Setting the bind variable value for the destination View Object in the View Link

I'm sharing an interesting use case that has come up recently from an internal team. The developer was looking for some hooks to set bind variable value used in the destination View Object participating in a View Link. Steve Muench has shared a useful tip to solve this case, let me share the same here for your reference, thanks Steve :)

The use case requirement is to set bind variable value conditionally for the child view object. Interestingly, the bind variable value is supposed to set programmatically only when the child view object is executed as part of master child coordination(through view link), in all other cases it's left to the caller.

The solution is very straight forward. The 11.1.1.5.0 release has new method added ViewObjectImpl::prepareRowSetForQuery(ViewRowSetImpl vrs) to intercept the VO query preparation phase. You may need to override this method, and add check for parent rows(to see whether VO instance is participating in master child coordination) and set the bind variable accordingly.

 @Override  
 public void prepareRowSetForQuery(ViewRowSetImpl vrs) {  
  RowSetIterator[] parentRows = vrs.getMasterRowSetIterators();  
  /**  
  * Check for parent Rows. If its not null, then query execution is   
  * triggered through ViewLink, get the required attributes from   
  * parent row( as per the use case ), and set the bind variable value  
  */  
  if (parentRows != null && parentRows.length > 0 &&  
      parentRows[0].getCurrentRow() != null) {  
      Number locId =  
           (Number)parentRows[0].getCurrentRow().getAttribute("LocationId");  
      //This is just a demo, to hide the employees whose salry is less   
      //than 3000$ from Location = 1500  
      if (locId != null && locId.intValue() == 1500) {  
           vrs.ensureVariableManager().setVariableValue("bindVarSalary",  
                                                                   3000);  
      }  
  }  
  super.prepareRowSetForQuery(vrs);  
 }  

Download

You can download the sample workspace from here.
[Runs with Oracle JDeveloper 11.1.1.5.0 (11g R1 PS4) + HR Schema]

A glance at the implementation

This example displays two employee tables, the one which follows master child relation with department table displays only those employee records having salary > 3000. This filtering is done by following the approach detailed above.

Learn More ...

There are a lot more points like this. If  you are curious to learn the internals of the ADF Business Components and ADF Binding Layer,  the following book is for you - Oracle ADF Real World Developer’s Guide.
More details about this book can be found in this post- http://jobinesh.blogspot.in/2012/07/pre-order-your-copy-of-oracle-adf-real.html