mybatis:注解开发

说明

在mybatis中使用注解开发可以简化mapper.xml文件的配置

使用方法

1. 编写操作数据库的接口，写方法
2. 在这些方法上面直接写注解

代码实例

public interface IBossMapper {
	//1.查询所有的boss
	@Select("select * from boss")
	public List<Boss> allBoss();
	
	//2.以bid查询boss
	@Select("select * from boss where bid=#{bid}")
	public Boss selByBid(int sid);
	
	//3.插入一个boss
	@Insert("insert into boss values(#{bid},#{bname})")
	public void insert(Boss boss);
	
	//4.以bid删除boss
	@Delete("delete from boss where bid=#{bid}")
	public void deleteByBid(int bid);
	
	//5.以bid更新boss的bname
	@Update("update boss set bname=#{bname} where bid=#{bid}")
	public void updateBname(Boss boss);
	
	//------------------------------注解实现一对一、一对多等关系---------------------------------
	//一对一：以丈夫id找到丈夫及妻子
	@Select("select * from husband where hid=#{hid}")    //hid hname wid(wife)
	//相当于resultMap
	@Results({
		//主键列
		@Result(id=true,column="hid",property="hid"),
		@Result(column="hname",property="hname"),
		@Result(column="wid",property="wife",one=@One(
			select = "selectWifeByWid"
		))
	})
	public Husband selectHusbandByHid(int hid);
	
	//以wid找到wife
	@Select("select * from wife where wid=#{wid}")
	public Wife selectWifeByWid(int wid);
	
	//一对多
	//以班级id，找到该班级及所有的学生
	@Select("select * from clazz")   //cid cname
	@Results({
		@Result(id=true,column="cid",property="cid"),
		@Result(column="cname",property="cname"),
		@Result(column="cid",property="students",many=@Many(
			select="selectStudentsByCid",
			fetchType=FetchType.LAZY		//指定获取的类型为懒加载
		))
	})
	public List<Clazz> allClazz();
	
	//通过cid找到学生
	@Select("select * from student where cid=#{cid}")
	public List<Student> selectStudentsByCid(int cid);
	
	
	//多对一：查询出所有的学生及学生所在的班级
	
	@Select("select * from student")
	@Results({
		@Result(id=true,column="sid",property="sid"),
		@Result(column="sname",property="sname"),
		@Result(column="cid",property="clazz",one=@One(
				select="selectClazzByCid"
		))
	})
	public List<Student> allStudent();
	
	@Select("select * from clazz where cid=#{cid}")   //cid cname 
	public Clazz selectClazzByCid(int cid);
	
	
	//多对多:以bid找到boss及其下的company
	@Select("select * from boss where bid=#{bid}")
	@Results({
		@Result(id=true,column="bid",property="bid"),
		@Result(column="bname",property="bname"),
		@Result(column="bid",property="companies",many=@Many(
				select="seleceCompaniesByBid"
		))
	})
	public Boss selectBossByBid(int bid);
	
	@Select("select * from boss_company bc,company c where bc.bid=#{bid} and bc.cid=c.cid")
	@Results({
		@Result(id=true,column="cid",property="cid"),
		@Result(column="cname",property="cname")
	})
	public List<Company> seleceCompaniesByBid(int bid);
}

使用：

public class Base {
	public static void main(String[] args) {
		SqlSession session = MyBatisUtil.getSession();
		IBossMapper mapper = session.getMapper(IBossMapper.class);
		System.out.println(mapper.selectBossByBid(1001));
		session.commit();
	}
}