IDEA中mybits的使用

1 使用mybits

https://mybatis.p2hp.com/getting-started.html

1. 创建实体类

public class User {
    private Long id;
    private String name;
    private Integer age;

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

2. 创建 Mapper 接口

import java.util.List;

public interface UserMapper {
    List<User> findAll();

    User findById(Long id);
}

3. 编写 Mapper XML
文件路径一般是：src/main/resources/mapper/UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.teemo.mybatis.mapper.UserMapper">

    <select id="findAll" resultType="com.teemo.pojo.User">
        SELECT id, name, age
        FROM user
    </select>

    <select id="findById" parameterType="long" resultType="com.teemo.pojo.User">
        SELECT id, name, age
        FROM user
        WHERE id = #{id}
    </select>

</mapper>

这里要注意：
要和你的 UserMapper 接口对应。如果有包名，就写完整包名，比如：

<mapper namespace="com.teemo.mapper.UserMapper">

3. 编写 MyBatis 配置文件
   文件路径：src/main/resources/mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    <environments default="dev">
        <environment id="dev">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test?serverTimezone=Asia/Shanghai"/>
                <property name="username" value="root"/>
                <property name="password" value="你的数据库密码"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>

</configuration>

4. 编写测试代码

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.InputStream;
import java.util.List;

public class Main {
    public static void main(String[] args) throws Exception {
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");

        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(inputStream);

        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            List<User> users = userMapper.findAll();

            for (User user : users) {
                System.out.println(user.getId() + " " + user.getName() + " " + user.getAge());
            }
        }
    }
}

5. userMap 可以添加映射关系
   

2 mybits generator

使用MyBatis Generator插件：只需配置数据库连接信息，指定生成位置和规则，即可自动生成PO类。

步骤1：新建 generatorConfig.xml
src/main/resources 目录下创建 generatorConfig.xml 文件，配置 MBG 的基本参数：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">

<generatorConfiguration>
    <!-- 数据库驱动路径（可选，若已通过 Maven 引入驱动则无需指定） -->
    <!-- <classPathEntry location="D:/maven/repository/mysql/mysql-connector-java/8.0.33/mysql-connector-java-8.0.33.jar"/> -->

    <context id="DB2Tables" targetRuntime="MyBatis3">
        <!-- 自动识别数据库关键字，默认 false -->
        <property name="autoDelimitKeywords" value="true"/>
        <!-- 生成的 Java 文件的编码 -->
        <property name="javaFileEncoding" value="UTF-8"/>
        
        <!-- 注释生成器配置 -->
        <commentGenerator>
            <property name="suppressDate" value="true"/> <!-- 不生成日期 -->
            <property name="suppressAllComments" value="true"/> <!-- 不生成注释 -->
        </commentGenerator>

        <!-- 数据库连接配置 -->
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/your_database"
                        userId="root"
                        password="your_password">
            <!-- 针对 MySQL 的时区问题配置 -->
            <property name="nullCatalogMeansCurrent" value="true"/>
        </jdbcConnection>

        <!-- Java 类型处理器 -->
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>

        <!-- 生成实体类的配置 -->
        <javaModelGenerator targetPackage="com.example.entity"
                            targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
            <property name="trimStrings" value="true"/>
        </javaModelGenerator>

        <!-- 生成Mapper XML 映射文件的配置 -->
        <sqlMapGenerator targetPackage="mapper"
                         targetProject="src/main/resources">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>

        <!-- 生成 Mapper 接口的配置 -->
        <javaClientGenerator type="XMLMAPPER"
                             targetPackage="com.example.mapper"
                             targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>

        <!-- 指定要生成代码的表（可配置多个 table 节点） -->
        <table tableName="user" domainObjectName="User" enableCountByExample="false"
               enableUpdateByExample="false" enableDeleteByExample="false"
               enableSelectByExample="false" selectByExampleQueryId="false">
            <!-- 列映射配置（可选） -->
            <!-- <columnOverride column="id" property="id" javaType="java.lang.Integer"/> -->
        </table>
        
        <!-- 可添加更多表配置... -->
    </context>
</generatorConfiguration>

步骤2：新建 generatorConfig.xml
接通过 Maven 插件运行（推荐）
无需手动配置 Run Configuration，通过 IDEA 的 Maven 面板即可快速运行：

• 在 IDEA 右侧打开 Maven 面板（若未显示，可通过 View -> Tool Windows -> Maven 调出）；
• 展开当前项目的 Plugins -> mybatis-generator；
• 双击 mybatis-generator:generate 即可执行代码生成：

生成的文件将出现在配置指定的目录下
参考：
https://blog.youkuaiyun.com/2302_79926174/article/details/149451473