How do I access response headers while using RxJava2 and Retrofit2?

Accessing Response Headers with RxJava2 and Retrofit2

This article will guide you through the process of accessing response headers while using RxJava2 and Retrofit2 in your Android or Java applications.

Understanding the Need

Retrieving response headers is crucial for various purposes:

• Authentication and Authorization: Headers can contain authentication tokens, allowing access to protected resources.
• Caching: Headers like “Cache-Control” provide information about data freshness and caching strategies.
• Content Information: Headers can reveal content type, encoding, and other essential details about the response.

Retrofit2 Call Adapters

Retrofit2 uses Call Adapters to convert the raw response into a suitable object. RxJava2 Call Adapter handles this conversion into Observables.

Methods for Accessing Response Headers

1. Using Call Adapter

Retrofit’s Call Adapter provides a straightforward way to obtain headers. This method relies on the “Call” object provided by Retrofit.

Example:

import retrofit2.Call;
import retrofit2.Response;

Call call = apiService.getData();

call.enqueue(new Callback() {
@Override
public void onResponse(Call call, Response response) {
if (response.isSuccessful()) {
// Access Headers
Map> headers = response.headers().toMultimap();
String contentType = response.headers().get("Content-Type");
// Process the response body
ResponseBody body = response.body();
} else {
// Handle errors
}
}

@Override
public void onFailure(Call call, Throwable t) {
// Handle network failures
}
});

2. Using RxJava2 Observables

When using RxJava2, you can observe the response and extract headers within the “onNext” method.

Example:

import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import retrofit2.Response;

apiService.getData()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer>() {
@Override
public void onSubscribe(Disposable d) {
// Handle subscription
}

@Override
public void onNext(Response response) {
if (response.isSuccessful()) {
// Access Headers
Map> headers = response.headers().toMultimap();
String contentType = response.headers().get("Content-Type");
// Process the response body
ResponseBody body = response.body();
} else {
// Handle errors
}
}

@Override
public void onError(Throwable e) {
// Handle errors
}

@Override
public void onComplete() {
// Indicate completion
}
});

Comparison

Conclusion

Accessing response headers with RxJava2 and Retrofit2 is a common requirement. This article has presented two effective methods, enabling you to choose the approach best suited to your project’s needs.