如果我从我的代码中排除 session.evict() 会发生什么？

Question

I am new to hibernate. I would like to know if we have any alternatives for session.evict(). I have commented that line and my logic works fine.

Answer 1

session.evict() method is used to remove a particular object from cache associated with the session. So removing it will force the hibernate to fetch the object from database instead of looking into cache. Example

Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
try
{
SomeEntity myEntity= (SomeEntity) session.load(SomeEntity.class, new Integer(1)); //look in cache (will not be found) if not found then fetch from database
System.out.println(myEntity.getName());

myEntity = (SomeEntity) session.load(SomeEntity.class, new Integer(1)); //look in cache(will be found) if not then fetch from database
System.out.println(myEntity.getName());

session.evict(myEntity); // will remove from cache

myEntity = (SomeEntity) session.load(SomeEntity.class, new Integer(1)); // object will again be fetched from database if not found in second level cache
System.out.println(myEntity.getName());
}
finally
{
session.getTransaction().commit();
HibernateUtil.shutdown();
}

Edit: Session.evict() will remove the entity from first level cache and after removing the object from the session, any change to object will not be persisted. The associated objects will also be detached if the association is mapped with cascade="evict".

Hope it helps!!