jpa - Spring data Pageable and LIMIT/OFFSET

Question

i'm looking at migrating our traditional jpa/dao solution to Spring Data.

However, one of our front-ends is SmartGWT, and their databound components load data progressively using limit/offset only, making it hard to use Pageable.

This causes problems, since it's not certain that the limit/offset can be translated evently into a page number. (it might differ depending on how the user scrolls, screen is resized etc.).

I looked at Slice etc, but wasn't able to find a way to use the limit/offset values anywhere.

Was wondering if someone has any pointers? Optimally i would like to continue using limit/offset, but use them in my Repository interfaces without having to code an implementation and set them manually like i do now (query.setMaxResults etc.)

Edit: To clarify why i have issues - The limit/offset might differ between the initial and subsequent data fetches in a smartgwt component. For a listgrid, the first fetch might have limit set to 89 for example, since that's the amount of rows visible on screen, and offset 0. The next request, though, might have offset 89, and limit 50 since that's the component's "datapagesize" value to 50, so that's what it'll fetch when i scroll down. If i scroll to far down before releasing, it might, depending on the settings, fetch for example rows 159-209 instead. Basically, there's no guarantee that the offset is a multiple of anything. It's hard to convert offset 17, limit 5 to a page.

Answer 1

Pagebale implementations do use limit and offset to create pagination. The page value in the constructor is used to generate the offset value in the AbstractPageRequest class getOffset method:

public int getOffset() {
    return this.page * this.size;
}

If you want to only use limit and offset and discard the page parameter from the mix, take a look at the Spring Data documentation on web support, particularly the part about overriding the default configuration. You could create your own implementation of Pageable that takes limit and offset as constructor arguments and the implement your own HandlerMethodArgumentResolver to replace the standard PageRequest resolving. Quick-and-dirty example:

Pageable implementation

public class BetterPageRequest implements Pageable {

    public BetterPageRequest(int limit, int offset){
        this.limit = limit;
        this.offset = offset;
    }

    // Other method implementations

}

HandlerMethodArgumentResolver implementation

public class BetterPageableResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter){
        return Pageable.class.equals(parameter.getParameterType());
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer container, NativeWebRequest request, WebDataBinderFactory factory){
        Map<String,String[]> params = request.getParameterMap();
        return new BetterPageRequest(params.get('limit')[0], params.get('offset')[0]);
    }

}