[jboss-user] [JBoss Seam] - Creating and Updating records in single operation: sensible

[markwhiting]

Hi

I'm interested to hear people's opinions on the way I've implemented a solution. I'd like to know if there's a cleaner or simpler pattern...



Requirement:

When a user clicks an 'update' button, create a new record in a table and also update an existing record in the same table. The UI page uses <h:inputText/> fields. Application flow:

1. User selects an existing record from a CRUD page and is presented with an edit page for a that record
2. User edits some fields of that record and clicks 'update'
3. A new record must be created, which is a copy of the existing record but with any fields the user changed in step 2 upated with those changes
4. Some non-UI fields of the existing record must be changed and the record then updated in the table (this record must otherwise remain unchanged)



A solution:

Relevant code (abridged for brevity):


i.  Edit page extract:

note: This page is rendered after the user selects a record from a different CRUD page.

<h:form>
  | 
  | 	<s:decorate id="decoration" template="edit.xhtml">	
  | 		<h:inputText id="one"
  | 			value="#{myEntityHome.instance.UIProperty}" >
  | 			<a:support event="onblur" reRender="decoration"
  | 				bypassUpdates="true" ajaxSingle="true" />
  | 		</h:inputText>
  | 	</s:decorate>
  | 
  | 	<h:commandButton id="update" value="Update" action="#{myEntityHome.update}" />
  | 
  | </h:form>



ii.  Extended Home component:

note:

a. find() is invoked in step 1 (when the user selects a record on the CRUD page).

b. update() is invoked in step 2 (when the user clicks the update button).

c. Assume MyEntity is a simple EJB Entity with properties corresponding to those referenced below.


  | @Name("myEntityHome")
  | public class MyEntityHome extends EntityHome<MyEntity>
  | 
  | 	private MyEntity existingEntity;
  | 	private List<AssociatedEntityList> associatedEntityLists = new ArrayList<AssociatedEntityList>();
  | 	
  | 	@In(create = true)
  | 	EntityManager em;
  | 
  | 	public List<AssociatedEntityList> getAssociatedEntityLists() {
  | 		return associatedEntityLists;
  | 	}
  | 
  | 	@Override
  | 	public MyEntity find() {
  | 
  | 		// Store the contents of the existing entity
  | 		MyEntity myEntity = super.find();
  | 		existingEntity = new MyEntity(myEntity.getId(),	
  | 			myEntity.getUIProperty(),
  | 			myEntity.getNonUIProperty(),
  | 			myEntity.getAssociatedEntityLists());
  | 		return myEntity;
  | 	}
  | 	
  | 	
  | 	@Begin(join = true, flushMode = FlushModeType.MANUAL)
  | 	@Override
  | 	@Transactional
  | 	public String update() {
  | 
  | 		// For step 3
  | 		MyEntity myEntity = createNewEntity();
  | 					
  | 		// For step 4: Refresh the existing entity as the user may have changed
  | 		// some UI fields, which must not be updated in the db
  | 		em.refresh(getInstance());
  | 		
  | 		// For step 4
  | 		getInstance().setNonUIProperty("changed");
  | 		
  | 		entityManager.flush();
  | 		Contexts.removeFromAllContexts("myEntityHome");
  | 		return "createdAndUpdated";
  | 	}
  | 	
  | 	
  | 	private MyEntity createNewEntity() {
  | 
  | 		MyEntity myEntity = new MyEntity();
  | 
  | 		// Copy contents of current UI fields into the newly created entity
  | 		myEntity.setUIPropertyOne(getInstance().getUIPropertyOne());
  | 
  | 		// Copy contents of non-UI fields into the newly created entity
  | 		myEntity.setNonUIPropertyOne(getInstance().getNonUIPropertyOne());
  | 
  | 		// Copy associated entities into the newly created entity
  | 		for (AssociatedEntityList ael : associatedEntityLists)
  | 			ael.setMyEntity(myEntity);
  | 		myEntity.setAssociatedEntityLists(associatedEntityLists);
  | 
  | 		return myEntity;
  | 	}

As you can see, I'm using EntityManager refreshing and manual flushing and am having to make a 'clone' (which could be done by implementing Cloneable instead) of the existing entity in createNewEntity().


Any feedback appreciated...


Thanks


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