Parent-Child using messageChoice to table

Question

I have a UIX form that has two components on it. A <messageChoice> that is displaying parent data (e.g. departments) and a <table> that is displaying the employees in the department.
I would like to be able to select a department from the <messageChoice> and have the employees displayed in the <table>.
The model includes a viewlink between the parent table and the child table to force the relationship.
When I create the <messageChoice> as a LOV I get a message in the "List Binding Editor" that says:
"You have selected a detail data collection as the target (data collection) and master data collection as the source (data collection).
Target data collection will not be modified but navigated based on the selection in the LOV.
Want to proceed?"
(This looks ok to me.)
I build the rest of the page and have tried to add an event action to the <messageChoice> but I have not been able to get the parent VO to be set to the selected record so that the child will display the associated data. The first record that is showing has the correct child records.
The UIX looks like this:
<messageChoice id="mcSID" model="${bindings.Dept}">
<contents childData="${bindings.Dept.displayData}">
<option model="${uix.current}"/>
</contents>
<primaryClientAction>
<fireAction event="selectDID" formSubmitted="false">
<parameters>
<parameter key="currentDID" value="${bindings.Did}"/>
</parameters>
</fireAction>
</primaryClientAction>
</messageChoice>
<spacer width="10" height="10"/>
<styledText text="CURRENT DID: "/>
<styledText text="${param.currentDID}"/>
I believe that I need to be able to trap the id of the record that has been selected so that the parent VO can be set to this value. The child VO should follow suit. However, I am not able to get the value from the messageChoice. How can I get this to work?

Answer 1

Hi Vince -
I spent some time yesterday trying to put together a solution based on the Employees/Departments tables of the HR sample schema. Like you, I started by trying to bind the mesageChoice such that the Departments view object is used for the source data collection and the Employees view object on the other side of the view link is the target data collection. When creating the binding, I too saw the "Target data collection will not be modified but navigated based on the selection in the LOV" message, which seemed like a good sign. Although the messageChoice does get populated correctly, no records are found when I try to select a new department.
I recruited a co-worker who has more experience working with ADF BC to help out, and he proposed a slightly different solution, which we were able to get up and running. I'm not sure whether this is necessarily the best solution, and there most certainly are other ways to accomplish the same functionality, but the solution seems to work fairly well, so I thought it would be worth sharing.
The main change in new solution has to do with the target data collection that is used when setting up the list binding. In the earlier solutions that both you and I attempted, the target data collection is the "detail" view object itself (ie. the Employees view object hanging off of the Departments view object via a view link). Instead of going this route, my colleague suggested using an intermediate "transient" view object to hold the result of the list selection. This view object is linked to a new instance of the Employees view object. The idea is that when the list selection changes, it is applied to the new transient view object, which in turn restricts the employees that are included in the linked Employees view object.
Here are steps we followed to get this up and running:
1. Create the basic data model
We used the HR schema, and created view objects from the EMPLOYEES and DEPARTMENTS tables. This produced an application module with the following view objects:
- EmployeesView1: All employees
- DepartmentsView1: All departments
- EmployeesView3: View of employees linked to DepartmentsView1
2. Define a transient view object for holding selection data
Using the "Create View Object" wizard, we set up the view object as follows:
Step 1: Set name to "TransientDepartmentsView"
Step 2: Do not select any entities (since the view object is transient)
Step 3: Create a new attribute named "DepartmentId". Set the type to "Number". Set updateable to "Always". Check "Selected In Query". Set Alias to "DEPARTMENT_ID".
Step 4: Leave attribute settings as is
Step 5: Set query to "SELECT 10 AS DEPARTMENT_ID FROM DUAL".
Accept all other defaults in remaining steps and finish.
The new view object has a single attribute "DepartmentId", which will be used to store the results of the list binding. The "SELECT 10 AS DEPARTMENT_ID FROM DUAL" serves two purposes. The "FROM DUAL" clause ensures that the view object only ever contains a single row. The "SELECT 10 AS DEPARTMENT_ID" ensures that a default department id (10) is provided, so that the initial page render will display the employees from the default department.
3. Define a view link between the TransientDepartmentsView and EmployeesView
In the "Create View Link" wizard, enter the following values:
Step 1: Set name to "TransientEmpDeptFKLink".
Step 2: Select the TransientDepartmentsView's DepartmentId attribute for the source. Select the EmployeesView's DepartmentId for the destination. Click Add.
Accept all other defaults in remaining steps and finish.
5. Add new view object instances to the application module.
In steps 3 and 4, we enhanced our model definition to include a new view object and view link. Now, we need to create instances of these objects in the application module, as follows:
- Double click on the AppModule node in the Applications Navigator to bring up the Application Module editor.
- Select the "Data Model" node to display the available model objects.
- Select the TransientDepartmentsView node in the "Available View Objects" pane.
- Click the right arrow button to add a new instance to the application module. You should see a new view object instance named "TransientDepartmentsView1" appear in the Data Model pane, which should be selected.
- Back in the Available View Objects pane, select the "EmployeesView via TransientEmpDeptFKLink" node. Leaving the "TransientDepartmentsView1" node selected on the Data Model pane, click the right arrow. You should now see an "EmployeesView4 via TransientEmpDeptFKLink1" node appear under the "TransientDepartmentsView1" node in the Data Model pane.
- Click OK
At this point we're done preparing the data model. Before we move on, we can test the model in the Oracle Business Component Browser. Bring up the BC Browser by right-clicking on the "model" node in the Application Navigator and selecting "Run". You should see our new transient view object and link under the application module. If you double-click the TransientEmpDeptFKLink1, you should see a "DepartmentId" field linked to the employees view. Try entering a new department id (eg. "90") into the field and hit enter. The emloyees list should be filtered accordingly.
6. Set up the page flow.
In my sample, I just add a single Data Page ("/dataPage1") to the struts-config.xml. To create the corresponding UIX page, double click the Data Page node and select "/dataPage1.uix".
7. Create the messageChoice and set up list binding.
In the Data Control pallete, select the DepartmentId attribute of the TransientDepartmentsView1 view object. Set "Drag and Drop As:" to "MessageChoice", and drag the DepartmentId node to the UIX page. This brings up the List Binding Editor.
In the List Binding Editor, change the List Binding Mode to "LOV Mode". The target data collection should already be populated. Select DepartmentsView1 for the source data collection, since we want to display all available departments in our messageChoice. Click New/OK to create a new source iterator. Click Add and verify that both the source and target attribute is "DepartmentId".
In the LOV Display Attributes pane, select DepartmentId and/or DepartmentName as desired.
8. Set up the client action.
From the property inspector, launch the primaryClientAction editor. Select "Fire action by submitting Form" and click OK. This will set up a <primaryClientAction> element in your uiXML code. By default, the fireAction client action assumes a default event named "update". We don't want to fire a UIX event - we just want to submit the form and allow ADF to handle the postback. So, to suppress the default "update" event, go into your uiXML and add 'event=""' to the <fireAction> element. Your <fireAction> element should look like this:
<fireAction event="" formSubmitted="true"/>
9. Set up the employees table.
Back in the data control palette, select the "EmployeesView4" node, which should be under the "TransientDepartmentsView1" node. Make sure "Drag And Drop As: " is set to "Read-Only Table", and Drag the EmployeesView4 node onto the UIX page. You should see the table appear with appropriate bindings.
At this point, you should be good to go. Try running the /dataPage1 Data Page from the struts-config.xml editor. When the page first comes up, you should see the default department selected (in our sample, that would be 10/Administration) and the table should display the corresponding employees. When a new department is selected, the <fireAction> triggers a form submission. This in turn causes the selected value to be applied to the transient departments view object, and the linked employees view object to be filtered accordingly. When the page is re-rendered, the employees table should be updated to reflect the currently selected department.
Hope this helps solve your problem. As I mentioned above, I'm sure there are other ways to do this. If anyone has recommendations for a simpler solution, please let us know!
Andy