Showing a paged list of spittles

As next step in our little Spring Web App, we are going to add in the view a way to display spittles specifying the "end" id, using the standard convention that it is excluded from the interval, and how many of them we want to show.

To do that, I firstly change the SpittleController so that its method mapped to the GET request method would accept the two parameters, giving them default values so that the previous functionality still works.

@RequestMapping(method = RequestMethod.GET)
public List<Spittle> spittles(
        @RequestParam(value = "max", defaultValue = MAX_ID) long max,
        @RequestParam(value = "count", defaultValue = DEFAULT_COUNT) int count) {
    return spittleRepository.findSpittles(max, count);
}

Actually, this version looks quite different from the previous one. The return value here is a List of Spittles, the one that was put in the spittleList model, and so we should wonder how Spring could guess which JSP call to generate a view.

However, internally, they are equivalent - if we don't consider how findSpittles() is called. The job of generating the JSP page and the attribute name is done by the mighty Spring framework, that understands that the first should be extracted from the URI passed as string to the class RequestMapping annotation, "/spittles", stripping the leading slash, and builds the latter from the method return type.

Just a minor nuisance. As the Java compiler states, "The value for annotation attribute RequestParam.defaultValue must be a constant expression". So I can't define MAX_ID converting on the fly the Long.MAX_VALUE to a String:

private static final String MAX_ID = Long.toString(Long.MAX_VALUE); // WON'T WORK!

I have to operate the conversion "by hand", instead.

private static final String MAX_ID = "9223372036854775807"; // Boring!

Besides the already existing shouldShowRecentSpittles() test, that should still work, I added a new shouldShowPagedSpittles() test that is very close to the other one but passes parameters to the (mock) call to the controller. See the tester on GitHub for more details.

Given the fake implementation I gave to the JdbcSpittleRepository, I can also see a result from the browser.

Reference: Accepting request input, from Spring in Action, Fourth Edition by Craig Walls. Chapter five, section three.

Full code for this Spring project is on GitHub.