SpringBoot Mybatis 入门

Mybatis for Java API官方文档：http://www.mybatis.org/mybatis-3/zh/java-api.html

Mybatis语法介绍

@Select 查询，所有的查询均使用这个
@Insert 插入，直接传入实体类会自动解析属性到对应的值
@Update 修改，也可以直接传入对象
@Delete 删除

@Result 修饰返回的结果集，关联实体类属性和数据库字段一一对应，如果实体类属性和数据库属性名保持一致，就不需要这个属性来修饰。

这里需要注意，使用#符号和$符号的不同：

// This example creates a prepared statement, something like select * from teacher where name = ?;
@Select("Select * from teacher where name = #{name}")
Teacher selectTeachForGivenName(@Param("name") String name);

// This example creates n inlined statement, something like select * from teacher where name = 'someName';
@Select("Select * from teacher where name = '${name}'")
Teacher selectTeachForGivenName(@Param("name") String name);

使用步骤

1、在Maven配置文件中，添加mybatis和mysql依赖

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.3.2</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

2、application.properties添加数据库配置

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://172.16.65.200/hibernate?characterEncoding=UTF8
spring.datasource.username=root
spring.datasource.password=123456
mybatis.type-aliases-package=com.vmware.SpringMVC.domain  // Mybatis Mapper接口类的路径

Springboot会自动加载spring.datasource.*相关配置，数据源就会自动注入到sqlSessionFactory中，sqlSessionFactory会自动注入到Mapper中，对了你一切都不用管了。

3、编写Mapper接口类

public interface UserMapper {

    @Select("SELECT * FROM users")
    @Results({
        @Result(property = "userSex",  column = "user_sex", javaType = UserSexEnum.class),
        @Result(property = "nickName", column = "nick_name")
    })
    List<UserEntity> getAll();

    @Select("SELECT * FROM users WHERE id = #{id}")
    @Results({
        @Result(property = "userSex",  column = "user_sex", javaType = UserSexEnum.class),
        @Result(property = "nickName", column = "nick_name")
    })
    UserEntity getOne(Long id);

    @Insert("INSERT INTO users(userName,passWord,user_sex) VALUES(#{userName}, #{passWord}, #{userSex})")
    void insert(UserEntity user);

    @Update("UPDATE users SET userName=#{userName},nick_name=#{nickName} WHERE id =#{id}")
    void update(UserEntity user);

    @Delete("DELETE FROM users WHERE id =#{id}")
    void delete(Long id);

4、在Service业务逻辑层去调用Mapper接口

// 业务逻辑层调用Mapper
@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public List<User> getAll(){
        return userMapper.getAll();
    }
}

// Controller调用Service
@RestController
@RequestMapping("user")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/all")
    public List<User> getAll(){
        return userService.getAll();
    }
}

5、在启动类中添加对Mapper包扫描@MapperScan()

/**
 * @MapperScan() 表示扫描MyBatis的Mapper接口所在的包，找出所有加了@Mapper或@Repository注解的接口。
 */
@SpringBootApplication
@MapperScan("com.vmware.SpringMVC.domain")
public class SpringMvcApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringMvcApplication.class, args);
    }
}

参考资料：

http://412887952-qq-com.iteye.com/blog/2391924

https://blog.csdn.net/didi7696/article/details/80117238 

https://cloud.tencent.com/developer/article/1347912