五、hibernate中持久层操作（多表之间的关联关系操作，1对1，一对多，多对多、继承）

下面是全部都是双向关系的数据，所有数据的关系在https://blog.csdn.net/IT_CREATE/article/details/87370051有说

一、1对1关系：

（利用丈夫和妻子进行介绍，一个丈夫含有一个妻子，一个妻子含有一个丈夫）

HusbandBean类：

private Integer id;
private String husbandName;
private Integer age;
    
private WifeBean wife;

WifeBean类：

private Integer id;
private String wifeName;
private Integer age;
    
private HusbandBean hus;

 

持久层操作查询丈夫，得到分页数据：

1、利用hql语句进行查询

@Repository
public class HusbandDaoImpl implements IHusbandDao {

	private Session session;
	
	@Override
	public void findHusbandBeanByWifeAge2PageBean(PageBean page, Integer age) {
		// TODO Auto-generated method stub
		
		String hql = "select count(*) From HusbandBean as h left join h.wife as w where w.age >= :age";
		Query query = session.createQuery(hql);
		query.setInteger("age", age);
		
		long totalRows = (long) query.uniqueResult();
		List<?> datas = null;
		if(totalRows > 0) {
			hql = "From HusbandBean as h left join fetch h.wife as w where w.age >= :age";
			query = session.createQuery(hql);
			query.setInteger("age", age);
			query.setFirstResult(page.getIndex());
			query.setMaxResults(page.getRows());
			datas = query.list();
		}
		page.setTotalRows(totalRows);
		page.setData(datas);
	}

}

2、利用Criteria

@Repository
public class HusbandDaoImpl implements IHusbandDao {

	private Session session;
	
	@Override
	public void findHusbandBeanByWifeAge2PageBean(PageBean page, Integer age) {
		// TODO Auto-generated method stub
		Criteria criteria = session.createCriteria(HusbandBean.class);
		criteria.createAlias("wife", "w", JoinType.LEFT_OUTER_JOIN);
		if(age != null) {
			criteria.add(Restrictions.ge("w.age", age));
		}
		
		//加投影
		criteria.setProjection(Projections.rowCount());
		long totalRows = (long) criteria.uniqueResult();
		List<?> datas = null;
		if(totalRows > 0) {
			//去掉投影
			criteria.setProjection(null);
			criteria.setFirstResult(page.getIndex());
			criteria.setMaxResults(page.getRows());
			criteria.setResultTransformer(Criteria.ROOT_ENTITY);//这句话的作用  === HQL中编写的fetch
			datas = criteria.list();
		}
		
		page.setTotalRows(totalRows);
		page.setData(datas);
	}

}

 

二、一对多的关系

这里我用学生和老师进行举例，一个老师对应对个学生，一个学生对应一个老师

TeacherBean类：

private Integer id;
private String teacherName;
private Integer age;
    
private Set<StudentBean> stus;

StudentBean类：

private Integer id;
private String stuName;
private Integer age;
    
private TeacherBean teacher;

 

操作老师的查询方法（查询学生名字查出对应的老师）：

1、利用hql

@Repository
public class TeacherDaoImpl implements ITeacherDao {
	
	private Session session;
	
	@Override
	public List<?> findTeacherBeanByStudentName(String stuName) {
		// TODO Auto-generated method stub
		String hql = "select DISTINCT(t) From TeacherBean as t left join fetch t.stus as s where s.stuName like concat(:stuName,'%')";
		Query query = session.createQuery(hql);
		query.setString("stuName", stuName);
		return query.list();
		
	}
	
}

2、利用Criteria

@Repository
public class TeacherDaoImpl implements ITeacherDao {
	
	private Session session;

	@Override
	public List<?> findTeacherBeanByStudentName(String stuName) {
		// TODO Auto-generated method stub
	
		Criteria criteria = session.createCriteria(TeacherBean.class);
		criteria.createAlias("stus", "s",JoinType.LEFT_OUTER_JOIN);
		if(!StringUtils.isEmpty(stuName)) {
			criteria.add(Restrictions.like("s.stuName", stuName, MatchMode.START));
		}
		
		//去重复
		criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
		return criteria.list();
	}

}

 

操作学生：（通过查询老师名字，得到所有学生的分页数据）

1、利用hql

@Repository
public class StudentDaoImpl implements IStudentDao {

	private Session session;

	@Override
	public void findStudentBeanByTeacherName2PageBean(PageBean page, String teacherName) {
		// TODO Auto-generated method stub		
		
		String hql = "select count(*) From StudentBean as s left join s.teacher as t where t.teacherName like concat(:teacherName,'%')";
		Query query = session.createQuery(hql);
		query.setString("teacherName", teacherName);
		long totalRows = (long) query.uniqueResult();
		List<?> datas = null;
		if(totalRows > 0) {
			hql = "From StudentBean as s left join fetch s.teacher as t where t.teacherName like concat(:teacherName,'%')";
			query = session.createQuery(hql);
			query.setString("teacherName", teacherName);
			query.setFirstResult(page.getIndex());
			query.setMaxResults(page.getRows());
			datas = query.list();
		}
		page.setTotalRows(totalRows);
		page.setData(datas);	
	}

}

2、利用Criteria

@Repository
public class StudentDaoImpl implements IStudentDao {

	private Session session;

	@Override
	public void findStudentBeanByTeacherName2PageBean(PageBean page, String teacherName) {
		// TODO Auto-generated method stub
		
		Criteria criteria = session.createCriteria(StudentBean.class);
		criteria.createAlias("teacher", "t",JoinType.LEFT_OUTER_JOIN);
		if(!StringUtils.isEmpty(teacherName)) {
			criteria.add(Restrictions.like("t.teacherName", teacherName, MatchMode.START));
		}
		
		//添加投影
		criteria.setProjection(Projections.rowCount());
		long totalRows = (long) criteria.uniqueResult();
		List<?> datas = null;
		if(totalRows > 0) {
			criteria.setProjection(null);
			criteria.setFirstResult(page.getIndex());
			criteria.setMaxResults(page.getRows());
			criteria.setResultTransformer(Criteria.ROOT_ENTITY);//这句话的作用  === HQL中编写的fetch
			datas = criteria.list();
		}
		page.setTotalRows(totalRows);
		page.setData(datas);
	}

}

 

三、多对多的关系

这里用玩家和游戏来举例，一个游戏可以多个玩家玩，一个玩家可以玩多个游戏

PlayerBean类：

private Integer id;
private String playerName;
    
private Set<GameBean> games;

GameBean类：

private Integer id;
private String gameName;

private Set<PlayerBean> players;

 

操作玩家数据（通过查询游戏名称，得到玩这个游戏的所有玩家）

1、利用hql

@Repository
public class PlayerDaoImpl implements IPlayerDao {
	
	private Session session;
	
	@Override
	public List<?> findPlayerBeanByGameName(String gameName) {
		// TODO Auto-generated method stub

		String hql = "From PlayerBean as p left join fetch p.games as g where g.gameName like concat(:gameName,'%')";
		Query query = session.createQuery(hql);
		query.setString("gameName", gameName);
		return query.list();
	}

}

2、利用Criteria

@Repository
public class PlayerDaoImpl implements IPlayerDao {

	
	private Session session;

	@Override
	public List<?> findPlayerBeanByGameName(String gameName) {
		// TODO Auto-generated method stub
	
		Criteria criteria = session.createCriteria(PlayerBean.class);
		criteria.createAlias("games", "g");
		
		if(!StringUtils.isEmpty(gameName)) {
			criteria.add(Restrictions.like("g.gameName", gameName, MatchMode.START));
		}
		
		return criteria.list();
	}

}

 

操作游戏数据（通过查询玩家名字得到该玩家所玩的所有游戏）

1、利用hql

@Repository
public class GameDaoImpl implements IGameDao {

	private Session session;

	@Override
	public List<?> findGameBeanByPlayerName(String playerName) {
		// TODO Auto-generated method stub
		String hql = "select DISTINCT(g) From GameBean as g left join fetch g.players as p where p.playerName like concat(:playerName,'%')";
		Query query = session.createQuery(hql);
		query.setString("playerName", playerName);
		return query.list();
	}

}

2、利用Criteria

@Repository
public class GameDaoImpl implements IGameDao {

	private Session session;
	
	@Override
	public List<?> findGameBeanByPlayerName(String playerName) {
		// TODO Auto-generated method stub
		
		Criteria criteria = session.createCriteria(GameBean.class);
		criteria.createAlias("players", "p");
		if(!StringUtils.isEmpty(playerName)) {
			criteria.add(Restrictions.like("p.playerName", playerName,MatchMode.START));
		}
		
		//去重，并且将关联对象，装配到主对象身上去
		criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
		return criteria.list();
		
	}

}

 

四、继承的关系

这里我用宠物来介绍，宠物中狗和猫

PetBean类：

private Integer id;
private String petName;

DogBean类：（继承宠物类）

public class DogBean extends PetBean{
 
     private Integer bone;
 
}

CatBean类：（继承宠物类）

public class CatBean extends PetBean{
 
    private int fish;
}

 

通过名字查询出数据，是猫还是狗（得到结果集）

1、利用hql

@Repository
public class PetDaoImpl implements IPetDao {

	private Session session;
	
	@Override
	public List<?> findPetBeanByName(String petName) {
		// TODO Auto-generated method stub
		String hql = "From PetBean as p where p.petName like concat(:petName,'%')";
		Query query = session.createQuery(hql);
		query.setString("petName", petName);
		return query.list();
		
	}

}

2、利用Criteria

@Repository
public class PetDaoImpl implements IPetDao {

	private Session session;

	@Override
	public List<?> findPetBeanByName(String petName) {
		// TODO Auto-generated method stub
		
		Criteria criteria = session.createCriteria(PetBean.class);
		if(!StringUtils.isEmpty(petName)) {
			criteria.add(Restrictions.like("petName", petName,MatchMode.START));
		}
		return criteria.list();
	}

}