How to prevent Retrofit from clearing my cookies

In using Retrofit for network requests, it is crucial to ensure cookies are not cleared, particularly when handling user authentication and session management. Retrofit is a type-safe HTTP client, but it does not directly manage cookies. Typically, it relies on the underlying OkHttp client to handle HTTP communication, including cookie management. To prevent cookies from being cleared, you can adopt the following methods:

1. Use a Persistent CookieJar

To manage cookies, OkHttp allows customization of cookie storage through the CookieJar interface. Implement a persistent CookieJar to store cookies in persistent storage (such as SharedPreferences or a database). This ensures cookies remain intact even if the app is closed or the device is restarted.

Example code:

java
public class PersistentCookieJar implements CookieJar {
    private Context context;

    public PersistentCookieJar(Context context) {
        this.context = context;
    }

    @Override
    public void saveFromResponse(HttpUrl url, List<Cookie> cookies) {
        // Save cookies to SharedPreferences or a database
    }

    @Override
    public List<Cookie> loadForRequest(HttpUrl url) {
        // Load cookies from SharedPreferences or a database
        return cookies;
    }
}

OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .cookieJar(new PersistentCookieJar(context))
    .build();

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://example.com")
    .client(okHttpClient)
    .build();

2. Configure OkHttpClient

Ensure OkHttpClient is configured correctly and avoid creating a new instance for each request. Using a new OkHttpClient instance per request will cause previous cookie information to be lost.

Correct approach:

java
// Create a global singleton OkHttpClient
public class MyApplication extends Application {
    private static OkHttpClient okHttpClient;

    public static OkHttpClient getHttpClient() {
        if (okHttpClient == null) {
            okHttpClient = new OkHttpClient.Builder()
                .cookieJar(new PersistentCookieJar(context))
                .build();
        }
        return okHttpClient;
    }
}

// Use this singleton in Retrofit configuration
Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://example.com")
    .client(MyApplication.getHttpClient())
    .build();

3. Ensure Correct Server-Side Cookie Policy

The cookie attributes set by the server impact cookie persistence. For instance, if the server specifies the Max-Age or Expires attribute for a cookie, it will expire after the designated time. Verify that server-side settings align with your application's requirements.

4. Testing and Verification

During development, frequently test whether cookie management meets expectations. Utilize unit tests and integration tests to confirm that cookie persistence and transmission are accurate.

By implementing these methods, you can effectively manage cookies in Retrofit, ensuring they are not accidentally cleared and maintaining user session states.