SCA Recursion

A service I’m designing for a client will retrieve mortgage details to be displayed by the web tier.

It is common for mortgages to consist of a main account which itself is composed of a number of sub-accounts, and it is not inconceivable for the sub-accounts themselves to have further sub-accounts.

To retrieve the entire tree my service has to call the mortgage account back-end multiple times while drilling down into accounts for sub-accounts to retrieve.

All those main and sub accounts are the same data type, so recursion seemed a good fit: I receive a request with a mortgage account Id, call the back end service who responds with account details, including a list of sub-account Ids, and for each sub-account I call myself, appending responses to the list of mortgage details in the final response.

The end result, is a response structure with nested mortgage details.

Let’s start by taking a look at the assembly diagram:

The MortgageAccount untyped component represents the back-end. I will be manually emulating this, so an untyped component will suffice.

RetrieveMortgageDetails is a BPEL microflow which references the back-end mock and also references itself.

I’ve implemented two interfaces, one for the microflow and another one for the mock back-end.

Both interfaces have a message input with a mortgage account Id but the response objects are slightly different.

The microflow returns a MortgageDetails object, which has as an attribute a list of MortgageDetails, as follows:

The mock back-end returns a MortgageAccount object, which has as an attribute a list of sub-account Ids:

The microflow is implemented as follows:

The first invoke calls the back-end, then for each sub-account Id in the response I call myself, appending the response to the subAccount attribute in my response to the calling client. Of course the ‘calling client’ will be myself when traversing the nested sub-accounts, and the real client once all sub-accounts are retrieved.

Here’s the result of a test run:

You can see how the response has a main mortgage account (id 1) which has two sub-accounts (1.1 and 1.2) You can also see that sub-account 1.1 has two nested sub-accounts (1.1.1 and 1.1.2)

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About Gabriel Telerman
Occupation: IBM SOA-BPM Consultant. Profession: Guitar Hero

2 Responses to SCA Recursion

  1. Pattabi says:

    Thanks for sharing very informative tips. I am just starting on WPS. Found this and the Store & Forward very useful. It’s like doing a crash course.

  2. Gabriel Telerman says:

    Thanks Pattabi, glad you find it useful. A PI for this can be downloaded here: http://dl.dropbox.com/u/7924702/RecursionPI.zip

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