Mybatis之简单注解

Mybatis使用注解实现主键自增长：
oracle：
@SelectKey(statement="select my_seq.nextval from dual",resultType=int.class,keyProperty="id",before=true)
statement是生成id语句，resultType是语句返回类型，keyProperty是填入id列，before是先写入对象，再写入表
mysql：
@Options(useGeneratedKeys=true,keyProperty="id",keyColumn="id")

@Results：结果映射
@Results注解和映射器XML配置文件元素<resultMap> 对应。

@Select("select id as pid,name,age from person")
@Results({
@Result(id=true,property="id",column="pid"),
@Result(property="name",column="name"),
@Result(property="age",column="age")
})
public List<Person> selectAllPerson_ResultMap();

 

resultMap可以重用，@Results不可以重用。
解决方法：
创建一个映射器Mapper配置文件，然后配置<resultMap>元素，然后使用 @ResultMap注解引用此<resultMap>
@ResultMap(【命名空间名】.【ResultMap_id】)
@One注解：
一对一关联查询

@Select("select addr_id as addrId, street, city, state, zip, country from addresses where addr_id=#{id}") 
Address findAddressById(int id);

@Select("select * from students where stud_id=#{studId} ") 
@Results( 
{ 
@Result(id = true, column = "stud_id", property = "studId"), 
@Result(column = "name", property = "name"), 
@Result(column = "email", property = "email"), 
@Result(property = "address", column = "addr_id", 
one = @One(select = "com.briup.mapper.StudentMapper.findAddressById")) 
}) 
Student selectStudentWithAddress(int studId);

 

@Many注解：
一对多关联查询

@Select("select addr_id as addrId, street, city, state, zip, 
country from addresses where addr_id=#{id}") 
Address findAddressById(int id);

@Select("select * from courses where tutor_id=#{tutorId}") 
@Results( 
{ 
@Result(id = true, column = "course_id", property = "courseId"), 
@Result(column = "name", property = "name"), 
@Result(column = "description", property = "description"), 
@Result(column = "start_date" property = "startDate"), 
@Result(column = "end_date" property = "endDate") 
}) 
List<Course> findCoursesByTutorId(int tutorId);

@Select("SELECT tutor_id, name as tutor_name, email, addr_id 
FROM tutors where tutor_id=#{tutorId}") 
@Results( 
{ 
@Result(id = true, column = "tutor_id", property = "tutorId"), 
@Result(column = "tutor_name", property = "name"), 
@Result(column = "email", property = "email"), 
@Result(property = "address", column = "addr_id", 
one = @One(select = "com.briup.mappers.Tutor Mapper.findAddressById")), 
@Result(property = "courses", column = "tutor_id", 
many = @Many(select = "com.briup.mappers.Tutor Mapper.findCoursesByTutorId")) 
}) 
Tutor findTutorById(int tutorId);

 

@mapper注解:
把mapper这个DAO交给spring去管理
不在写mapper的映射文件