Question

I am kind a confuse on the implementation i am working on. This the method which i am suppose to call

<I, O, T> T post(String url, I data, ContentBuilder<I, HttpEntity> contentBuilder, ResponseHandler<? extends T> responseHandler);

Now i have to write couple of classes which will be used for ContentBuilder and responsehandler. the thing to be noticed is return type T.

I wrote an abstract class WSResponse and then extended it MyWSResponse so that my response handler looks like

ResponseHandler <WSResponse> rh = new MyWSResponse();

The method which is calling this post method has this signature

public interface GPCl{
   public <T> T callPost (String data)
}

…

public <T> T callPost(String data){
    HttpWebServiceClient client = getHttpWSClient();
    ContentBuilder<String, HttpEntity> contentBuilder = new MyXMLBuilder();
    ResponseHandler<WSResponse> rh= new MyWSResponse();

    WSResponse wsResponse = client.post("", data, contentBuilder, rh);
    return (T)wsResponse;
}

Now i am confused at return type of this method. Would it remain T or something else? If i change it from T to WSRespons, i get an error that i haven’t implemented method callPost.

The method callPost is being called as

GPClient cl = new GPClient(myhttpParams);
cl.callPost(d)

P.S:
this is first time i am dealing with generics

Answer 1

Methods of this type — <T> T method(things that don't mention T) — are almost never what you want to do, and are highly dangerous, because they inevitably involve casts that probably don’t work — but you won’t be warned until it fails at runtime. I suspect that the return type of this method should just be WSResponse, but your question isn’t clear enough for me to be sure.