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

[matt.drees]

Seems like you'd need a entityManager.persist() for your new myEntity.

[markwhiting]

Good spot.

I managed to lose that line of code when copy/pasting . The penultimate line in createNewEntity() should read:

entityManager.persist(myEntity);

With this in place, does this approach look sensible - or is there a 'tidier' way?

Thanks

[tim_ph]

The way I do it is different because the way I define object relationship in hibernate (collection of items SAVE / DELETE_ORPHAN).
- Create a table of existing items in collection and hidden panel for object edit.
- Click add item: Create new object and add to collection
- Show edit panel of new object
- Hit update button of panel: just hide the panel. You should see object updated in table.