ADF BC Groovy – showing old values along with new part II – via ViewRowImpl

A while back I posted about using Groovy within our ADF BC EOs to expose the new and old values of a particular attribute. This method described in that post works fine if you've access to the EOs in the same project. However in our current project EOs are segmented in another application workspace project for reuse and ADF Library JARed into our existing "master" ADF BC workspace project. The external EOs are intended to be shared by multiple other sub-systems, and it really didn't seem ideal to include additional transient attributes on all the attributes in the shared EOs just in case some other application needs them, mostly they wont want this specific requirement.

This lead to the requirement to include the same functionality, namely transient attributes based on a Groovy expression to return the old value of the attributes, from our project's VOs instead. In other words, if a VO needs them, it includes 'em.

We immediately hit a problem on implementing this requirement. The EntityImpl.getPostedAttribute(index) method is a protected method, and there is no equivalent ViewRowImpl method. Arguably it should be provided at the ViewRowImpl level, and a search of the JDev OTN forums shows it's an old issue and I guess not likely to change anytime soon.

Without an immediate change to the ADF BC framework, we needed to find another solution. What we came up with:

(As per the original post we'll assume we're looking at the Employees EO and Position attribute)

1) By default extend the ADF Business Components Framework as per section 37.1 Globally Extending ADF Business Components Functionality of the Fusion Guide.

2) In the extended EntityImpl class, say common.model.CommonEntityImpl, create a public exposed version of the getPostedAttribute method

public Object getPostedAttribute(int index) {
  return super.getPostedAttribute(index);
}

3) For the specific VO interested in showing the old values of an attribute, create the associated ViewRowImpl (say EmployeesViewRowImpl). Ensure in the generated class an accessor method to access the underlying EntityImpl has been created, ie:

public EntityImpl getEmployees() {
  return (EntityImpl)getEntity(0);
}

4) In the local project's VO transient attributes to show the old values base it on the following Groovy expression:

adf.object.getEmployees().getPostedAttribute(model.entities.EmployeesImpl.POSITION)

What it does:

a) adf.object.getEmployees() calls the EmployeesViewRowImpl.getEmployees() method we checked existed in step 3, to retrieve the associated EntityImpl for the current ViewRowImpl

Note if you haven't undertaken step 3 to generate the associated ViewRowImpl, alternatively you could just call getEntity(0) instead in your Groovy expression. However I'd be cautious on doing this as you're relying on future upgrades of the framework not changing what's at position zero.

b) .getPostedAttribute() calls the now publically exposed getPostedAttribute method we created in the common.model.CommonEntityImpl that gives us the ability to get at old attribute values in the EO

c) The parameter model.entities.EmployeesImpl.POSITION grabs the index position of the Surname field in the EO. Note we need to use the EntityImpl field position rather than the ViewRowImpl field positions, as the order of the fields can be different.


Of interest to this post, an old discussion on the ADF Enterprise Methodology Group, was do most projects extend the ADF framework as per section 37.1 Globally Extending ADF Business Components Functionality? As can be seen from this specific blog post this shows another reason to include the extended classes from day 1 of any ADF development.


Final caveat: Please note this post is mostly for self documentation purposes, posted here so others can make use of it, but is not guaranteed to work; honestly I haven't tested this thoroughly nor has it been placed in a production environment yet. As such be careful to check it works for you, your mileage may vary. If you find any problems it would be appreciated if you could post your findings here to assist other readers.