How process CompletionStage with spring?

Question

How configure spring to work with CompletionStage return types? Consider a code:

@RequestMapping(path = "/", params = "p", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public CompletionStage<List<MyResult>> search(@RequestParam("p") String p) {
    CompletionStage<List<MyResult>> results = ...
    return results;
}

I got 404, but I see in log that method is triggered. If I change signature like that:

@RequestMapping(path = "/", params = "p", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public List<MyResult> search(@RequestParam("p") String p) {
    CompletionStage<List<MyResult>> results = ...
    return results.get();
}

I see successfull json array.

How to make CompletionStage works with spring (4.2.RELEASE)?

UPDATED

For test I wrote following methods:

@RequestMapping(path = "/async")
@ResponseBody
public CompletableFuture<List<MyResult>> async() {
    return CompletableFuture.completedFuture(Arrays.asList(new MyResult("John"), new MyResult("Bob")));
}

And it works. Oo

I have test this version of future:

@RequestMapping(path = "/async2")
@ResponseBody
public CompletableFuture<List<MyResult>> async2() {
    AsyncRestTemplate template = new AsyncRestTemplate();
    //simulate delay future with execution delay, you can change url to another one
    return toCompletable(template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(
                    resp -> template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(
                    resp -> template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(
                    resp -> template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(
                    resp -> template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(
                    resp -> template.getForEntity("https://www.google.ru/?gws_rd=ssl#q=1234567890-", String.class))
            .thenApply(resp -> Arrays.asList(new MyResult("John"), new MyResult("Bob")));
}

A bit agly, but ... works!

So my original method has the following logic:

Iterate over Collection
Make async call via AsyncRestTemplate for each collection element
Make call to each CompletableFuture in collection
- thenApply (transform result)
- thenCompose (make new async call with AsyncRestTemplate)
- thenApply (transform result)
- At the end I call transform List to Completable as described here.

It seem that Future transformation is wrong. Can it be that future chain eecutes too long? Any ideas?

That should be available by default. Post the error / logs you get on the server. (As an edit not as comments!). — M. Deinum, Sep 14 '15 at 11:23
Updated. There are no erros in logs, but I have done some experiments, may it helps. — Cherry, Sep 14 '15 at 13:13

score 0 · Answer 1 · answered Sep 14 '15 at 15:44

The problem was in that line:

@RequestMapping(path = "/" ...

When changed it to

@RequestMapping(path = "/1" ...

Future completion suddenly become working.

P.S. I had broken all my mind before found that the problem actually in the mapping. May helps for someone O:-)

How process CompletionStage with spring?

1 Answers1