How to HTTP POST a Flux<String> as a JSON array using Spring's WebClient?

Question

How do I use Spring's reactive WebClient to POST a Flux<String> as a JSON array?

Flux<String> stringFlux = Flux.fromIterable(objects).map(MyObject::getSomeString);

WebClient.create(baseUrl)
  .post()
  .uri(myUrl)
  .contentType(MediaType.APPLICATION_JSON)
  .body(stringFlux, String.class)
  .exchange()
  .flatMap(response -> {
     if (response.statusCode().is2xxSuccessful()) {
       // Do something
     }
     return response.bodyToMono(Void.class);
   })
   .block();

This sends the request, but it's not sending it as a JSON array of strings.

I saw that there's another body() signature that accepts a ParameterizedTypeReference, so I tried this:

.body(stringFlux.collectList(), new ParameterizedTypeReference<>() {})

but this results in a compile error actually (I'm on Java 11):

Error:java: com.sun.tools.javac.code.Types$FunctionDescriptorLookupError.

Any ideas?

heez · Accepted Answer · 2019-01-14 18:45:32Z

4

Well I'll be darned. I got it working using ParameterizedTypeReference. As is usually the case, the compile error sums it up. I omitted the type parameter when declaring a new ParameterizedTypeReference<>() {}. Providing the type did the trick and posted my Flux<String> as a JSON array:

.body(stringFlux.collectList(), new ParameterizedTypeReference<List<String>>() {})

IntelliJ was telling me this type was inferred, but apparently it is not.

answered Jan 14, 2019 at 18:45

heez

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Saljack · Accepted Answer · 2020-05-13 21:28:57Z

0

You can do it without ParametrizedTypeRefrence using List.class is enough for Strings.

.body(stringFlux.collectList(), List.class)

answered May 13, 2020 at 21:28

Saljack

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Comments

Mureinik · Accepted Answer · 2021-08-28 01:12:14Z

0

.body(BodyInserters.fromFormData(stringFlux))

Not sure if this is the right answer. It works for me to send List<> as body

edited Aug 28, 2021 at 1:12

Mureinik

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answered Aug 27, 2021 at 20:56

Varun

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Stadmina · Accepted Answer · 2021-07-30 11:38:31Z

-1

The voted solution doesn't seem to produce the mentioned result. This seems to stream a list of JSON objects (which is what Webclient is intended for) rather than sending a JSON Array structure. the result I get with that technic is :

{}{}{}{}

A JSON Array output would be:

[{}, {}, {}, {}]

Unless I'm missing something.

answered Jul 30, 2021 at 11:38

Stadmina

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1 Comment

matt forsythe Jan 10 at 5:24

This is not an answer - this should be posted as a comment to the voted solution.

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