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hibernate 添加操作、主键生成器、配置生成器、增删改查操作、分页查询、统计查询、Criteria、Native.md

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添加操作

操作代码

Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
session.save(dept);
tx.commit();//提交事务
session.close();

主键生成策略

Hibernate提供了一些内置主键生成器

  1. identity

    交给数据库自动生成主键值，适合MySQL和SQLServer。（注意：建表时需要追加自动增长设置）

     <id name="no" column="DEPTNO" type="integer">
 	<generator class="identity">
 	</generator>
 </id>

  2. sequence

    采用指定序列生成主键值，适合Oracle和DB2。

     <id name="no" column="DEPTNO" type="integer">
 	<generator class="sequence">
 		<param name="sequence_name">xxx</param>
 	</generator>
 </id>

  3. increment

    先查询主键最大值，然后加1再插入，适合各种数据库。

     <id name="no" column="DEPTNO" type="integer">
 	<generator class="increment">
 	</generator>
 </id>

  4. uuid

    采用uuid算法生成一个字符串类型主键值。

     <id name="no" column="DEPTNO" type="integer">
 	<generator class="uuid">
 	</generator>
 </id>

    (注意：表主键字段类型为varchar)

  5. native

    hibernate会根据方言设置自动选择identity或sequence等策略。

     <id name="no" column="DEPTNO" type="integer">
 	<generator class="native">
 	</generator>
 </id>

  6. assigned

    忽略，说明hibernate框架不管生成，需要按程序员指定的id值进行添加。

    （注意：默认值，需要在代码中调用setId(xxx)设置）

  7. 自定义主键生成器

    • 编写自定义生成器类,实现IdentifierGenerator接口

        public class DeptId implements IdentifierGenerator{

  	@Override
  	public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
  		//追加自定义主键规则逻辑
  		return 100;
  	}
  
  }

    • 配置生成器

        <id name="no" column="DEPTNO" type="integer">
  	<generator class="cn.xdl.util.DeptId">
  	</generator>
  </id>

更新操作

@Test
public void test2(){
	//部分更新，先查询，再修改
	Session session = HibernateUtil.getSession();
	Transaction tx = session.beginTransaction();
	Dept dept = session.get(Dept.class, 21);
	dept.setName("研发部");
	session.update(dept);//属于全部更新，根据id做条件更新其他字段值
	tx.commit();
	session.close();
}

删除操作

@Test
public void test3(){
	Dept dept = new Dept();
	dept.setNo(21);
	
	Session session = HibernateUtil.getSession();
	Transaction tx = session.beginTransaction();
	session.delete(dept);//根据id做条件删除
	tx.commit();
	session.close();
}

findById查询

@Test
public void test4(){
	Session session = HibernateUtil.getSession();
	Dept dept = session.get(Dept.class, 21);
	if(dept != null){
		System.out.println(dept.getName()+" "+dept.getLoc());
	}else{
		System.out.println("未找到记录");
	}
	session.close();
}

查询操作

HQL操作

Hibernate Query Language 面向对象查询语言

HQL语句是针对映射的对象和属性进行查询操作.

HQL语法结构和SQL相同，支持select..from..where..

HQL和SQL区别：

  • HQL属于面向对象查询;SQL属于面向结构查询
  • HQL用类名和属性名;SQL用表名和字段名
  • HQL中类名属性名大小写敏感；SQL中表名和字段名不敏感
  • HQL不支持select *写法,需要可以省略
  • HQL不支持join..on..中的on语句

SQL: select * from dept HQL: from Dept

SQL: select * from dept where dname like ? HQL: from Dept where name like ?

查询所有记录

@Test
public void test5(){
	Session session = HibernateUtil.getSession();
	String hql = "from Dept";
	Query<Dept> query = session.createQuery(hql);
	List<Dept> list = query.list();//执行HQL
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

带条件查询记录

@Test
public void test6(){
	Session session = HibernateUtil.getSession();
	String hql = "from Dept where name like ?";
	Query<Dept> query = session.createQuery(hql);
	query.setParameter(0, "java%");//给第一个?设置参数值
	List<Dept> list = query.list();//执行HQL
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

分页查询

@Test
public void test7(){
	Session session = HibernateUtil.getSession();
	String hql = "from Dept";
	Query<Dept> query = session.createQuery(hql);
	//设置分页参数
	query.setFirstResult(5);//抓取记录起点
	query.setMaxResults(5);//最大抓取数量
	List<Dept> list = query.list();//执行HQL
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

统计查询

@Test
public void test8(){
	Session session = HibernateUtil.getSession();
	String hql = "select count(*) from Dept";
	Query<Long> query = session.createQuery(hql);
	Long size = query.uniqueResult();
	System.out.println("记录总数:"+size);
	session.close();
}

Criteria操作

不足：对分组统计、多表查询、条件查询，会非常复杂。

查询所有记录

@Test
public void test10(){
	Session session = HibernateUtil.getSession();
	Criteria ct = session.createCriteria(Dept.class);//from Dept
	List<Dept> list = ct.list();
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

带条件参数查询(Restrictions)

@Test
public void test11(){
	Session session = HibernateUtil.getSession();
	Criteria ct = session.createCriteria(Dept.class);//from Dept
	ct.add(Restrictions.like("name", "%java%"));//where name like ?
	ct.addOrder(Order.desc("no"));//order by no desc
	List<Dept> list = ct.list();
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

NativeSQL操作

执行原始的sql语句。

查询所有记录

@Test
public void test14(){
	String sql = "select deptno,dname,loc from dept";
	Session session = HibernateUtil.getSession();
	NativeQuery<Dept> query = session.createNativeQuery(sql,Dept.class);
	List<Dept> list = query.getResultList();
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}

带条件参数的查询

@Test
public void test15(){
	String sql = "select deptno,dname,loc from dept where dname like :name";
	Session session = HibernateUtil.getSession();
	NativeQuery<Dept> query = session.createNativeQuery(sql,Dept.class);
	query.setParameter("name", "%java%");
	List<Dept> list = query.getResultList();
	for(Dept dept:list){
		System.out.println(dept.getNo()+" "+dept.getName()+" "+dept.getLoc());
	}
	session.close();
}