20 Retrofit Interview Questions and Answers

Retrofit is a type of rest client that allows Android and Java developers to turn HTTP API into a Java interface. In other words, it makes it easy for developers to access web services without having to write a lot of code. If you’re applying for a position that involves Android or Java development, it’s likely that you’ll be asked questions about Retrofit during your interview. In this article, we discuss the most common Retrofit questions and how you should answer them.

Retrofit Interview Questions and Answers

Here are 20 commonly asked Retrofit interview questions and answers to prepare you for your interview:

1. What is Retrofit?

Retrofit is a type of library that allows you to connect to a REST API in your Android app. It makes it easy to parse JSON data and to make network requests, and it also provides some nice features like caching and automatic retries.

2. How do you install Retrofit in Android?

You can install Retrofit using Gradle. First, add the following dependency to your build.gradle file:

compile ‘com.squareup.retrofit2:retrofit:2.1.0’

Then, add the following to your AndroidManifest.xml file:

Finally, add the following to your proguard-rules.pro file:

-keepattributes Signature
-keepattributes Exceptions
-keep class com.squareup.okhttp3.** { *; }
-keep interface com.squareup.okhttp3.** { *; }
-dontwarn com.squareup.okhttp3.**

3. Can you explain the architecture of Retrofit?

Retrofit is a type-safe HTTP client for Android and Java. It makes it easy to consume JSON or XML data from a web service. It is built on top of the OkHttp library. Retrofit uses annotations to define how to map an endpoint to a Java interface. It can also be used with RxJava to return observable objects.

4. What are the advantages and disadvantages of using Retrofit?

The main advantage of using Retrofit is that it makes it easy to connect to a REST API and retrieve data. The main disadvantage is that it can be difficult to set up, especially if you are not familiar with REST APIs.

5. What is the difference between a GET request and a POST request?

A GET request is a request for data from a server. A POST request is a request to create or update data on a server.

6. Can you give me an example of how to use @Path annotation with Retrofit?

The @Path annotation is used to specify a path parameter in the URL. For example, if you have a URL like http://example.com/users/{userId}, then you can use @Path(“userId”) to specify that the userId parameter should be replaced with the actual value.

7. What does the @QueryMap annotation do in Retrofit?

The @QueryMap annotation allows you to specify a map of query parameters for a request. This is useful for cases where you want to specify a large number of optional parameters for a request.

8. How can you pass query parameters when making an HTTP request using Retrofit?

When making an HTTP request using Retrofit, you can pass query parameters by annotating the request method with @Query. The query parameters will be appended to the URL.

9. What are some ways to handle error conditions when using Retrofit?

There are a couple of ways to handle error conditions when using Retrofit. One way is to use a custom ErrorHandler. This will give you the ability to handle errors in a way that makes sense for your application. Another way to handle errors is to use the @Retry annotation. This will cause Retrofit to automatically retry the request a specified number of times before giving up.

10. How can you add custom headers to your requests using Retrofit?

By default, Retrofit will add any headers specified in your @Headers annotation to every request. If you want to add headers only for a single request, you can use the @Headers annotation on that request.

11. How do you set up multiple endpoints for your API calls using Retrofit?

You can set up multiple endpoints for your API calls using Retrofit by creating a new instance of the Retrofit class for each endpoint. For example, if you have two endpoints, one for production and one for development, you would create two Retrofit instances, one for each endpoint. You would then create a new Service interface for each endpoint, and each Service would have its own methods for making API calls.

12. Is it possible to define multiple base URLs for your application? If yes, then how?

Yes, it is possible to define multiple base URLs for your application using Retrofit. This can be accomplished by using the @Url annotation on your Retrofit interface methods. This annotation takes a String value which represents the URL that you want to use for the specific method call.

13. Why do you think you might need to create custom converters?

There are a few reasons you might need to create custom converters. One reason is if you are working with a legacy API that doesn’t return data in a format that Retrofit can work with by default. Another reason is if you want more control over how the data is converted from its raw format into Java objects. Creating custom converters gives you the ability to fine-tune this process to better suit your needs.

14. What’s the best way to parse XML responses from a server with Retrofit?

The best way to parse XML responses from a server with Retrofit is to use a SimpleXmlConverter. This converter will take care of all of the heavy lifting for you and will allow you to focus on other aspects of your project.

15. How do you handle authentication when using Retrofit?

When using Retrofit for authentication, there are a few different approaches that can be taken. One approach is to use an interceptor, which can be used to add an authentication header to every request that is made. Another approach is to use a RequestInterceptor, which can be used to add an authentication header to specific requests. Finally, you can also use a Authenticator, which can be used to handle authentication errors.

16. Do you have any experience working with RxJava-based Reactive Programming using Retrofit?

Yes, I have experience working with RxJava-based Reactive Programming using Retrofit. I have used it to build Android applications that consume data from RESTful web services.

17. What would you recommend as the best practices for creating clean interfaces when using Retrofit?

I would recommend a few things when it comes to creating clean interfaces with Retrofit. First, make sure that your interface methods are well-named and clearly indicate what they are doing. Second, use annotations to clearly specify the HTTP method and endpoint for each interface method. Finally, use Retrofit’s built-in converter methods to deserialize your data into POJOs.

18. How do you handle asynchronous operations when using Retrofit?

When using Retrofit, you can use the @retrofit annotation to specify that a method is asynchronous. This annotation will cause the Retrofit library to automatically create a new thread for the method call and will return a Call object that can be used to track the status of the operation.

19. How do you get access to the response body when using Retrofit?

When you are using Retrofit, you can get access to the response body by using the @Body annotation. This annotation will take the response body and convert it into a Java object for you to use.

20. What is the role of Jackson Converter in Retrofit?

The Jackson Converter is responsible for converting Java objects into JSON format and vice versa. This is important because it allows Retrofit to interface with a variety of different backends.