notes_estom/Spring/Springboot/09 MyBatis.md

对象关系映射模型Hibernate。用来实现非常轻量级的对象的封装。将对象与数据库建立映射关系。实现增删查改。 MyBatis与Hibernate非常相似。对象关系映射模型ORG。java对象与关系数据库映射的模型。

1 配置MyBatis

在pom.xml中添加MyBatis依赖

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

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

配置数据库连接

在application.properties中配置mysql的链接配置

spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

创建关系数据表

CREATE TABLE `User` (
  `id` bigint NOT NULL AUTO_INCREMENT,
  `name` varchar(100) COLLATE utf8mb4_general_ci DEFAULT NULL,
  `age` int DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci

创建数据表的java对象

@Data
@NoArgsConstructor
public class User {

    private Long id;

    private String name;
    private Integer age;

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

创建数据表的操作接口

@Mapper
public interface UserMapper {

    @Select("SELECT * FROM USER WHERE NAME = #{name}")
    User findByName(@Param("name") String name);

    @Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
    int insert(@Param("name") String name, @Param("age") Integer age);

}

2 MyBatis参数传递

使用@Param参数传递

@Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
int insert(@Param("name") String name, @Param("age") Integer age);

使用map 传递参数

@Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER})")
int insertByMap(Map<String, Object> map);
//调用
Map<String, Object> map = new HashMap<>();
map.put("name", "CCC");
map.put("age", 40);
userMapper.insertByMap(map);

使用普通java对象

@Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
int insertByUser(User user);

3 增删查改操作

public interface UserMapper {

    @Select("SELECT * FROM user WHERE name = #{name}")
    User findByName(@Param("name") String name);

    @Insert("INSERT INTO user(name, age) VALUES(#{name}, #{age})")
    int insert(@Param("name") String name, @Param("age") Integer age);

    @Update("UPDATE user SET age=#{age} WHERE name=#{name}")
    void update(User user);

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

对增删查改的调用

@Transactional
@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTests {

	@Autowired
	private UserMapper userMapper;

	@Test
	@Rollback
	public void testUserMapper() throws Exception {
		// insert一条数据，并select出来验证
		userMapper.insert("AAA", 20);
		User u = userMapper.findByName("AAA");
		Assert.assertEquals(20, u.getAge().intValue());
		// update一条数据，并select出来验证
		u.setAge(30);
		userMapper.update(u);
		u = userMapper.findByName("AAA");
		Assert.assertEquals(30, u.getAge().intValue());
		// 删除这条数据，并select验证
		userMapper.delete(u.getId());
		u = userMapper.findByName("AAA");
		Assert.assertEquals(null, u);
	}
}

4 使用MyBatis的XML方式

在应用主类中增加mapper的扫描包配置：

@MapperScan("com.didispace.chapter36.mapper")
@SpringBootApplication
public class Chapter36Application {

	public static void main(String[] args) {
		SpringApplication.run(Chapter36Application.class, args);
	}

}

Mapper包下创建User表

public interface UserMapper {

    User findByName(@Param("name") String name);

    int insert(@Param("name") String name, @Param("age") Integer age);

}

在配置文件中通过mybatis.mapper-locations参数指定xml配置的位置

mybatis.mapper-locations=classpath:mapper/*.xml

xml配置目录下创建User表的mapper配置

<?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.didispace.chapter36.mapper.UserMapper">
    <select id="findByName" resultType="com.didispace.chapter36.entity.User">
        SELECT * FROM USER WHERE NAME = #{name}
    </select>

    <insert id="insert">
        INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})
    </insert>
</mapper>

对xml方式进行调用

@Slf4j
@RunWith(SpringRunner.class)
@SpringBootTest
@Transactional
public class Chapter36ApplicationTests {

    @Autowired
    private UserMapper userMapper;

    @Test
    @Rollback
    public void test() throws Exception {
        userMapper.insert("AAA", 20);
        User u = userMapper.findByName("AAA");
        Assert.assertEquals(20, u.getAge().intValue());
    }

}