休眠:检查对象是否存在 [英] Hibernate: check if object exists
问题描述
假设, A 类型的对象存储在数据库中。这里是我使用hibernate从数据库加载特定的一个的方式:
org.hibernate.Session session = ...;
long id = 1;
A obj = session.load(A.class,id);
如果id = 1的对象不存在,我会得到 ObjectNotFoundException 。但有没有办法检查这样的对象是否存在,而不必捕捉异常?我想要的是这样的:
org.hibernate.Session session = ...;
long id = 1;
boolean exists = session.exists(A.class,id);
if(exists){
// do smth .....
}
无法找到它的hibernate文档...
您可以使用 session.get
:
public Object get(Class clazz,
Serializable id)
抛出HibernateException
如果数据库中不存在该对象,它将返回null。您可以在 Hibernate API文档中找到更多信息。
Suppose, objects of type A are stored in DB. Here's the way I load specific one from DB using hibernate:
org.hibernate.Session session = ...;
long id = 1;
A obj = session.load(A.class, id);
If object with id=1 doesn't exist I will get ObjectNotFoundException. But is there a way to check if such object exists without having to catch the exception? What I would like to have is smth like:
org.hibernate.Session session = ...;
long id = 1;
boolean exists = session.exists(A.class, id);
if(exists){
// do smth.....
}
Couldn't find it hibernate docs...
You can use session.get
:
public Object get(Class clazz,
Serializable id)
throws HibernateException
It will return null if the object does not exist in the database. You can find more information in Hibernate API Documentation.
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