Creating and Updating records in single operation: sensible
markwhiting Jul 27, 2007 8:00 AMHi
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