Spring Boot MyBatis 纯注解

引入依赖项

在 pom.xml 文件中引入 mybatis-spring-boot-starter 的依赖：

<!-- mysql驱动 -->
<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.22</version>
</dependency>
<!-- mybatis依赖 -->
<dependency>
  <groupId>org.mybatis.spring.boot</groupId>
  <artifactId>mybatis-spring-boot-starter</artifactId>
  <version>2.1.3</version>
</dependency>

配置 MySQL 连接数据

在 application.yml 文件中配置数据库连接：

# MySQL连接配置
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://172.30.88.71:3306/test?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: root

Mapper 配置

方式一：【推荐】在启动类上添加包扫描注解 @MapperScan(“com.example.mapper”)

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

方式二：在每个 Mapper 类上面添加 @Mapper 注解

Mapper 编写

官方文档对注解功能的说明：https://mybatis.org/mybatis-3/zh/java-api.html

User 实体类：

@Data
@Builder
public class User implements Serializable {
    private static final long serialVersionUID = -1602774207630314992L;
    private Integer id;
    private String username;
    private String password;
}

t_user 用户表 sql：

CREATE TABLE `t_user` (
  `id` int NOT NULL AUTO_INCREMENT,
  `username` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

增删改查示例：

// mapper
public interface UserMapper {
    @Select("select * from t_user where id=#{id}")
    @Results({
            @Result(property = "id", column = "id", javaType = Integer.class),
            @Result(property = "username", column = "username", javaType = String.class),
            @Result(property = "password", column = "password", javaType = String.class)
    })
    User selectById(Integer id);
    @Select("select * from t_user limit #{limit} offset #{offset}")
    List<User> selectAll(@Param("limit") int limit ,@Param("offset") int offset);
    @Insert("insert into t_user (id,username,password) values (#{id},#{username},#{password})")
    @SelectKey(statement="select last_insert_id()", keyProperty="id", before=false, resultType=int.class)
    int insert(User user);
    @Update("update t_user set username=#{username},password=#{password} where id=#{id}")
    int update(User user);
    @Delete("delete from t_user where id=#{tid}")
    int delete(@Param("tid") int id);
}

测试：

@SpringBootTest
@RunWith(SpringRunner.class)
public class ApplicationTest {
    @Resource
    private UserMapper userMapper;
    // 查
    @Test
    public void test() {
        User user = userMapper.selectById(1);
        System.out.println(user);
    }
    // 查询全部
    @Test
    public void testSelectAll() {
        List<User> users = userMapper.selectAll(2, 2);
        users.forEach(System.out::println);
    }
    // 增
    @Test
    public void testInsert() {
        User user = User.builder().username("张三").password("dfsfknl").build();
        int i = userMapper.insert(user);
        System.out.println(i);
        System.out.println(user);
    }
    // 更新
    @Test
    public void testUpdate() {
        User user = User.builder().username("张三").password("dfsfknl").build();
        int i = userMapper.update(user);
        System.out.println(i);
    }
    // 删除
    @Test
    public void testDelete() {
        int i = userMapper.delete(2);
        System.out.println(i);
    }
}