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Authenticator in Retrofit Android

Mohit Rajput on November 27, 2019

There is a general use-case in any application that the authentication token expires, and you need to refresh the internally. After upgrading the t...

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Mohit Rajput • Nov 20 '22

Many folks requested me to write a good implementation of TokenAuthenticator class i.e. how to refresh token.
Soon I will publish a new article on how I refresh tokens in authenticator.

ashubuntu • Aug 29 '20

if requestParams potentially consists of username and password, how do you provide that on the fly especially when the primary functionality of the app is to log the user out to the login activity when token is expired. By the way, this technique surely informs about 401 code.

Mohit Rajput • Aug 30 '20

Ideally we should have a refreshToken() function instead of login again.
But if you want to login again, then you can display a modal to user to enter username and password then resume this functionality as per given in blog.

Adri • Nov 29 '19

nice article, i think i should use this in my next project 😁

Mohit Rajput • Nov 30 '19

Thanks Adri. Sure we should use this.

Arief Turbagus (TB) • May 20 '21

Can I use this solution for parallel request API?

Mohit Rajput • May 27 '21 • Edited

Ofcourse. Make sure you manage authenticate() method accordingly.
E.g. make getUpdatedToken() call synchronize

RICARDO MORALES • Aug 7 '20

Awesome, thank you very much!!!!!!!

i need this for my work.
You saved me.

Mohit Rajput • Oct 12 '20

Thanks @ricardo

ayoub anbara 🇲🇦 • Aug 31 '22

If refresh token is expired also, and request refresh token return 401, how to handle this case?

Mohit Rajput • Sep 2 '22 • Edited

Here is the complete code which I used in one project:

package one.projectname.sdk.network

import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking
import okhttp3.Authenticator
import okhttp3.Request
import okhttp3.Response
import okhttp3.Route

/**
 * Created by Mohit Rajput on 09/03/22.
 */
class TokenAuthenticator(
    private val tokenManager: TokenManager
) : Authenticator {
    override fun authenticate(route: Route?, response: Response): Request {
        synchronized(this) {
            val sessionData = if (isRefreshNeeded(response)) {
                runBlocking { getUpdatedSessionData() }
            } else {
                getExistingSessionData()
            }

            return response.request.newBuilder()
                .header(HeaderKeys.SESSION_ID, sessionData.sessionId)
                .header(HeaderKeys.REFRESH_ID, sessionData.refreshId)
                .build()
        }
    }

    private fun isRefreshNeeded(response: Response): Boolean {
        val oldSessionId = response.request.header(HeaderKeys.SESSION_ID)
        val oldRefreshId = response.request.header(HeaderKeys.REFRESH_ID)

        val updatedSessionId = tokenManager.getSessionId()
        val updatedRefreshId = tokenManager.getRefreshId()

        return (oldSessionId == updatedSessionId && oldRefreshId == updatedRefreshId)
    }

    private fun getExistingSessionData(): ApiResponse.SessionData {
        val updatedSessionId = tokenManager.getSessionId()
        val updatedRefreshId = tokenManager.getRefreshId()
        return ApiResponse.SessionData(
            sessionId = updatedSessionId,
            refreshId = updatedRefreshId
        )
    }

    private suspend fun getUpdatedSessionData(): ApiResponse.SessionData {
        val refreshTokenRequest =
            ApiResponse.RefreshSessionRequest(tokenManager.getRefreshId())
        return when (val result =
            getResult { userApiService().refreshSession(refreshTokenRequest) }) {
            is ApiResult.Success -> {
                val sessionData = result.data.data
                tokenManager.saveSessionId(sessionData.sessionId)
                tokenManager.saveRefreshId(sessionData.refreshId)
                delay(50)
                sessionData
            }
            is ApiResult.Error -> {
                MySdk.instance().mySdkListeners?.onSessionExpired()
                return ApiResponse.SessionData()
            }
        }
    }

    private class CustomNetworkStateChecker : NetworkStateChecker {
        override fun isNetworkAvailable() = true
    }

    private fun userApiService(): UserApiService {
        val retrofit = RetrofitHelper.provideRetrofit(
            RetrofitHelper.provideOkHttpClient(CustomNetworkStateChecker(), tokenManager)
        )
        return retrofit.create(UserApiService::class.java)
    }
}