JAVA OkHTTP3 Library gives me a 415 HTTP Error

Question

I have found a solution to solve this issue.

Check the first answer to this topic

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I've a problem with the library OkHTTP3. I want to join an API endpoint with the library.

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Firstly, I've created my request with Postman to test the API endpoint. After configuring the URL, the access token and the JSON Body, I've launched my request. Postman gived me a positive response (JSON response + HTTP Code 200). All works fine.

After that, I've coded my Java method. The first request to get the access token works fine.
But the second request return me a 415 HTTP Code. When I dump the JSON body given to the JAVA request and I paste it into Postman, I don't have any problem.

Also, the headers between my JAVA method with OkHTTP3 and my Postman configuration are litterally the same... I don't know why it doesn't work !

Below, my JAVA code and a screen capture of my Postman configuration.
If anyone has an idea... thanks in advance !

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public static void getAlertModels(OAuthToken oAuthToken, int customerId) throws IOException {

    ApiRequest apiRequest = new ApiRequest(
        new ApiRequestSearch(
            Arrays.asList("triggers", "customers"),
            Arrays.asList(
                Arrays.asList("product"),
                Arrays.asList(9)
            )
        )
    );
    
    ObjectMapper objectMapper = new ObjectMapper();

    String jsonBody = objectMapper.writeValueAsString(apiRequest);

    OkHttpClient client = new OkHttpClient().newBuilder().build();

    MediaType mediaType = MediaType.parse("application/json");

    RequestBody body = RequestBody.create(jsonBody, mediaType);

    Request request = new Request.Builder()
        .url("https://api.anonymous.tld/alertModels")
        .method("POST", body)
        .addHeader("Authorization", "Bearer " + oAuthToken.getAccessToken())
        .addHeader("Content-Type", "application/json")
        .addHeader("Accept", "application/json")
        .build()
    ;

    Response response = client.newCall(request).execute();

    System.out.println(jsonBody);
    System.out.println(response.code());
    System.out.println(response.body().string());
}

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Postman Body Configuration : https://i.stack.imgur.com/YFOXV.png
Postman Headers Configuration : https://i.stack.imgur.com/7cBI7.png

Answer 1

So, I have finally found a solution to solve this problem.

For all people who use the OkHttp3 library, when you build the RequestBody object, you specify the RequestBody and the MediaType like that :

MediaType mediaType = MediaType.parse("application/json");

RequestBody body = RequestBody.Companion.create(jsonBody, mediaType);

Request request = new Request.Builder()
    .url("https://api.anonymous.tld/alertModels")
    .post(body)
    .addHeader("Authorization", oAuthToken.getAccessToken())
    .build()
;

The MediaType.parse(...) method concat charset=utf-8 to the Content-Type.
Some API doesn't accept header like that : Content-Type: application/json; charset=utf-8 but accept that : Content-Type: application/json

So, remove the MediaType object, create the RequestBody without the MediaType and specify the Content-Type into the Request.Builder() method. The final code looks like that :

// Remove the below line
// MediaType mediaType = MediaType.parse("application/json");

// Set the second parameter to "null"
RequestBody body = RequestBody.Companion.create(jsonBody, null);

// Add a new header with the desired Content-Type
Request request = new Request.Builder()
    .url("https://api.anonymous.tld/alertModels")
    .post(body)
    .addHeader("Authorization", oAuthToken.getAccessToken())
    .addHeader("Content-Type", "application/json")
    .build()
;

For more informations, you can referer to the discussion of the following GitHub issue : https://github.com/square/okhttp/issues/3081