Polymorphism in JAX-RPC web services
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.
Asked by: Adrian425 | Posted: 21-01-2022
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.
Answered by: Freddie957 | Posted: 22-02-2022Answer 2
Maybe someone is still looking for it, it can be done in axis 1.4:
Add next line into your section of axis web service deployment file (wsdd):
<parameter name="emitAllTypesInWSDL" value="true" />Modify your task in ant build file to include 'extraClasses':
<axis-java2wsdl ... extraClasses="..."></axis-java2wsdl>In extraClasses mention all classes which will be passed, since axis aren't able to guess which childs you'll be passing/returning as parameters.
Done, now you can pass derivated classes in methods accepts parent classes. Etc:
// server side class A { ...}
class B extends A {...}
class C extends A {...}
// ws
class wsAxis { public void processPolymorphCall(A obj); }
// client side
wsAxis.processPolymorphCall(new C());
// this will work now, as much as returning derivated classes in place of base class.
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