Retrofit ETAG and Caching

Retrofit ETAG and Caching

Retrofit is a popular library for making network requests in Android. One of its features is the ability to use ETAGs and caching to optimize network traffic and improve performance.

What is ETAG?

ETAG stands for “Entity Tag”. It’s a unique identifier that’s generated for a resource on a server. It allows you to determine if the resource has been modified since the last time it was retrieved.

How does ETAG work with Retrofit?

When making a request, Retrofit sends the ETAG of the last retrieved resource (if available) in the “If-None-Match” header. If the server finds that the resource hasn’t been modified, it responds with a “304 Not Modified” status code and doesn’t send the resource data.

Caching with ETAGs

By using ETAGs, you can implement a caching mechanism that automatically checks if the resource is up-to-date before fetching it from the network.

Implementation

Here’s a basic implementation of ETAG caching with Retrofit:

Step 1: Add Retrofit Dependencies

implementation("com.squareup.retrofit2:retrofit:2.9.0")
implementation("com.squareup.retrofit2:converter-gson:2.9.0")

Step 2: Create a Cache Interceptor

import okhttp3.CacheControl
import okhttp3.Interceptor
import okhttp3.Request
import okhttp3.Response

class CacheInterceptor : Interceptor {

    override fun intercept(chain: Interceptor.Chain): Response {
        val request = chain.request()

        // Check if the request should be cached
        val cacheControl = CacheControl.Builder()
                .maxAge(5, TimeUnit.SECONDS)
                .maxStale(60, TimeUnit.SECONDS)
                .build()

        val cachedResponse = chain.proceed(request).cacheControl(cacheControl)

        return cachedResponse
    }
}

Step 3: Create a Retrofit Client

import okhttp3.OkHttpClient
import okhttp3.logging.HttpLoggingInterceptor
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

class ApiClient {

    companion object {
        fun getClient(): Retrofit {
            val logging = HttpLoggingInterceptor()
            logging.setLevel(HttpLoggingInterceptor.Level.BODY)

            val httpClient = OkHttpClient.Builder()
                .addInterceptor(CacheInterceptor())
                .addInterceptor(logging)
                .build()

            return Retrofit.Builder()
                .baseUrl("https://your-api-base-url.com/")
                .addConverterFactory(GsonConverterFactory.create())
                .client(httpClient)
                .build()
        }
    }
}

Step 4: Create an API Interface

import retrofit2.Call
import retrofit2.http.GET

interface ApiService {

    @GET("/data")
    fun getData(): Call // Replace with your actual data type
}

Step 5: Make a Network Request

val apiService = ApiClient.getClient().create(ApiService::class.java)
val call = apiService.getData()

call.enqueue(object : Callback {
    override fun onResponse(call: Call, response: Response) {
        // Handle successful response
    }

    override fun onFailure(call: Call, t: Throwable) {
        // Handle error
    }
})

Benefits of using ETAG and Caching

• Reduced network traffic
• Improved app performance
• Lower battery consumption
• Enhanced user experience

Comparison with Last-Modified Header

Conclusion

By incorporating ETAG and caching into your Retrofit applications, you can significantly improve network performance and enhance the overall user experience.