REST API Interview Questions | REST API in Java

Introduction to REST API

In today's evolving digital landscape, REST API has emerged as an important tool for developers looking to enhance the functionality and connectivity of their applications. Whether you are a seasoned developer or just stepping into the world of programming, understanding the in and out of REST API can take your projects to the next level.

How REST API Works

Understanding the Functionality

REST API, which stands for Representational State Transfer Application Programming Interface, is a set of rules and protocols that allow different software applications to communicate with each other.

Smooth data transfer between servers and clients is made possible by REST API through the use of HTTP methods like GET, POST, PUT, and DELETE. Developers may simply access and change resources over the web thanks to this standard technique.

➡ HTTPS Methods and their meaning:

HTTP Method	Meaning
GET	Read Data
POST	Insert Data
PUT or PATCH	Update Data or Insert if a new id
DELETE	Delete Data

Benefits of Implementing REST API

• Scalability: REST API is inherently scalable, allowing developers to expand and modify their applications without disrupting the existing functionality.

• Flexibility: With REST API, developers have the freedom to choose the most suitable programming languages and technologies for their projects.

• Security: By implementing secure authentication methods and encryption protocols, REST API ensures that sensitive data remains protected from unauthorized access.

• Efficiency: REST API streamlines the communication process between different software components, resulting in faster response times and improved performance.

Below is the complete video for REST API.

Common REST API Interview Questions with Answers

It's a good idea to update yourself with common REST API interview questions and understand the concepts as you get ready for your next job interview in the tech sector.

Here are some questions that often come during interviews:

1. What is REST API, and how does it differ from SOAP API?

• You can check out 4th answer for this question below.

2. Can you explain the various HTTP methods used in REST API?

• The GET, POST, and PUT standard methods are defined by the HTTP protocol.

3. How do you handle authentication and authorization in REST API?

• Use basic authentication with your email address and password, your email address and an API token, or an OAuth access token to authenticate API requests. 

4. Difference between SOAP and REST API's

SOAP	REST
An XML based message protocol.	An architectural style protocol.
Uses WSDL for communication between consumer and provider.	Uses XML or JSON to send and receive data.
Invokes service by calling RPC method.	Simply calls service by URL path.
Does not return human readable result.	Result is readable which is just plain XML or JSON.
Transfer is over HTTP. Also Uses other protocols such as SMTP, FTP, etc.	Transfer is over HTTP only.
JavaScript can call SOAP, but it is difficult to implement.	Easy to call from JavaScript.
Performance is not great compared to REST.	Performance is much great compared to SOAP.

5. What is OAuth 2.0?

• OAuth 2.0 is an industry standard protocol for authorization.

• OAuth 2.0 can be achieve in different ways i.e., with different grant types.

• Authorization code and client credentials are the most commonly used grant types for OAuth.

6. What are the benefits of using RESTful web services in software development?

• RESTful web services enable complete client-server separation. In order for each component to develop independently, they simplify and remove different server components.

7. Can you walk us through the process of designing and implementing a REST API from scratch?

• Determine Resources - Modeling Objects: Identify the central resources or objects for your API first.

• Establish Model URIs: Create user-friendly URLs for every resource.

• Figure out the Resource Representations: Choose a data format that works for your resources.

Note: The following actions must be taken in order to define the resources, models, and operations of a REST API:

1. Click File ➡ New ➡ REST API to launch the Create a REST API wizard.
2. Provide the REST API a name.
3. Choose Create a REST API, then enter your own definitions for operations and resources.
4. Click Finish to complete the REST API creation.

8. What protocol does REST follow?

a) HTTP

b) FTP

c) SFTP

d) FTPS

Answer: a

9. What is the difference between POST and PUT methods in REST API? 

a) POST is used for creating resources, while PUT is used for updating resources 

b) POST updates the entire resource, while PUT updates only specific fields of a resource 

c) POST requires authentication, while PUT does not 

d) POST is used for creating resources, while PUT updates only specific fields of a resource

Answer: a

10. What is the difference between SOAP and REST APIs?

a) SOAP APIs use XML for data exchange, while REST APIs use JSON.

b) SOAP APIs are stateless, while REST APIs are stateful.

c) SOAP APIs are more lightweight than REST APIs.

d) SOAP APIs are more widely used than REST APIs.

Answer: a

Conclusion

REST API can help your development projects achieve new heights and unlock new possibilities for your applications. If you use HTTP methods and follow the principles of RESTful architecture, you may establish perfectly connected software components. Remember that preparation is the key to succeeding your next tech interview. Continue to be curious, determined, and constant learners.

Bonus: Below is the image explaining what each status code indicate.

Note: Majority of questions mainly appear related to the topics on SOAP and REST API's, Authorization and HTTPS methods.

Abbreviations Used: - FTP - File Transfer Protocol, SMPT - Simple Mail Transfer Protocol, HTTP - Hyper Text Transfer Protocol, API - Application Programming Interface, RPC - Request Procedure Calls, JSON - JavaScript Object Notation.

FAQs

1. What is an example of a REST API?

2. What is REST vs REST API?

3. What REST API is used for?

4. What are the 4 types of REST API?