MyBatis注解开发
MyBatis同时支持注解开发模式，在面对简单的配置时，注解开发可以明显的减轻开发难度
MyBatis注解类型
注解 | 作用 |
|---|---|
@Insert | 用于执行新增语句 |
@Update | 用于执行更新语句 |
@Delete | 用于执行删除语句 |
@Select | 用于执行查询语句 |
@Result | 用于实现结果集的封装 |
@Results | 与@Result一起使用，实现多个结果集的封装 |
@One | 实现一对一结果集的封装 |
@Many | 实现一对多或多对多的结果集的封装 |
基本使用步骤
直接在mapper接口类中使用注解
参数传入的是要执行的sql语句
代码语言：javascript复制public interface UserMapper {
@Select("select * from user")
public List<User> findAll();
@Insert("insert into user values (#{id},#{username},#{password})")
public void save(User user);
@Update("update user set username=#{username},password=#{password} where id=#{id}")
public void update(User user);
@Delete("delete from user where id=#{id}")
public void delete(Long id);
}在核心文件配置扫描器，扫描指定包下的注解
代码语言：javascript复制<!--加载映射关系-->
<mappers>
<!--加载映射关系：扫描注解-->
<package name="cn.ywrby.mapper"></package>
</mappers>一对一模型使用注解开发
通过@Results和@Result配置映射关系进行一对一模型的注解开发(column表示数据段名称，property表示类中属性值名称)
代码语言：javascript复制public interface OrderMapper {
@Results({
@Result(column = "oid",property = "id"),
@Result(column = "orderName",property = "orderName"),
@Result(column = "orderAmount",property = "orderAmount"),
@Result(column = "userId",property = "user.id"),
@Result(column = "username",property = "user.username"),
@Result(column = "password",property = "user.password")
})
@Select("select *,o.id oid from orders o ,user u where o.userId=u.id")
public List<Order> findAll();
}一对多/多对多模型使用注解开发
一对多模型或多对多模型使用注解开发需要分开查询，首先在用户查询方法中配置基本映射对象，配置orderList对象时需要指定javaType为集合类型，以及many属性利用@Many标签指定一对多模型查询使用的另一个表的方法
代码语言：javascript复制public interface UserMapper {
@Select("select * from user")
@Results({
@Result(column = "id",property = "id"),
@Result(column = "username",property = "username"),
@Result(column = "password",property = "password"),
@Result(
property = "orderList",
column = "id",
javaType = List.class,
many = @Many(select = "cn.ywrby.mapper.OrderMapper.findByUid")
)
})
public List<User> findAll();
}另一个表的查询方法，由于除了查询需要的uid，查询结果数据都是本表内的，所以不需要配置映射关系
代码语言：javascript复制public interface OrderMapper {
@Select("select * from orders where userId=#{uid}")
public List<Order> findByUid();
}测试用例
代码语言：javascript复制public class MyBatisTest {
private UserMapper mapper;
@Before
public void before() throws IOException {
InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
SqlSessionFactory factory=new SqlSessionFactoryBuilder().build(resourceAsStream);
SqlSession sqlSession = factory.openSession(true);
mapper = sqlSession.getMapper(UserMapper.class);
}
@Test
public void test(){
List<User> userList=mapper.findAll();
for(User user:userList){
System.out.println(user);
}
}
}
/*
User{id=1, username='Leslie', password='123', orderList=[Order{id=1, orderName='textbook', orderAmount=10, user=null}, Order{id=9, orderName='mathbook', orderAmount=16, user=null}]}
User{id=2, username='Jessica', password='123', orderList=[Order{id=2, orderName='mathbook', orderAmount=15, user=null}]}
User{id=4, username='lily', password='1234', orderList=[Order{id=3, orderName='writebook', orderAmount=6, user=null}]}
User{id=6, username='Kelly', password='1234', orderList=[Order{id=4, orderName='chinesebook', orderAmount=10, user=null}]}
User{id=7, username='Les', password='1234', orderList=[Order{id=5, orderName='textbook', orderAmount=10, user=null}]}
User{id=8, username='dshjihi', password='398', orderList=[Order{id=6, orderName='textbook', orderAmount=10, user=null}]}
User{id=9, username='Pixel', password='9999', orderList=[]}
*/
