[FIXED] How to avoid double-encoding of [] when using Spring RestTemplate?

Issue

I've a Spring Boot 2.2.5 application calling this REST endpoint

@RequestMapping(path = "/usable/search")
public List<Provider> findUsable(
      @RequestParam(name = "country-id", required = false) Integer countryId,
      @RequestParam(name = "network-ids[]", required = false) List<Integer> networkIds,
      @RequestParam(name = "usages[]") Set<Usage> usages)

My caller does

val url = clientUri.toString() + configuration.getUrl().getUseableProvidersForNetworks(); % 'providers/usable/search?'
val builder = UriComponentsBuilder.fromHttpUrl(url)
      .queryParam("usages[]", USAGES)
      .queryParam("network-ids[]", networkIds);
val response =
      restTemplate.exchange(
          builder.toUriString(),
          HttpMethod.GET,
          entity,
          new ParameterizedTypeReference<List<Provider>>() {});

where USAGES is a Set<Usage> and networkIds is a List<Integer>.

The RestTemplate is created by

RestTemplate eurekaRestTemplate() {
    val requestFactory = new HttpComponentsClientHttpRequestFactory();
    requestFactory.setReadTimeout(TIMEOUT);
    requestFactory.setConnectTimeout(TIMEOUT);
    return new RestTemplate(new BufferingClientHttpRequestFactory(requestFactory));
  }

Problem: The [] get double encoded to %255B%255D and I end up with a call to

providers/usable/search?usages%255B%255D=MESSAGE_DELIVERY&network-ids%255B%255D=2145118475&network-ids%255B%255D=-1536358371

Which obviously doesn't work; the server misses e.g. usages[]. It works with curl with [] instead of %255B%255D.

How can I avoid that?

I'm aware of this issue and the docs, but that didn't help yet.

Solution

The solution was to call UriComponentsBuilder.build(false) to instruct the UriComponentsBuilder not to encode the url:

val response = restTemplate.exchange(
              builder.build(false).toUriString(),
              HttpMethod.GET,
              entity,
              new ParameterizedTypeReference<List<Provider>>() {});

This is tricky because a test with Mockito/JUnit of this will tell you that the url is not encoded while a test with MockRestServiceServer will show one level of encoding ([] become %5B%5D).

Answered By - Martin Schröder
Answer Checked By - David Marino (JavaFixing Volunteer)