Others may be able to provide examples.
1) Is it possible to use a JSR step, Request/Response-Side Scriptable or Custom DPH in the VSM to implement logic to generate and store a value in testExec? For example:
<addPersonResponse>
<status>SUCCESS</ns0:status>
<personId>123456</personId>
<uniqueId>{{myNewField}}</uniqueId>
So long as myNewField is created prior to the Response step, the value should be able to substitute.
2) Invoke a Static method on a class. For example:
The response body, can contain something like this:
<addPersonResponse>
<status>SUCCESS</ns0:status>
<personId>123456</personId>
<uniqueId>{{=java.util.UUID.randomUUID().toString();}}</uniqueId>
The result is a response that looks like this:
<addPersonResponse>
<status>SUCCESS</status>
<personId>123456</personId>
<uniqueId>9a8f11ce-8eaa-478a-9e3a-4c58a5754f3c</uniqueId>
3) (Caveat: I have not tried this) If one had a custom class / method that returns a string, you might:
<uniqueId>{{=com.ca.MyClass.someMethod(lisa_vse_request);}}</uniqueId>
someMethod's signature accepts com.itko.lisa.vse.stateful.model.Request; thereby giving access to all of the methods on the lisa_vse_request object as well as other classes.