android - Retrofit2: Modifying request body in OkHttp Interceptor

Question

I am using Retrofit 2 (2.0.0-beta3) with OkHttp client in Android application and so far everything going great. But currently I am facing issue with OkHttp Interceptor. The server I am communicating with is taking access token in body of request, so when I intercept the request to add auth token or in authenticate method of Authenticator when I need to add updated auth token, I need to modify body of request for this purpose. But it looks like I can only add data in headers but not in the body of ongoing request. The code I have written so far is as follows:

client.interceptors().add(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {
                Request request = chain.request();
                if (UserPreferences.ACCESS_TOKEN != null) {
                    // need to add this access token in request body as encoded form field instead of header
                    request = request.newBuilder()
                            .header("access_token", UserPreferences.ACCESS_TOKEN))
                            .method(request.method(), request.body())
                            .build();
                }
                Response response = chain.proceed(request);
                return response;
            }
        });

Can anyone point me to the right direction as how to modify request body to add my access token (first time or updated after token refresh)? Any pointer to right direction would be appreciated.

Answer 1

I using this to add post parameter to the existing ones.

 OkHttpClient client = new OkHttpClient.Builder()
                    .protocols(protocols)
                    .addInterceptor(new Interceptor() {
                        @Override
                        public Response intercept(Chain chain) throws IOException {
                            Request request = chain.request();
                            Request.Builder requestBuilder = request.newBuilder();
RequestBody formBody = new FormEncodingBuilder()
            .add("email", "Jurassic@Park.com")
            .add("tel", "90301171XX")
            .build();
                            String postBodyString = Utils.bodyToString(request.body());
                            postBodyString += ((postBodyString.length() > 0) ? "&" : "") +  Utils.bodyToString(formBody);
                            request = requestBuilder
                                    .post(RequestBody.create(MediaType.parse("application/x-www-form-urlencoded;charset=UTF-8"), postBodyString))
                                    .build();
                            return chain.proceed(request);
                        }
                    })
                    .build();

public static String bodyToString(final RequestBody request){
        try {
            final RequestBody copy = request;
            final Buffer buffer = new Buffer();
            if(copy != null)
                copy.writeTo(buffer);
            else
                return "";
            return buffer.readUtf8();
        }
        catch (final IOException e) {
            return "did not work";
        }
    }

OkHttp3:

RequestBody formBody = new FormBody.Builder()
                .add("email", "Jurassic@Park.com")
                .add("tel", "90301171XX")
                .build();