What design pattern is this - Adapter, Provider, Delegate, Template Methods, or ...?

Question

Here's a simple design patterns question:

As part of my current project, I have written an interface that performs a database search (using webservices and relevant client stubs) and returns the results - which will be used subsequently by a struts action as a response to a JSON request.

The interface is something like this:

    public interface DynamicSearchProvider {

        JSONObject getSearchResultsAsJSONObject(DatatablesRequestParams params) 
                throws JSONException;

    }

and then for each specific type of object, a concrete version of the above will be implemented so that it will call the relevant web services and returns a result.

Basically, it's just wrapper around a bunch of business logic as far as I can tell.

The question is, what would you call this? I don't like the term provider as it's quite ambiguous. Is there a well defined design pattern for this?

Ideally I would have preferred to use Spring with this by the way but unfortunately I can't in this project as it's part of a legacy code base...

EDIT:

Here's where it gets used:

public abstract class GenericDynamicSearchAction extends GenericAction {

    private static Log log = LogFactory.getLog(GenericDynamicSearchAction.class);

    /**
     * Method to be implemented by each individual search action
     */
    public abstract DynamicSearchProvider getDynamicSearchProvider();

    public final ActionForward executeAuthenticated(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws IOException {

        log.debug("called");

        DatatablesRequestParams datatablesRequestParams = DatatablesUtils.extractDatatablesParamsFromRequest(request);

        try {


            JSONObject jsonResponse = getDynamicSearchProvider().getSearchResultsAsJSONObject(datatablesRequestParams);

            String echo = datatablesRequestParams.getEcho();

            jsonResponse.put(DatatablesUtils.ECHO_FIELD_NAME, echo);
            response.setContentType("application/json");

            String jsonResponseString = jsonResponse.toString();

            log.debug("Returning JSON response:"+jsonResponseString);

            response.getWriter().print(jsonResponseString);

        } catch (JSONException e) {

            response.setContentType("text/html");
            response.getWriter().print(e.getMessage());

        }

        return null;

    }

etc...

So, for a specific type of object, a concrete version of the above Action class (it's stuts action by the way) is implemented, and it will have a reference to an implementation of the above "Provider"... like this:

public class PolicyDynamicSearchAction extends GenericDynamicSearchAction {

    @Override
    public final DynamicSearchProvider getDynamicSearchProvider() {

        return new PolicyDynamicSearchProvider();

    }
}

and

public class PolicyDynamicSearchProvider implements DynamicSearchProvider {

    public final JSONObject getSearchResultsAsJSONObject(DatatablesRequestParams params) throws JSONException {
//some business logic that goes to webservice etc to get the info
}
}

Hope it makes it clearer.

add more code because it is difficult to tell what it is for sure — Yurii Hohan, Oct 13 '11 at 13:56
It's really as simple as above, it just takes a request parameter object and returns a JSON object, depending on implementation it will call different web services and returns different CONTENTS in JSON object. — Ashkan Aryan, Oct 13 '11 at 14:01
I am pretty sure it's not Adapter, nor a Provider, might be Delegate because your action class delegates searching to this. — Bhesh Gurung, Oct 13 '11 at 14:02
Looks like a not-so-correctly-implemented Decorator pattern too me. — Perception, Oct 13 '11 at 14:03
What you describe reminds of strategy pattern but again I do not see the code — Yurii Hohan, Oct 13 '11 at 14:05
Hohhi is right. I think it does not make any sense to look for a Design Pattern in just one interface. — Bhesh Gurung, Oct 13 '11 at 14:09
I consider it a strategy pattern. Why do you think that the choice is compile time? — Yurii Hohan, Oct 13 '11 at 14:13
@Perception, don't think so, doesn't fit decorators description, I think it's Template Method exactly as binary_runner mentions below — Ashkan Aryan, Oct 13 '11 at 14:45

score 2 · Accepted Answer · answered Oct 13 '11 at 14:03

2

Guessing from you "bunch of business logic" it is a Facade. Still, IMHO naming classes after the design pattern is not a good idea generally. First, class can implement several design patterns at once, second this approach is hard to maintain during refactorings.

I think it is especially wrong idea with the facade, as it the caller should not be aware of the fact that the method works as facade.

Provider sounds good, but DynamicSearchService sounds better to me.

answered Oct 13 '11 at 14:03

Rostislav Matl

4,294
4
29
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Thanks, I'm not too bothered to name it after the pattern, just want to know what I am doing and whether it fits into a pattern. – Ashkan Aryan Oct 13 '11 at 14:05
Facade wraps a whole subsystem with a lot of tangled calls and does not allow calling the insides of it. This seems to not be the case – Yurii Hohan Oct 13 '11 at 14:07
No, your definition of facade is too narrow. – Rostislav Matl Oct 13 '11 at 14:11
@binary_runner yes I thought of "...Service" too, makes sense, that's what it does after all, "provide"s a business "service"... – Ashkan Aryan Oct 13 '11 at 14:26
1

As for your added example - the GenericDynamicSearchAction class represents Template Method pattern. – Rostislav Matl Oct 13 '11 at 14:26
@binary_runner so it is! nice one, thanks! With references to IOC etc in the article in Wikipedia - makes sense now and I understand why I was thinking Spring would've been useful here! – Ashkan Aryan Oct 13 '11 at 14:40
If you're satisifed with my answer, don't forget to accept it :). – Rostislav Matl Oct 13 '11 at 14:44

score 0 · Answer 2 · answered Oct 13 '11 at 14:03

0

This isn't my area of expertise but I think it sounds like the Strategy pattern

answered Oct 13 '11 at 14:03

danseagrave

328
5
12

The choice of the concrete class is done at compile time not run time so it probably isn't a strategy pattern... – Ashkan Aryan Oct 13 '11 at 14:06
Why do you do it at compile-time? Are there any if-s? – Yurii Hohan Oct 13 '11 at 14:07

What design pattern is this - Adapter, Provider, Delegate, Template Methods, or ...?

2 Answers2