Session.load: HibernateException or to return null?

freitasoo · **Joined:** Thu Aug 28, 2003 3:58 pm **Posts:** 19

Session.load() raises an exception if the bean can't be find by its id. Is there any way to return null instead of throwing an exception. I want to use this for my testCases (and in future implementations when I want to take some action if an entity cant be found).

See my test case:

----------------------------------------------
//Checks that the user was correctly inserted
Long result = addUser(user);
User expectedResult = loadUser(result);
assertEquals(user.fields(), expectedResult.fields());

//Now tests the exclusion
removeUser(result);

//If I try to load the user, it does not exists anymore so null should be returned
assertNul(loaduser(result));
----------------------------------------------

By throwing an exception, Hibernate makes it dificult to know if the user doesn't exists or if another internal error (a lost of conection with the DB for example) happened.

Null in my case should be a valid result?
Or is there another aproach to what I'm trying to do?

freitasoo · **Joined:** Thu Aug 28, 2003 3:58 pm **Posts:** 19

And where is the link to edit my messages. Lots of spelling and grammar errors on the one above.

breidenr · **Posted:** Thu Aug 28, 2003 4:13 pm

I have a class that acts as a facade to all Hibernate APIs. My load method look similar to what you suggested:

Code:

  public Object load(Class clazz, Serializable id) {
        
    Session session = getSession();
        
    try {

      try {
        return session.load(clazz, id);
      }
      catch (ObjectNotFoundException e) {
        // trap ObjectNotFoundException and return null instead. this is 
        // the expected behavior for most methods that use this method
        LOGGER.info(e.getMessage());
        return null;
      }
    ...
  }

gavin · **Posted:** Thu Aug 28, 2003 4:32 pm

No! You should not do this. Because load() might return a proxy, and not hit the db at all.

You should do:

Code:

(Foo) session.createQuery("from Foo foo where foo.id=?) .setParemeter(id).result();

breidenr · **Posted:** Thu Aug 28, 2003 4:51 pm

Thanks for the recommendation. Sorry for pointing people in the wrong direction. I have never used proxies, so this has never been a problem (yet).

Ryan

breidenr · **Posted:** Thu Aug 28, 2003 5:35 pm

Just to clarify...

The code posted does not seem to jive with the APIs. Would this be a recommended approach:

Code:

Iterator iter = session.createQuery("from Foo foo where foo.id=?").setParameter(1, id).iterate();
return (Foo) iter.hasNext() ? iter.next() : null;

gavin · **Posted:** Thu Aug 28, 2003 5:40 pm

yes, of course, i did some misprints

gavin · **Posted:** Thu Aug 28, 2003 5:41 pm

Oh, and also result() does not exist in 2.0. (Its in 2.1)

Bart Sawyer · **Posted:** Fri Aug 29, 2003 4:43 am

breidenr wrote:

I have a class that acts as a facade to all Hibernate APIs. My load method look similar to what you suggested:

Code:

  public Object load(Class clazz, Serializable id) {
        
    Session session = getSession();
        
    try {

      try {
        return session.load(clazz, id);
      }
      catch (ObjectNotFoundException e) {
        // trap ObjectNotFoundException and return null instead. this is 
        // the expected behavior for most methods that use this method
        LOGGER.info(e.getMessage());
        return null;
      }
    ...
  }

Quote:

No! You should not do this. Because load() might return a proxy, and not hit the db at all.

I'm a newbie so sorry for the question, but can someone explain this a little further, I still don't get why the code above is not such a good idea.

freitasoo · **Joined:** Thu Aug 28, 2003 3:58 pm **Posts:** 19

I ask the same thing. What about the proxie stuff?

freitasoo · **Joined:** Thu Aug 28, 2003 3:58 pm **Posts:** 19

Also, I have a method to load any kind of objects so I need to use load().

That's because if I use queries I need to know what object I want to load and then its name/properties can vary quite a bit. Also I do not want to pass Strings to complete the query string.

Code:

publiv Object loadObject(String name, String idProperty, Long value) {
  ...
  session.find("from " + name + " where " + idProperty + " = ?"...
}

Ugly don't u think? Is there any other aproach instead?

max · **Posted:** Fri Aug 29, 2003 8:17 am

freitasoo wrote:

Also, I have a method to load any kind of objects so I need to use load().

That's because if I use queries I need to know what object I want to load and then its name/properties can vary quite a bit. Also I do not want to pass Strings to complete the query string.

Code:

publiv Object loadObject(String name, String idProperty, Long value) {
  ...
  session.find("from " + name + " where " + idProperty + " = ?"...
}

Ugly don't u think? Is there any other aproach instead?

Dude! .id is a keyword in hql! So the code should just be:

Code:

public Object loadObject(Class class, Object idvalue) {
  ...
  session.find("from " + class.getName() + " where id = ?", idvalue);
}

gavin · **Posted:** Fri Aug 29, 2003 2:43 pm

Actually:

Code:

public Object loadObject(Class class, Object idvalue)  {
  return session.find("from " + class.getName() + " x where x.id = ?", idvalue);
} 

efender · **Posted:** Fri Aug 29, 2003 3:26 pm

How to do that with a compound id? I tried this:

Code:

List list = session.find("from " + stateName + " x where x.id = ?", identity, Hibernate.SERIALIZABLE);

and

Code:

List list = session.find("from " + stateName + " x where x.id = ?", identity, Hibernate.serializable(identity.getClass()));

but I'm getting

Code:

net.sf.hibernate.QueryException: path expression ends in a composite value: category0_.id [from com.*****.cc.objectlib.category.CategoryState x where x.id = ?]

freitasoo · **Joined:** Thu Aug 28, 2003 3:58 pm **Posts:** 19

Oh (blush)!! I didn't know id was a keyword. What a dumbass!!!