MyBatis概述

MyBatis是一个优秀的持久层框架，它支持定制化SQL、存储过程以及高级映射。MyBatis避免了几乎所有的JDBC代码和手动设置参数以及获取结果集的过程。

核心特点

优势：

SQL语句与Java代码分离，便于维护
支持动态SQL，灵活性高
提供了强大的映射功能
与Spring框架集成良好
学习成本相对较低

与其他框架对比：

相比Hibernate：更轻量级，SQL可控性更强
相比JDBC：减少了大量样板代码
相比JPA：更适合复杂查询和性能优化

MyBatis核心组件

1. SqlSessionFactory

// 创建SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

2. SqlSession

// 获取SqlSession
SqlSession session = sqlSessionFactory.openSession();
try {// 执行操作UserMapper mapper = session.getMapper(UserMapper.class);User user = mapper.selectUser(1);
} finally {session.close();
}

3. Mapper接口

public interface UserMapper {User selectUser(int id);List<User> selectAllUsers();void insertUser(User user);void updateUser(User user);void deleteUser(int id);
}

4. XML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">
<mapper namespace="com.example.mapper.UserMapper"><select id="selectUser" parameterType="int" resultType="User">SELECT * FROM users WHERE id = #{id}</select><insert id="insertUser" parameterType="User">INSERT INTO users (name, email) VALUES (#{name}, #{email})</insert>
</mapper>

IDEA中的MyBatis开发

1. 项目创建与依赖配置

Maven依赖：

<dependencies><!-- MyBatis核心依赖 --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.13</version></dependency><!-- 数据库驱动 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.33</version></dependency><!-- Spring Boot集成（可选） --><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>3.0.2</version></dependency>
</dependencies>

2. IDEA插件推荐

MyBatis相关插件：

MyBatis Log Plugin：日志格式化显示
MyBatis Mapper Generator：代码生成
Free MyBatis Plugin：XML与Mapper跳转
MyBatis Plus：增强功能支持

3. 配置文件设置

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><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/mybatis_db"/><property name="username" value="root"/><property name="password" value="password"/></dataSource></environment></environments><mappers><mapper resource="mapper/UserMapper.xml"/></mappers>
</configuration>

4. 实体类设计

public class User {private Integer id;private String name;private String email;private Date createTime;// 构造方法、getter、setter省略
}

5. Mapper接口与XML映射

UserMapper.java：

@Mapper
public interface UserMapper {@Select("SELECT * FROM users WHERE id = #{id}")User selectById(Integer id);List<User> selectAll();@Insert("INSERT INTO users(name, email) VALUES(#{name}, #{email})")@Options(useGeneratedKeys = true, keyProperty = "id")void insert(User user);void update(User user);@Delete("DELETE FROM users WHERE id = #{id}")void deleteById(Integer id);
}

UserMapper.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">
<mapper namespace="com.example.mapper.UserMapper"><resultMap id="userResultMap" type="User"><id property="id" column="id"/><result property="name" column="name"/><result property="email" column="email"/><result property="createTime" column="create_time"/></resultMap><select id="selectAll" resultMap="userResultMap">SELECT id, name, email, create_time FROM users</select><update id="update" parameterType="User">UPDATE users SET name = #{name},email = #{email}WHERE id = #{id}</update><!-- 动态SQL示例 --><select id="selectByCondition" parameterType="User" resultMap="userResultMap">SELECT * FROM users<where><if test="name != null and name != ''">AND name LIKE CONCAT('%', #{name}, '%')</if><if test="email != null and email != ''">AND email = #{email}</if></where></select>
</mapper>

动态SQL详解

1. if标签

<select id="selectByCondition" parameterType="User" resultType="User">SELECT * FROM users<where><if test="name != null and name != ''">AND name = #{name}</if><if test="email != null">AND email = #{email}</if></where>
</select>

2. choose、when、otherwise

<select id="selectByIdOrName" parameterType="User" resultType="User">SELECT * FROM users<where><choose><when test="id != null">id = #{id}</when><when test="name != null and name != ''">name = #{name}</when><otherwise>1 = 1</otherwise></choose></where>
</select>

3. foreach标签

<select id="selectByIds" parameterType="list" resultType="User">SELECT * FROM users WHERE id IN<foreach collection="list" item="id" open="(" close=")" separator=",">#{id}</foreach>
</select>

Spring Boot集成

1. 配置文件

# application.yml
mybatis:mapper-locations: classpath:mapper/*.xmltype-aliases-package: com.example.entityconfiguration:map-underscore-to-camel-case: truespring:datasource:url: jdbc:mysql://localhost:3306/mybatis_dbusername: rootpassword: passworddriver-class-name: com.mysql.cj.jdbc.Driver

2. 主启动类

@SpringBootApplication
@MapperScan("com.example.mapper")
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}
}

3. Service层实现

@Service
public class UserService {@Autowiredprivate UserMapper userMapper;public User getUserById(Integer id) {return userMapper.selectById(id);}public List<User> getAllUsers() {return userMapper.selectAll();}@Transactionalpublic void saveUser(User user) {userMapper.insert(user);}
}

IDEA开发技巧

1. 代码生成器使用

MyBatis Generator配置：

<generatorConfiguration><context id="MySQLTables" targetRuntime="MyBatis3"><jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"connectionURL="jdbc:mysql://localhost:3306/mybatis_db"userId="root"password="password"/><javaModelGenerator targetPackage="com.example.entity" targetProject="src/main/java"/><sqlMapGenerator targetPackage="mapper" targetProject="src/main/resources"/><javaClientGenerator type="XMLMAPPER" targetPackage="com.example.mapper" targetProject="src/main/java"/><table tableName="users" domainObjectName="User"/></context>
</generatorConfiguration>