Hibernate DAO中的几个方法

* save()方法提供了向数据库中添加数据的功能,但只能添加,这个DAO没有生成Update()的方法 
* 但你可以简单的八save()方法改称具有Update功能:将getSession().save * (transientInstance);这句改成 
* getSession().merge(transientInstance);或者getSession().saveOrUpdate 
*  (transientInstance); 
public void save(User transientInstance) { 
  log.debug("saving User instance"); 
  try { 
   Session session=getSession(); 
   Transaction tx=session.beginTransaction(); 
   session.save(transientInstanc); 
   tx.commit(); 
   session.close(); 
   log.debug("save successful"); 
  } catch (RuntimeException re) { 
   log.error("save failed", re); 
   throw re; 
  } 
} 


delete()方法用来删除的 实际上我们会用下边的这个方法进行删除 

public void delete(Integer id){ 
  log.debug("deleting User instance..."); 
  User user=findById(id); 
  delete(user); 
} 

public void delete(User persistentInstance) { 
  log.debug("deleting User instance"); 
  try { 
   Session session=getSession(); 
   Transaction tx=session.beginTransaction(); 
   session.delete(persistentInstance); 
   tx.commit(); 
   session.close(); 
   log.debug("delete successful"); 
  } catch (RuntimeException re) { 
   log.error("delete failed", re); 
   throw re; 
  } 
} 

根据编号进行查找 

public User findById(java.lang.Integer id) { 
  log.debug("getting User instance with id: " + id); 
  try { 
   User instance = (User) getSession().get("hbm.User", id); 
   return instance; 
  } catch (RuntimeException re) { 
   log.error("get failed", re); 
   throw re; 
  } 
} 

findByExample()方法实现的功能相当于"select * from Usertable"实现的功能就是查询所有 数据. 

public List findByExample(User instance) { 
  log.debug("finding User instance by example"); 
  try { 
   List results = getSession().createCriteria("hbm.User").add( 
     Example.create(instance)).list(); 
   log.debug("find by example successful, result size: " 
     + results.size()); 
   return results; 
  } catch (RuntimeException re) { 
   log.error("find by example failed", re); 
   throw re; 
  } 
} 

findByProperty()方法用来灵活的提供一种按条件查询的方法,你可以自己定义要按什么样的方 式查询. 

public List findByProperty(String propertyName, Object value) { 
  log.debug("finding User instance with property: " + propertyName 
    + ", value: " + value); 
  try { 
   String queryString = "from User as model where model." 
     + propertyName + "= ?"; 
   Query queryObject = getSession().createQuery(queryString); 
   queryObject.setParameter(0, value); 
   return queryObject.list(); 
  } catch (RuntimeException re) { 
   log.error("find by property name failed", re); 
   throw re; 
  } 
} 


public List findByName(Object name) { 
  return findByProperty(NAME, name); 
} 

public List findBySex(Object sex) { 
  return findByProperty(SEX, sex); 
} 

public List findByAge(Object age) { 
  return findByProperty(AGE, age); 
} 

public List findAll() { 
  log.debug("finding all User instances"); 
  try { 
   String queryString = "from User"; 
   Query queryObject = getSession().createQuery(queryString); 
   return queryObject.list(); 
  } catch (RuntimeException re) { 
   log.error("find all failed", re); 
   throw re; 
  } 
} 

将传入的detached状态的对象的属性复制到持久化对象中，并返回该持久化对象  如果该session中没有关联的持久化对象，加载一个，如果传入对象未保存，保存一个副本并作为持久对象返回，传入对象依然保持detached状态。 

可以用作更新数据 

public User merge(User detachedInstance) { 
  log.debug("merging User instance"); 
  try { 

    Session session=getSession(); 
   Transaction tx=session.beginTransaction(); 
   
   User result = (User) session.merge(detachedInstance); 
   tx.commit(); 
   session.close(); 
   log.debug("merge successful"); 
   return result; 
  } catch (RuntimeException re) { 
   log.error("merge failed", re); 
   throw re; 
  } 
} 

将传入的对象持久化并保存。 如果对象未保存（Transient状态），调用save方法保存。如果对象已保存（Detached状态），调用update方法将对象与Session重新关联。 

public void attachDirty(User instance) { 
  log.debug("attaching dirty User instance"); 
  try { 
   getSession().saveOrUpdate(instance); 
   log.debug("attach successful"); 
  } catch (RuntimeException re) { 
   log.error("attach failed", re); 
   throw re; 
  } 
} 

将传入的对象状态设置为Transient状态 

public void attachClean(User instance) { 
  log.debug("attaching clean User instance"); 
  try { 
   getSession().lock(instance, LockMode.NONE); 
   log.debug("attach successful"); 
  } catch (RuntimeException re) { 
   log.error("attach failed", re); 
   throw re; 
  } 
}