How do I check if a view exists?

Question

I would like to check if a view exists before I actually resolve it. Here is my controller, with some comments on how I'd like it to work.

@RequestMapping(value="/somethinghere/")
    public String getSomething(Model inModel,
            @RequestParam(value="one", defaultValue=Constant.EMPTY_STRING) String one,
            @RequestParam(value="two", defaultValue = Constant.EMPTY_STRING) String two) {
        String view = one + two;
         if (a view with name equal to one + two exists) {
            return view;
        } else {
            return "defaultview";
        }                
}

I want to return a view, but only when I've verified that there is indeed a view with that name defined. How do I do this?

Answer 1

First, consider how view resolution is done in Spring. Assuming you are using a InternalResourceViewResolver, by default or explicit declaration, an InternalResourceView object created and the path to the resource is resolved by concatenating InternalResourceViewResolver's prefix, view name (returned by your hanbdler), and suffix.

That View object is returned. Note that with InternalResourceViewResolver that object cannot be null and therefore ViewResolver chaining cannot be achieved. The DispatcherServlet then uses the returned View object's render() method to create the HTTP response. In this case it will use a RequestDispatcher and forward to it the resource described by the View's name. If that resource doesn't exist, the Servlet container will produce a 404 response.

Given all that, unless your View is something completely different than a jsp or related resource, there's no way to check if the resource exists until the container actually forwards the request with a RequestDispatcher.

You will have to rethink your design.