Send JSON body in HTTP GET request in java/spring boot

Question

I need to send a GET request with a json body in java/spring boot. I'm aware of the advice against it, however I have to do it this was for a couple of reasons: 1. The 3rd party API I'm using only allows GET requests, so POST is not an option. 2. I need to pass an extremely large parameter in the body (a comma separated list of about 8-10k characters) so tacking query params onto the url is not an option either.

I've tried a few different things:

1. apache HttpClient from here: Send content body with HTTP GET Request in Java. This gave some error straight from the API itself about a bad key.

2. URIComponentsBuilder from here: Spring RestTemplate GET with parameters. This just tacked the params onto the url, which as I explained before is not an option.

3. restTemplate.exchange. This seemed the most straightforward, but the object wouldn't pass: https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.lang.String-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-java.lang.Class-java.util.Map-

as well as probably another thing or two that I've forgotten about.

Here is what I'm talking about in Postman. I need to be able to pass both of the parameters given here. It works fine if run through Postman, but I can't figure it out in Java/Spring Boot.

Here is a code snippet from the restTemplate.exchange attempt:

public String makeMMSICall(String uri, List<String> MMSIBatchList, HashMap<String, String> headersList) {
    ResponseEntity<String> result = null;
    try {
        RestTemplate restTemplate = new RestTemplate();

        HttpHeaders headers = new HttpHeaders();
        for (String key : headersList.keySet()) {
            headers.add(key, headersList.get(key));
        }

        Map<String, String> params = new HashMap<String, String>();
        params.put("mmsi", String.join(",", MMSIBatchList));
        params.put("limit", mmsiBatchSize);

        HttpEntity<?> entity = new HttpEntity<>(headers);
        result = restTemplate.exchange(uri, HttpMethod.GET, entity, String.class, params);

        System.out.println(result.getBody());

    } catch (RestClientException e) {
        LOGGER.error("Exception in makeGetHTTPCall :" + e.getMessage());
        throw e;
    } catch (Exception e) {
        LOGGER.error("Exception in makeGetHTTPCall :" + e.getMessage());
        throw e;
    }
    return result.getBody();
}

Thanks for helping!

Answer 1

You can try java.net.HttpUrlConnection, it works for me but indeed I normally use a POST

HttpURLConnection connection = null;
BufferedReader reader = null;
String payload = "body";

try {

    URL url = new URL("url endpoint");

    if (url.getProtocol().equalsIgnoreCase("https")) {
        connection = (HttpsURLConnection) url.openConnection();
    } else {
        connection = (HttpURLConnection) url.openConnection();
    }
    //  Set connection properties
    connection.setRequestMethod(method); // get or post
    connection.setReadTimeout(3 * 1000);
    connection.setDoOutput(true);
    connection.setUseCaches(false);        

    if (payload != null) {
        OutputStream os = connection.getOutputStream();

        os.write(payload.getBytes(StandardCharsets.UTF_8));

        os.flush();
        os.close();
    }

    int responseCode = connection.getResponseCode();
}

Answer 2

There's no way of implementing it via RestTemplate, even with .exchange method. It'll simply not send the request body for GET calls even if we pass the entity within the function parameters.(Tested via interceptor logs)

You can use the Apache client to solve this issue/request (whatever you'd like to call it). The code you need is something along following lines.

  private static class HttpGetWithBody extends HttpEntityEnclosingRequestBase {

    JSONObject requestBody;

    public HttpGetWithBody(URI uri, JSONObject requestBody) throws UnsupportedEncodingException {
      this.setURI(uri);
      StringEntity stringEntity = new StringEntity(requestBody.toString());
      super.setEntity(stringEntity);
      this.requestBody = requestBody;
    }

    @Override
    public String getMethod() {
      return "GET";
    }
  }


  private JSONObject executeGetRequestWithBody(String host, Object entity) throws ClientProtocolException, IOException {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    try{
      JSONObject requestBody = new JSONObject(entity);
      URL url = new URL(host);
      HttpRequest request = new HttpGetWithBody(url.toURI(), requestBody);
      request.addHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
      request.addHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE);
      HttpResponse response;
      if(url.getPort() != 0) response = httpClient.execute(new HttpHost(url.getHost(), url.getPort()), request);
      else response = httpClient.execute(new HttpHost(url.getHost()), request);

      if(response.getStatusLine().getStatusCode() == HttpStatus.SC_OK){
        JSONObject res = new JSONObject(EntityUtils.toString(response.getEntity(), StandardCharsets.UTF_8));
        httpClient.close();
        return res;
      }
    }catch (Exception e){
      log.error("Error occurred in executeGetRequestWithBody. Error: ", e.getStackTrace());
    }
    httpClient.close();
    return null;
}

If you inspect even Apache client library doesn't support passing the body natively(checked via code implementation of HttpGet method), since contextually request body for a GET request is not a good and obvious practice.

Answer 3

Try creating a new custom RequestFactory. Similar to get request with body