Retrofit Basic Authentication in Android

Upasana | December 30, 2019 | 2 min read | 3,730 views

We will add basic authentication in android app using retrofit and okhttp using Okhttp authentication interceptor mechanism.

Retrofit (v2.7.0) and OkHttp (v4.2.2) are open source rest-client libraries for Android. You can use these libraries in your project to easily consume REST APIs.

Approach

You will have to create a Request interceptor (BasicAuthInterceptor) which extends Interceptor class of OkHttp library. Then, override intercept function and add your credentials into the request. Generate basic credentials with Credentials class of package OkHttp by using its basic function. Pass username and password to basic function as function arguments and it will return base64 encoded string. Use this string with Authorization header.

Gradle setup

Add Retrofit and OkHttp dependencies in your build.gradle file.

/app/build.gradle

    //Retrofit Libraries
    implementation 'com.squareup.retrofit2:retrofit:2.7.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.7.0'
    //OkHttp Libraries
    implementation 'com.squareup.okhttp3:okhttp:4.2.2'
    implementation 'com.squareup.okhttp3:logging-interceptor:4.2.2'

Interceptor for Basic Auth

OkHttp Interceptors are a powerful mechanism that can monitor, rewrite, and retry calls. We will develop an interceptor that will inject Basic Auth headers to each outgoing request.

BasicAuthInterceptor.kt

class BasicAuthInterceptor(username: String, password: String): Interceptor {
    private var credentials: String = Credentials.basic(username, password)

    override fun intercept(chain: Interceptor.Chain): okhttp3.Response {
        var request = chain.request()
        request = request.newBuilder().header("Authorization", credentials).build()

        return chain.proceed(request)
    }
}

We Are almost done, Now we just need to add this interceptor in your OkHttp Client and then add OkHttp Client in your retrofit instance.

Inject interceptor into OkHttpClient

val client =  OkHttpClient.Builder()
    .addInterceptor(BasicAuthInterceptor(Username, Password))
    .build()

val retrofit = Retrofit.Builder()
    .baseUrl("https://api.example.com")
    .client(client)
    .build()

Complete Solution

class BasicAuthInterceptor(username: String, password: String): Interceptor {
    private var credentials: String = Credentials.basic(username, password)

    override fun intercept(chain: Interceptor.Chain): okhttp3.Response {
        var request = chain.request()
        request = request.newBuilder().header("Authorization", credentials).build()

        return chain.proceed(request)
    }
}

class BasicAuthClient<T> {
    private val client =  OkHttpClient.Builder()
            .addInterceptor(BasicAuthInterceptor("<username>", "<password>"))
            .build()

    val gson = GsonBuilder()
            .setLenient()
            .create();

    private val retrofit = Retrofit.Builder()
            .baseUrl("https://api.example.com")
            .client(client)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .build()

    fun create(service: Class<T>): T {
        return retrofit.create(service)
    }
}

interface DemoRemoteService {

    @GET("/profile")
    fun getProfile(): Call<Profile>
}

class Demo {
    fun loadProfile() {
        val call = BasicAuthClient<DemoRemoteService>().create(DemoRemoteService::class.java).getProfile()

        call.enqueue(object: Callback<Profile> {
            override fun onFailure(call: Call<Profile>, t: Throwable) {
                Log.e("DemoClass", t.message, t)
            }

            override fun onResponse(call: Call<Profile>, response: Response<Profile>) {
                if (response.isSuccessful) {
                    Log.i("DemoClass", "Profile Loaded.")
                } else {
                    Log.e("DemoClass", "Error: ${response.code()} ${response.message()}")
                }
            }
        })
    }
}