Rest Web Service using Interfaces - web-services

Question

I am trying to create a REST web-service in Java using RestEasy with the design similar to the example classes that I have shown below:
#Path("/rest")
public class TestRestService {
#GET
#Path("/test")
#Produces("application/xml")
public Response sayTestXml() {
return getImplementation();
}
public Response getImplementation() {
IInterface refToImpl = TestService.getImplementation();
return Response.status(Status.OK).entity(refToImpl).build();
}
}
public class TestService {
public static IInterface getImplementation() {
IInterface ref = new Implementation();
return ref;
}
}
public interface IInterface {
public long getLong();
public String getString();
public boolean getBoolean();
public List<IRelatedInterface> getRelations();
}
public interface IRelatedInterface {
public float getFloat();
public char getChar();
public byte getByte();
}
#XmlRootElement(name="interface")
#XmlAccessorType(XmlAccessType.PROPERTY)
public class Implementation implements IInterface {
#XmlElement(name="tlong", required=true)
public long getLong() {
return 42;
}
#XmlElement(name="tstring", required=true)
public String getString() {
return "test";
}
#XmlElement(name="tboolean", required=true)
public boolean getBoolean() {
return false;
}
#XmlElementWrapper(name = "relations")
#XmlElement(name = "relation", required=false)
public List<IRelatedInterface> getRelations() {
List<IRelatedInterface> list = new ArrayList<IRelatedInterface>();
RelatedImplementation impl = new RelatedImplementation();
list.add(impl);
return list;
}
}
#XmlRootElement(name="relatedInterface")
#XmlAccessorType(XmlAccessType.PROPERTY)
public class RelatedImplementation implements IRelatedInterface {
#XmlElement(name="tfloat", required=true)
public float getFloat() {
return 1.23f;
}
#XmlElement(name="tchar", required=true)
public char getChar() {
return 'A';
}
#XmlElement(name="tbyte", required=true)
public byte getByte() {
return 'Z';
}
}
So, when I try this design then JAXB complains as below:
com.sun.xml.bind.v2.runtime.IllegalAnnotationsException:
2 counts of IllegalAnnotationExceptions com.intuit.whitespace.IRelatedInterface is an interface, and JAXB can't handle interfaces.
this problem is related to the following location: at com.intuit.whitespace.IRelatedInterface at public java.util.List com.intuit.whitespace.Implementation.getRelations() at com.intuit.whitespace.Implementation com.intuit.whitespace.IRelatedInterface does not have a no-arg default constructor. this problem is related to the following location: at com.intuit.whitespace.IRelatedInterface at public java.util.List com.intuit.whitespace.Implementation.getRelations() at com.intuit.whitespace.Implementation
My question is, is there a way to solve this? I have tried some things but none of them have worked. I am considering Spring OXM or a MessageBodyWriter based solution, but I wanted to ask if there were any other suggestions that would help me better?

Answer 1

Okay, I solved it by making the following changes:
Used the type attribute in #XmlElement
public class Implementation implements IInterface {
#XmlElementWrapper(name = "relations")
#XmlElement(name = "relation", required=false, type=RelatedImplementation.class)
public List<IRelatedInterface> getRelations() {
....
}
}
That is all!