Spring 分页和计数查询

Question

I'm developping a REST API managing Module objects. For the UI, I need pagination and the total number of pages.

I know when Spring uses Page<T> an additional count query is used (to get the total number of pages) which is an overhead cost.

I need this total number of pages for the UI. But only once (no need to execute again the count query for each new page).

So I was thinking of exposing two endpoints:

• getting the total number of elements
• getting the data (so I'm returning a List<Module> instead of Page<Module> because I don't want to execute this extra count query for each page request)

Something like this:

@RestController

@RequestMapping("/api/modules")
public class ModuleApi {

    private final ModuleService service;

    @GetMapping("/count")
    public Long count() {
        return service.countModules();
    }


    @GetMapping
    public List<Module> find( 
                @RequestParam("name") String name ,
                @RequestParam(value = "page", required = false, defaultValue = "0") Integer page,
                @RequestParam(value = "size", required = false, defaultValue = "10") Integer size
    ) {
        return service.find(PageRequest.of(page, size));
    }
}

Is this a good design?

Answer 1

Counting once means your count will get outdated as more Modules are inserted into your database in which case the count is no longer relevant.

The better design would be to work with spring's Slice<Module> , forget the count altogether, and implement the solution on the front end side. Think of how some sites only fetch you more results when you are at the bottom of the page.

However this may cost a lot of effort and time on your architecture so your proposal should be fine.