Domain Object Model and Hibernate detached object

[yfmoan]

found a second work around method , this is more OO - avoid using detached object .

Since the problem is caused by the hibernate detached object which cannot recognise the dirty properties changed if select-before-update attribute is not set to "true" , we just do our best to avoid it.

my problem is caused by the "reuse" of libraryUser which are return from formBackingObject() to onSubmit() in BorrowForm.java ,

public class BorrowForm extends AbstractLibraryFormController {

	public BorrowForm() {
		setCommandClass(LibraryUser.class);
		setCommandName("libraryUser");
		setSessionForm(true);
	}
	

	protected Object formBackingObject(HttpServletRequest request)
			throws ServletException {

		String cardKey = request.getParameter("cardKey");
   ...
		LibraryUser libraryUser = getLibrary().findLibraryUser(cardKey);
   ...
		return libraryUser;
	}
   ...
	public ModelAndView onSubmit(HttpServletRequest request,
			HttpServletResponse response, Object command, BindException errors)
			throws Exception {

		String barcode = request.getParameter("barcode");
		long lutId = RequestUtils.getLongParameter(request,"libraryUserTypeId", 0);

		// the below libraryUser is a detached object ! 
		// l cannot reuse it ! it cause difficulty l have mention in my first post.
		// **********************************************************************
		LibraryUser libraryUser = (LibraryUser) command;

		Long libraryUserId = libraryUser.getId();
		Long libraryUserTypeId = new Long(lutId);

		// l get another libraryuser inside the method lend(..) , see the code below
		// *********************************************************************
		getLibrary().lend(barcode,libraryUserId,libraryUserTypeId);

		return new ModelAndView(getSuccessView()+ "?" + "cardKey="
				+ libraryUser.getCardKey());

	}

my service class LibraryImpl.java ,

public class LibraryImpl implements LibraryFacade {
...
	public void lend(String barcode,Long libraryUserId,Long libraryUserTypeId){
		
		LibraryUser libraryUser = loadLibraryUser(libraryUserId.longValue());
		LibraryUserType libraryUserType = null;
		
		Set libraryUserTypes = libraryUser.getLibraryUserTypes();
		Iterator it = libraryUserTypes.iterator();
		
		while (it.hasNext()) {

			LibraryUserType lut = (LibraryUserType) it.next();

			if (lut.getId().equals(libraryUserTypeId)) {
				libraryUserType = lut;
				break;
			}
		}

		Item item = loadItemByBarcode(barcode);
		
		libraryUser.lend(item,libraryUserType);

		// l can use storeLibraryUser(..) now , it won't cause multi-unwanted update 
		// ***********************************************************************
		storeLibraryUser(libraryUser);
		
	}
}

LibraryUser.java's lend method , notice that it is return a void instead of a borrow ,

	public void lend(Item item,LibraryUserType libraryUserType) {
		
		Borrow newBorrow = new Borrow();
		newBorrow.setItem(item);
		newBorrow.setLibraryUser(this);
		newBorrow.setLibraryUserType(libraryUserType);

		Date today = new Date();
		newBorrow.setBorrowDate(today);
		
		long oneDay = 86400000;
		// check the convertion OK or not -> int to long
		long duration = libraryUserType.getDuration().longValue();
		long itemDuration = item.getItemDuration().getItemDurationValue().longValue();
		Date dueDate =  new Date(today.getTime()+(duration*oneDay)+(itemDuration*oneDay));
		newBorrow.setDueDate(dueDate);
		
		this.getBorrows().add(newBorrow);
		
	}

it insert only one borrow , hibernate knew who have been modified.

...
Hibernate: insert into BORROWS (VERSION, BORROW_DATE, DUE_DATE, RETURN_DATE, REPORTLOST_DATE, RENEWED_NO, LIBRARY_USER_TYPE_ID, ITEM_ID, USER_ID) values (?, ?, ?, ?, ?, ?, ?, ?, ?)
...

Remark :

1. This is fast code , just to illustrate idea.
2. l don't know what will happen if l keep avoiding detached object , l think this is not better than the psuedo code.

Alarmnummer , thanks for the explaination , but l still don't understand second answer

And the save method is needed if you bind information to the domain objects and need to save it. So a save method can bypass all logic.

it seems that you are exposing your service object for someone to take control , ?? .

-If you are a 'professional' you have learned to give up hope and use what you have got. You have learned that the struggeling is normal and finally you accept it as the way you do your work and start to defend it if others complain because it sucks. In some cases you even make up 'design patterns' with complicated names to deal with the problems of the bad solution.
-Or you are to stupid to realise it sucks in the first place and do it because this is the way everybody does it.
-Or you find it great because: if it is so difficult to use, it must be good!

I`m a littlebit sarcastic, but I hope you get the point.

Yes , l understood .

moon

[yfmoan]

Hi cepage ,

How is LibraryUser being instantiated?

my libraryUser is instantiated by Hibernate, l have thought about to use DependencyInjectionInterceptorFactoryBean to inject the dependencies , but this will make my libraryUser depend on DAO or service object , although oliverhutchison wrote in another post "DAO Reference Inside an Entity Domain Object?" that :

As long as you services layer is defined with an interface there's nothing to fear.

l am not going through this way now , basic instinct told me not to , hihi , may be l will try it later when l hit the stone , . The way l am chosing fall in the second category model in the chinese forum l described above (It's supposed to be a rich DOM), l will report back if l hit stone.

Remark:

The chinese author , robbin , summarize three model (l describe roughly):
1. ADOM
2. Rich DOM (domain not depend on DAO)
3. Rich DOM (domain depend on DAO)

If you don't know chinese , you still can see from the codes to guess what he means , , l cannot translate the article without the permission of the author (it is not easy to translate 2 , because l don't understand a lot , :oops: ).


It seem that you are writing application with DAO inject into domain object (This fall into the third category model), did you hit any stone ?

moon