Why are Maps returned by a JAX-WS call always empty?

Question

My web service method returns a Page object which includes the following methods:

public Map<String,String[]> getParameters() { ... }
public setParameters(Map<String,String[]> parameters) { ... }

On the client side, the JAX-WS generated getParameters() method returns a Parameters object which provides a getEntry() method that returns a List<Entry>. However, this list is always empty. What is the cause?

Answer 1

You have to use concrete types instead of interfaces in setters and getters:

public HashMap<String,String[]> getParameters() { ... }
public setParameters(HashMap<String,String[]> parameters) { ... }

Then, everything works as expected.