Could not write request: no suitable HttpMessageConverter found for request type [org.json.JSONObject] and content type [application/json]

Question

I\'m digging myself in trying to send a POST request with a JSON payload to a remote server.

This GET curl command works fine:

curl -H \"Accept:appli         


        

Answer 1

I had to do a few things to get this working.

First I had to convert the JSONObject to a string, as in:

HttpEntity entityCredentials = new HttpEntity(jsonCredentials.toString(), httpHeaders);

The reason being that there is no mapping message converter for the JSONObject class while there is one for the String class.

Second I had to pass a true value to the RestTemplate constructor. Failing to do so, I would get a 400 Bad Request.

RestTemplate restTemplate = new RestTemplate(true);

The true value tells the rest template to use the default converters. If someone knows why this is so, I'd be happy to know more about.

Third I removed the unneeded Jackson converter:

restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());

With these things done, the request works just fine.

Here is the full code:

RestTemplate restTemplate = new RestTemplate(true);    
User user = null;
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentType(MediaType.APPLICATION_JSON);
httpHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
try {
    JSONObject jsonCredentials = new JSONObject();
    jsonCredentials.put("email", REST_LOGIN);
    jsonCredentials.put("password", REST_PASSWORD);
    Log.e(Constants.APP_NAME, ">>>>>>>>>>>>>>>> JSON credentials " + jsonCredentials.toString());
    HttpEntity entityCredentials = new HttpEntity(jsonCredentials.toString(), httpHeaders);
    ResponseEntity responseEntity = restTemplate.exchange("http://" + REST_HOST + ":" + REST_PORT + "/" + REST_APP + "/api/users/login",
            HttpMethod.POST, entityCredentials, User.class);
    if (responseEntity != null) {
        user = responseEntity.getBody();
    }
    return user;
} catch (Exception e) {
    Log.e(Constants.APP_NAME, ">>>>>>>>>>>>>>>> " + e.getLocalizedMessage());
}
return null;

I suspect there could be a way to explicitly use a Jackson converter and skip the true value in the rest template constructor, but this is just a guess.