2023-10-25

mybatis基础

maven安装

mysql

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.29</version>
</dependency>

mybatis

<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>x.x.x</version>
</dependency>

配置文件

java

[类名]Mapper.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">
<!--接口路径-->
<mapper namespace="cn.sdadgz.dao.UserMapper">
    <!--显示全部-->
    <select id="getUserList" resultType="cn.sdadgz.pojo.User">
        select * from mybatis.user
    </select>
    <!--查询指定-->
    <select id="getUserById" parameterType="int" resultType="cn.sdadgz.pojo.User">
    	select * from mybatis.user where id = #{id}
    </select>
    <!--插入-->
    <insert id="addUser" parameterType="cn.sdadgz.pojo.User">
    	insert into mybatis.user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>
    <!--更新-->
    <update id="updateUser" parameterType="cn.sdadgz.pojo.User">
    	update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id}
    </update>
    <!--删除-->
    <delete id="deleteUser" parameter="int">
    	delete from mybatis.user where id = #{id}
    </delete>
</mapper>

id 调用时名字
resultType 返回值类型
parameterType 参数类型

resultMap

result

1657182916658

association（对象）

property 对象名
column 数据库名 向子查询传参用这个 column=”id = user_id”
javaType 类名
嵌套增删改查例：select

例：association（子查询） column传参

1657294027376

例：association-2

1657294812642

collection

ofType

例：collection

1657297461218

例：collection-2

1657298641599

utils工具类

package cn.sdadgz.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;

public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

resources

mybatis-config.xml配置文件

settings
1. 配置_MyBatis中文网
mappers
1. mapper
  1. resource 指定xml
  2. class 指定class，接口必须和xml同名
  3. package 自动扫描，接口必须和xml同名

<?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>

    <!--里面可以放property定义值-->
    <properties resource="db.properties"/>

    <!--起别名-->
    <typeAliases>
        <!--指定类起别名-->
        <typeAlias type="cn.sdadgz.pojo.User" alias="User"/>
        <!--自动扫描默认首字母小写，再类前加注解@Alias("[别名]")自定义-->
        <package name="cn.sdadgz.pojo"/>
    </typeAliases>
    
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="cn/sdadgz/dao/UserMapper.xml"/>
    </mappers>
</configuration>

db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://49.232.139.28:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=[密码]

test

import cn.sdadgz.dao.UserDao;
import cn.sdadgz.pojo.User;
import cn.sdadgz.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;


public class UserDaoTest {

    @Test
    public void test(){
        // 调用工具类
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        // 接口mapper
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        // 方法
        List<User> userList = userMapper.getUserList();

        for (User user : userList){
            System.out.println(user);
        }

        sqlSession.close();
    }
}