Representing many-to-many relationships

Question

The data structure I am working with is a many-to-many relationship between clients and contacts, managed by a client_contact intersection table
I have been rather unsuccessfully trying to use the JHeadstart generator to generate a master-detail style relationship between clients and contacts. The new intersection shuttle is great for being able to be maintain the intersection table and have that working fine but I would also like to set up a master-detail group
I have created a ContactsForClient view that combines the Contacts and Client_contacts entities with a bind parameter of client id and created a view link between clients VO and the ContactsForClient VO. Setting this up in the JHeadstart generator works fine for displaying and modifying the associated contacts - but adding new contacts is where the problem lies. The ContactsForClient group uses a table structure with empty rows at the bottom for inserting new contacts. I am unsure of how to be able to manage the client_contact instersection table in behind the scenes. The ClientContactsImpl fires first - at which stage I only have client id and not the contact id. I want to be able to force the ContactsImpl to run first and retrieve the DB Sequence that was used to populate the contact id on the contacts table, using that to populate the client-contacts table.
I saw some code to force a new dept to be posted before the emp record and thought I could utilise that but it does not work
  public void postChanges(TransactionEvent e) {
    System.out.println("In postChanges");
    if (getPostState() == STATUS_NEW)
      System.out.println("Status is new");
      ContactsImpl newContact = getContacts();
      if (newContact != null) {
        System.out.println("newContact not null");
        if (newContact.getPostState() == STATUS_NEW) {
          newContact.postChanges(e);
          // retrieve DB sequence used to populate contacts ct_id
          // and use to set clientcontacts ct_id
          System.out.println("newContact changes posted");
    super.postChanges(e);
  }newContact is always null ! I realise I could create separate screens to create the contacts and then the intersection-shuttle to assign them to a client but is there anyway I can do this in a way that mimics normal master-detail JHeadstart functionality ?
Any help would be greatly appreciated !

Answer 1

Managed to get my problem solved - I was over-complicating things ! I did however run into the reason (after a substantial process of elimination) why the postchanges method was not working as expected.
  public void postChanges(TransactionEvent e) {
    if ((getPostState() == STATUS_NEW) || (getPostState() == STATUS_MODIFIED)) {
      EntityImpl gio = getGoodsInOut();
      if (gio != null) {
        if (gio.getPostState() == STATUS_NEW) {
          gio.postChanges(e);
    super.postChanges(e);
  }My master EO is GoodsInOut and my detail EO is product. When I was running this code from the ProductsImpl, the getGoodsInOut() was always returning a null value and therefore I was unable to force the posting of the master before the detail. The problem turned out to be a "before insert for each row" trigger on the GoodsInOut table. This trigger was just setting the sequence but for some reason, after firing, causes the relationship between the GoodsInOut master and the Products detail to be lost, with getGoodsInOut() returning null. As soon as I dropped the database trigger and set the sequence in the EO's create method - it worked fine. I realise this is a "JDeveloper" question rather than a "JHeadstart" question so I will post this on the JDeveloper forum as well but thought you may have some ideas on why the database trigger is causing that behaviour and also how I can still retrieve the GoodsInOut EntityImpl with a database trigger (want this for auditing purposes) - perhaps make the call to getGoodsInOut at an earlier stage in the processing (ie before the database trigger runs) ?
Cheers,
Brent Harlow