Handle exceptions thrown by a custom okhttp Interceptor in Kotlin Coroutines

You should subclass IOException and use that to send information from your interceptors to your calling code.

We consider other exceptions like IllegalStateException to be application crashes and do not send them over thread boundaries because we don’t want to burden most callers with catching them.

You may catch the exception in your custom Interceptor and return an empty response with some specific message and code. I have implemented a custom Interceptor to handle the situation like when you do not have or slow internet connection etc... Actually coroutine's suspend functions throws exception when dealing with network calls. In my experience, you can follow 2 approaches. 1. wrap your all network call in try...catch or 2. create a custom Interceptor and handle exceptions there and return some specific response.

Approach 1:

try {    webservice.login(username, password)} catch (e: Exception) {    //...}

Approach 2:

Create a custom Interceptor and handle exception there.

class LoggingInterceptor : Interceptor {   @Throws(Exception::class)   override fun intercept(chain: Interceptor.Chain): Response {      val request = chain.request()      try {          val response = chain.proceed(request)                  val bodyString = response.body()!!.string()          return response.newBuilder()            .body(ResponseBody.create(response.body()?.contentType(), bodyString))            .build()      } catch (e: Exception) {          e.printStackTrace()          var msg = ""          when (e) {             is SocketTimeoutException -> {                msg = "Timeout - Please check your internet connection"             }             is UnknownHostException -> {                msg = "Unable to make a connection. Please check your internet"             }             is ConnectionShutdownException -> {                msg = "Connection shutdown. Please check your internet"             }             is IOException -> {                msg = "Server is unreachable, please try again later."             }             is IllegalStateException -> {                msg = "${e.message}"             }             else -> {                msg = "${e.message}"             }          }          return Response.Builder()                .request(request)                .protocol(Protocol.HTTP_1_1)                .code(999)                .message(msg)                .body(ResponseBody.create(null, "{${e}}")).build()      }   }}

I have created gist for complete implementation of LoggingInterceptor with print logs of request and response. LoggingInterceptor

I dont know what exactly you need, but understood like this:

    OkHttpClient okHttpClient = new OkHttpClient.Builder()          .addInterceptor(new Interceptor() {            @Override            public okhttp3.Response intercept(Chain chain) throws IOException {                Request request = chain.request();                okhttp3.Response response = chain.proceed(request);                // todo deal with the issues the way you need to                if (response.code() == SomeCode) {                   //do something                    return response;                }                return response;            }        })        .build();Retrofit.Builder builder = new Retrofit.Builder()          .baseUrl(url)        .client(okHttpClient)        .addConverterFactory(GsonConverterFactory.create());Retrofit retrofit = builder.build();