Mybatis 入门与配置

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MyBatis 是一款优秀的持久层框架，支持自定义 SQL、存储过程和高级映射。它避免了几乎所有的 JDBC 代码和手动设置参数。

核心组件

组件	说明
SqlSessionFactory	创建 SqlSession 的工厂
SqlSession	数据库会话，执行 SQL
Mapper	映射接口，定义数据库操作
XML 映射文件	SQL 定义和结果映射

配置 MyBatis

<!-- 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>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/demo"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

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

快速开始

public class MyBatisDemo {
    public static void main(String[] args) throws IOException {
        // 获取 SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 获取 SqlSession
        try (SqlSession session = sqlSessionFactory.openSession(true)) {
            User user = session.selectOne("com.example.mapper.UserMapper.selectById", 1L);
            System.out.println(user);
        }
    }
}

使用 Mapper 接口

// Mapper 接口
public interface UserMapper {
    User selectById(Long id);
    List<User> selectAll();
    int insert(User user);
    int update(User user);
    int deleteById(Long id);
}

// 使用 Mapper（推荐）
try (SqlSession session = sqlSessionFactory.openSession(true)) {
    UserMapper mapper = session.getMapper(UserMapper.class);
    User user = mapper.selectById(1L);
}