文章目录

快速搭建 MyBatis

  1. Maven

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

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.8</version>
        </dependency>
　　　　　<!--日志约束-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version> RELEASE</version>
        </dependency>

  2. mybatis-config.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">
<configuration>
    <!--配置别名-->
    <typeAliases>
        <package name="com.sf.wj.domain"/>
    </typeAliases>
    <!--数据源配置-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/company?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    
    <!--资源引用-->
    <mappers>
        <mapper resource="mappers/UserMapper.xml"/>
    </mappers>

</configuration>

  3. 【测试类 - 部分】根据 xml 配置文件（全局配置文件） 创建一个 SqlSessionFactory 对象

    package com.sf.wj;

import com.sf.wj.domain.User;
import com.sf.wj.mapper.UserMapper;
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.IOException;
import java.io.InputStream;
import java.util.List;

public class UserTest {
    private UserMapper mapper;
    private SqlSession sqlSession;
    private InputStream inputStream;
    @Before
    public void setUp() throws IOException {
        String rusource = "mybatis-config.xml";
         inputStream = Resources.getResourceAsStream(rusource);
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //默认传入参数false，不自动提交
        sqlSession = factory.openSession(false); // 2、获取sqlSession实例，能直接执行已经映射的 sql 语句
        mapper = sqlSession.getMapper(UserMapper.class);
    }

  4. 创建 mapper 映射

    <?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.sf.wj.mapper.UserMapper"><!-- namespace：名称空间 -->
    <select id="queryById" parameterType="int" resultType="User"><!--id：唯一表示、resultType：返回值类型-->
        select * from user where id = #{id}<!--#{id}接口从传递过来的参数-->
    </select>

    <delete id="deleteById" parameterType="Integer" >
        delete from user where id = #{id}
    </delete>

    <select id="queryAll" resultType="User">
        select * from user
    </select>

    <update id="updateUser" parameterType="User">
        update user set username = #{username},password = #{password} where id=#{id}
    </update>

    <insert id="insertUser" parameterType="User">
        insert into user (id,username,password) values (#{id},#{username},#{password})
    </insert>
　　
　　<!--按多个id查找用户 foreach-->
　　<select id="queryByIds" resultType="User">
  　　  select * from user where id in
   　　 <foreach collection="array" open="(" close=")" separator="," item="id">
        #{id}
    　　</foreach>
　　</select>
</mapper>

  5. 创建 mapper 接口

    package com.sf.wj.mapper;

import com.sf.wj.domain.User;

import java.util.List;

public interface UserMapper {
    User queryById(int id);
    void deleteById(int id);
    List<User> queryAll();
    void  updateUser(User user);
    void insertUser(User user);
    List<User> queryByIds(int[] ids);
}

  6. 补完测试类

    package com.sf.wj;

import com.sf.wj.domain.User;
import com.sf.wj.mapper.UserMapper;
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.IOException;
import java.io.InputStream;
import java.util.List;

public class UserTest {
    private UserMapper mapper;
    private SqlSession sqlSession;
    private InputStream inputStream;
    @Before
    public void setUp() throws IOException {
        String rusource = "mybatis-config.xml";
         inputStream = Resources.getResourceAsStream(rusource);
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //默认传入参数false，不自动提交
        sqlSession = factory.openSession(false); // 2、获取sqlSession实例，能直接执行已经映射的 sql 语句
        mapper = sqlSession.getMapper(UserMapper.class);
    }

    @After
    public void commit(){
        try {
            sqlSession.commit();
            inputStream.close();
            sqlSession.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Test
    public void queryByIdTest(){
        User user = mapper.queryById(1);
        System.out.println(user);
    }
    @Test
    public void queryAllTest(){
        List<User> user = mapper.queryAll();
        System.out.println(user);
    }
    @Test
    public void deleteTest(){
        mapper.deleteById(1);
    }
    @Test
    public void updateTest(){
        User user=new User();
        user.setId(1);
        user.setPassword("qwert");
        user.setUsername("jg");
        mapper.updateUser(user);
    }

    @Test
    public void insertTest(){
        User user=new User();
        user.setId(3);
        user.setPassword("369");
        user.setUsername("zs");
        mapper.insertUser(user);
    }

　　//多个id查找
　　@Test
　　public void queryByIdsTest(){
   　　 List<User> list = mapper.queryByIds(new int[]{1, 2, 3});
   　　 System.out.println(list);
　　}
}

技术对比

# JDBC工具？Hibernate？

JDBC工具（Dbutils、jdbcTemplate…）缺点

  • sql语句在java 代码里面，硬编码，高耦合
  • 缺少整体的解决方案

Hibernate缺点

  • 无法优化 sql
  • 自定义 sql 需要学习 HQL （但框架旨在消除sql - 与宗旨矛盾）

# Mybatis

  • sql 与 java 编码分离
  • sql 开发人员控制

使用 Mybatis ， 只要掌握好 sql 语句

半自动

历史