
    private double score;

    public SStudent() {
    }

    public SStudent(String sname, Integer sage, double score) {
        this.name = sname;
        this.age = sage;
        this.score = score;
    }

    @Override
    public String toString() {
        return "SStudent{" +
                "id=" + id +
                ", sname=‘" + name + ‘\‘‘ +
                ", sage=" + age +
                ", score=" + score +
                ‘}‘;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getSname() {
        return name;
    }

    public void setSname(String sname) {
        this.name = sname;
    }

    public Integer getSage() {
        return age;
    }

    public void setSage(Integer sage) {
        this.age = sage;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }
}

 

4.dao接口与实现类

package dao;

import model.SStudent;

import java.util.List;
import java.util.Map;

/**
 * Created by carryLess on 2017/11/29.
 */
public interface IStudentDao {

    /**
     * 插入集合
     * @param studentList
     */
    void insertStudentByList(List<SStudent> studentList);

    /**
     * 根据id查询1
     * @param id
     * @return
     */
    SStudent selectById1(int id);

    /**
     * 根据id查询2
     * @param id
     * @return
     */
    SStudent selectById2(int id);
}

package dao;

import model.SStudent;
import org.apache.ibatis.session.SqlSession;
import utils.MyBatisUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Created by carryLess on 2017/11/29.
 */
public class StudentDaoImpl implements IStudentDao {
    private SqlSession sqlSession;


    @Override
    public void insertStudentByList(List<SStudent> studentList) {
        try {
            sqlSession = MyBatisUtils.getSqlSession();
            sqlSession.insert("insertStudentByList", studentList);
            sqlSession.commit();
        }finally {
            //关闭sqlSession
            if(sqlSession != null){
                sqlSession.close();
            }
        }
    }

    @Override
    public SStudent selectById1(int id) {
        SStudent sStudent;
        try {
            sqlSession = MyBatisUtils.getSqlSession();
            sStudent = sqlSession.selectOne("selectById1", id);
        } finally {
            if(sqlSession != null){
                sqlSession.close();
            }
        }
        return sStudent;
    }

    @Override
    public SStudent selectById2(int id) {
        SStudent sStudent;
        try {
            sqlSession = MyBatisUtils.getSqlSession();
            sStudent = sqlSession.selectOne("selectById2", id);
        } finally {
            if(sqlSession != null){
                sqlSession.close();
            }
        }
        return sStudent;
    }
}

5.工具类

package utils;

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 java.io.IOException;
import java.io.InputStream;

/**
 * Created by carryLess on 2017/11/30.
 */
public class MyBatisUtils {

    /*
    * SqlSession 由SqlSessionFactory对象创建,
    * 而SqlSessionFactory对象为重量级对象
    * 并且是线程安全的,所以我们将其设为单例
    * */
    private static SqlSessionFactory factory;

    /**
     * 私有化构造方法,避免该工具类在外部被实例化
     */
    private MyBatisUtils(){}

    /**
     * 获取 SqlSession
     * @return
     */
    public static SqlSession getSqlSession(){
        try {
            if(factory == null){
                //读取配置文件
                InputStream inputStream = Resources.getResourceAsStream("mybatis.xml");
                //创建工厂类
                factory = new SqlSessionFactoryBuilder().build(inputStream);
            }
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
        /*
        * factory.openSession(true);     创建一个有自动提交功能的SqlSession
        * factory.openSession(false);    创建一个没有自动提交功能的SqlSession,需要手动提交
        * factory.openSession();         同factory.openSession(false);
        */
        return factory.openSession();
    }
}

6.测试类

package test;

import dao.IStudentDao;
import dao.StudentDaoImpl;
import model.SStudent;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by carryLess on 2017/11/29.
 */
public class MyTest {

    private IStudentDao dao;

    @Before
    public void initDao(){
        dao = new StudentDaoImpl();
    }

    @Test
    public void testInsertList(){
        List<SStudent> sStudentList = new ArrayList<SStudent>();
        for(int i = 11;i<20;i++){
            SStudent sStudent = new SStudent();
            sStudent.setSname("zhangs-"+i);
            sStudent.setSage(25+i);
            sStudent.setScore(90);
            sStudentList.add(sStudent);
        }
        dao.insertStudentByList(sStudentList);
    }

    @Test
    public void testSelectById(){
        SStudent sStudent = dao.selectById2(18);
        System.out.println(sStudent);
    }


}