整合MyBatis

• pom.xml添加依赖

<dependencies>
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.1.1</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.11</version>
    </dependency>
</dependencies>

注：此处不引入spring-boot-starter-jdbc依赖是由于mybatis-spring-boot-starter中已经包含了此依赖。MySQL版本不对可能会报错。

• application.properties配置mysql连接

spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

使用MyBatis

• 创建映射对象User

public class User {

    private Long id;
    private String name;
    private Integer age;

    public User() {}

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

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

    public Long getId() { return id; }

    public void setId(Long id) { this.id = id; }

    public String getName() { return name; }

    public void setName(String name) { this.name = name; }

    public Integer getAge() { return age; }

    public void setAge(Integer age) { this.age = age; }

}

• 创建User映射的操作UserMapper，实现插入和查询操作

@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);
}

• 单元测试：测试结束回滚数据，保证测试单元每次运行的数据环境独立

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
public class ApplicationTests {

    @Autowired
    private UserMapper userMapper;

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

MyBatis注解配置详解

• 使用@Param传参数

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

@Param中定义的name对应了SQL中的#{name}，age对应了SQL中的#{age}。

• 通过Map对象来昨晚传递参数的容器

@Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name,jdbcType=VARCHAR}, #{age,jdbcType=INTEGER})")
int insertByMap(Map<String, Object> map);

示例：

Map<String, Object> map = new HashMap<>();
map.put("name", "CCC");
map.put("age", 40);
userMapper.insertByMap(map);

• 使用普通的Java对象来作为查询条件的传参

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

#{name}、#{age}分别对应User对象中的name和age属性。

增删改查

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);
}

• 测试：

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class)
@Transactional
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);
    }
}

• 查，返回结果的绑定，使用@Results和@Result注解来进行绑定

@Results({
    @Result(property = "name", column = "name"),
    @Result(property = "age", column = "age")
})
@Select("SELECT name, age FROM user")
List<User> findAll();

注：@Result中的property属性对应User对象中的成员名，column对应SELECT出的字段名。
在该配置中故意没有查出id属性，只对User对应中的name和age对象做了映射配置，这样可以通过下面的单元测试来验证查出的id为null，而其他属性不为null：

@Test
@Rollback
public void testUserMapper() throws Exception {
    List<User> userList = userMapper.findAll();
    for(User user : userList) {
        Assert.assertEquals(null, user.getId());
        Assert.assertNotEquals(null, user.getName());
    }
}