Question

If I have a base class such that

public abstract class XMLSubscription <T extends XMLMessage> 

Is it possible to write a method in XMLSubscription that returns a class object of T?

The only possible solution that I came up with is to have each descendant of XMLSubscription have a method like:

public class XMLStatusSubscription extends XMLSubscription<XMLStatusMessage> {    public Class <XMLStatusMessage> getExpectedMessageType()    {              return XMLStatusMessage.class;    } } 

Answer 1

Unfortunately – and yes, this is due to type erasure – there is no way to return the Class object without providing it at runtime somehow.

Fortunately this is not usually too difficult. Here’s how I’ve typically done this / seen it done:

public abstract class XMLSubscription <T extends XMLMessage> {     private Class<T> messageType;      protected XMLSubscription(Class<T> messageType) {         this.messageType = messageType;     }      public Class<T> getExpectedMessageType() {         return this.messageType;     } }  public class XMLStatusSubscription extends XMLSubscription<XMLStatusMessage> {      public XMLStatusSubscription() {         super(XMLStatusMessage.class);     } }