Send push notification via Firebase from android device

Question

I'm interested to send push notification via Firebase from android app. Firebase documentation states that payload json must be sent to https://fcm.googleapis.com/fcm/send

So I using with Retrofit to send a json but the request fails, and if I sending a request without Retrofit it's works perfect.

What's the difference between the tow implementations and why it's not works with Retrofit.

Here are the two implementations and the error when using Retrofit.

val notificationBody = NotificationBody(notificationData, "/topics/all")
    val rb = Gson().toJson(notificationBody).toRequestBody("application/json".toMediaTypeOrNull())
    val responeNoti = RetrofitManager.notificationServiceApi.postNotification(rb)
    responeNoti.enqueue(object : Callback<ResponseBody>{
        override fun onFailure(call: Call<ResponseBody>, t: Throwable) {
            Log.d(TAG, t.message)
        }

        override fun onResponse(call: Call<ResponseBody>, response: Response<ResponseBody>) {
            Log.d(TAG, response.toString())
        }

    })

NotificationServiceApi

 private const val FCM_URL = "https://fcm.googleapis.com/fcm/"
val notificationServiceApi: ServiceApi by lazy{
        val interceptor = HttpLoggingInterceptor()
        interceptor.level = HttpLoggingInterceptor.Level.BODY
        val okHttpClientBuilder = OkHttpClient.Builder()
        okHttpClientBuilder.addInterceptor(object : Interceptor{
            override fun intercept(chain: Interceptor.Chain): okhttp3.Response {
                val request: Request = chain.request().newBuilder().
                addHeader("Content-Type", "application/json").
                addHeader("Authorization","key=*my firebase key*").build()

                return chain.proceed(request)
            }
        }).addInterceptor(interceptor)

        val notificationRetrofit = Retrofit.Builder()
            .client(okHttpClientBuilder.build())
            .addConverterFactory(GsonConverterFactory.create())
            .baseUrl(FCM_URL)
            .build()
        notificationRetrofit.create(ServiceApi::class.java)
    }

ServiceApi

@POST("send/")
fun postNotification(@Body notificationBody: RequestBody) : Call<ResponseBody>

The log Http

2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: --> POST 
        https://fcm.googleapis.com/fcm/send/
2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: Content- 
Length: 117
    2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: Content-Type: application/json
    2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: Authorization: key=my firebase key
    2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: {"data":{"imageUrl":"https://i.imgur.com/KA1jrU7.jpg","textBody":"my content","title":"my title"},"to":"/topics/all"}
    2020-09-06 00:12:27.991 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: --> END POST (117-byte body)
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: <-- 404 https://fcm.googleapis.com/fcm/send/ (1206ms)
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: content-type: text/plain; charset=utf-8
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: x-content-type-options: nosniff
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: x-frame-options: SAMEORIGIN
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: x-xss-protection: 0
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: date: Sat, 05 Sep 2020 21:12:29 GMT
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: content-length: 135
    2020-09-06 00:12:29.198 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: alt-svc: h3-29=":443"; ma=2592000,h3-27=":443"; ma=2592000,h3-T051=":443"; ma=2592000,h3-T050=":443"; ma=2592000,h3-Q050=":443"; ma=2592000,h3-Q046=":443"; ma=2592000,h3-Q043=":443"; ma=2592000,quic=":443"; ma=2592000; v="46,43"
    2020-09-06 00:12:29.199 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: A valid push subscription endpoint should be specified in the URL as such: https://fcm.googleapis.com/wp/dHIoDxE7Hdg:APA91bH1Zj0kNa...
    2020-09-06 00:12:29.199 32059-32244/com.bagi.soreknetmanager I/okhttp.OkHttpClient: <-- END HTTP (135-byte body)
    2020-09-06 00:12:29.201 32059-32059/com.bagi.soreknetmanager D/MainActivity: Response{protocol=h2, code=404, message=, url=https://fcm.googleapis.com/fcm/send/}

The implementation that works great without using Retrofit

 val notificationBody = NotificationBody(notificationData, "/topics/all")
    val jsonPayload = createJsonFromObject(notificationBody)
     val thread = Thread(Runnable {
    try {
        val interceptor = HttpLoggingInterceptor()
        interceptor.level = HttpLoggingInterceptor.Level.BODY
        var client = OkHttpClient().newBuilder().addInterceptor(interceptor)
            .build()
        var mediaType = "application/json".toMediaTypeOrNull()
        var body: RequestBody = RequestBody.create(
            mediaType,
            jsonPayload
        )
        var request: Request = Request.Builder()
            .url("https://fcm.googleapis.com/fcm/send")
            .method("POST", body)
            .addHeader("Content-Type", "application/json")
            .addHeader(
                "Authorization",
                "key=my firebase key"
            )
            .build()
        var response: okhttp3.Response = client.newCall(request).execute()
    } catch (e: Exception) {
        e.printStackTrace()
    }
})

thread.start()

Answer 1

Error is in your URL.. Check your FCM_URL, it is incomplete, you forgot to append "send" word

FCM_URL = "https://fcm.googleapis.com/fcm/"

Correct URL-

FCM_URL ="https://fcm.googleapis.com/fcm/send"