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  • hibernate的几种主键

     
    public class generator extends hibernateUtil {
    
    	/*
    	 * increment机制是int 查找当前id的最大值加1,两次查询效率底点
    	 * Hibernate: select max(id) from Person
          Hibernate: insert into Person (name, id) values (?, ?)
    	 */
    	@Test
    	public void testIncrement()
    	{
    		Session session = factory.openSession();
    		Transaction tran = session.beginTransaction();
    		Person p = new Person();
    		p.setName("yyyyy");
    		session.save(p);
    		tran.commit();
    		session.close();
    	}
    	
    	/*
    	 * Hibernate: insert into Person (name, id) values (?, ?)
    	 *   1;表必须支持自动增长机制 在Mysql中加入autoincrement
    	 *   2;主键的产生是数据库产生的,并不是由hibernate产生的
    	 *   3:比increment效率高 
    	 */
    	@Test
    	public void testIdentity()
    	{
    		Session session = factory.openSession();
    		Transaction tran = session.beginTransaction();
    		Person p = new Person();
    		p.setName("zzzzz");
    		session.save(p);
    		tran.commit();
    		session.close();
    	}
    	
    	/*
    	 * assigned产生机制
    	 * 由程序员手动添加id,一般测试的时候用,企业里面用的少
    	 */
    	@Test
    	public void testAssigned()
    	{
    		Session session = factory.openSession();
    		Transaction tran = session.beginTransaction();
    		Person p = new Person();
    		p.setName("zzzzz");
    		p.setId("222");
    		session.save(p);
    		tran.commit();
    		session.close();
    	}
    	
    	/*
    	 * UUID是hibernate内部生产的
    	 * id 必须是字符串类型的 
    	 * Hibernate: insert into Person (name, id) values (?, ?)
    	 */
    	@Test
    	public void testUUID()
    	{
    		Session session = factory.openSession();
    		Transaction tran = session.beginTransaction();
    		Person p = new Person();
    		p.setName("QQQQQ");
    		session.save(p);
    		tran.commit();
    		session.close();
    	}
    }
    
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  • 原文地址:https://www.cnblogs.com/linhong/p/4495325.html
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