Question

I have a JAX-RPC (Java) web service that needs to return a complex polymorphic value. To be more specific, the class structure is something like this:

abstract class Child { }  class Question extends Child {     private String name;     // other fields, getters, and setters }  class Section extends Child {     private String label;     private Child[] children;     // getters and setters }  class Quiz {     private Child[] elements;     // getter and setter } 

My web service has a method that returns a Quiz, which of course may contain Questions and Sections which may contain Questions and other Sections, and so on and so forth. However, when I generate the WSDL, only Child and Quiz make it in. When I call the web service, I get back a Quiz element with the right number of children, but they’re all Child elements, and they’re all empty.

Is there a good way to make this work, short of just returning XML as a String?

Before anyone asks, due to circumstances beyond my control, I cannot use JAX-WS.

Answer 1

I don’t think JAX-RPC supports polymorphism in that way. I had a similar problem, and had to work around it by creating a class that had just two members – one for each of the two classes that could possibly be returned – and only populating one depending on the type I wanted to return. So in your case:

class Child  {     private Section section;     private Question question;     // Constructor, etc... }  class Question  {     private String name;     // other fields, getters, and setters }  class Section  {     private String label;     private Child[] children;     // getters and setters }  class Quiz  {     private Child[] elements;     // getter and setter } 

Which requires the client to check which member of child is populated, and is horribly ugly, I know.