How to make a POST request using retrofit 2?

Question

I was only able to run the hello world example (GithubService) from the docs.

The problem is when I run my code, I get the following Error, inside of onFail

Answer 1

If you don't want JSON encoded params use this:

@FormUrlEncoded
@POST("/")
Call<ApiResponse> request(@Field("api_key") String apiKey, @Field("app_id") String appId);

Answer 2

You should be aware of how you want to encode the post params. Important is also the @Header annotation in the following. It is used to define the used content type in the HTTP header.

@Headers("Content-type: application/json")
@POST("user/savetext")
    public Call<Id> changeShortText(@Body MyObjectToSend text);

You have to encode your post params somehow. To use JSON for transmission you should add .addConverterFactory(GsonConverterFactory.create(gson)) into your Retrofit declaration.

Retrofit restAdapter = new Retrofit.Builder()
                .baseUrl(RestConstants.BASE_URL)
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(httpClient)
                .build();

Another source of your problem could be that the JSON, that's coming from the rest backend seems to be not correct. You should check the json syntax with a validator, e.g. http://jsonlint.com/.