REST vs SOAP — A Few Perspectives

In this article, we look at the major differences between SOAP and REST. Oops...actually, comparing the two is a little like comparing apples to oranges, as SOAP is a protocol format based on XML, whereas REST is an architectural approach.

You Will Learn

• What is REST?
• What is SOAP?
• How are REST and SOAP different?

You may also be interested in:  The Beginner’s Guide to Test RESTful APIs and Web Services

REST API

This is the second article in a series of articles on REST APIs. The first article is called "Introduction to REST API — RESTful Web Services."

REST vs SOAP

REST and SOAP are not really comparable. REST is an architectural style. SOAP is a message exchange format.

Let's compare the popular implementations of REST and SOAP styles.

• RESTful Sample Implementation: JSON over HTTP
• SOAP Sample Implementation: XML over SOAP over HTTP

At a high level, SOAP is about restrictions on your message structures, while REST is an architectural approach focused on using HTTP Transport.

• SOAP is particular about the Data Exchange Format. With SOAP, this is always SOAP-XML, which is an XML with envelope, header, and body. Both the request and response should adhere to the SOAP structure.
• REST is very particular about using HTTP as the transport protocol. It intends to make the best use of the features provided by HTTP — Request methods, Request headers, Response, Response headers, etc.

Message Interchange Format

• With SOAP, you use SOAP XML format for Request and Response
• With REST, there is no such fixed format. You could exchange messages based on XML, JSON or any other convenient format. JSON is the most popular among the used formats.

Service Definitions

• SOAP makes use of Web Service Definition Language (WSDL).
• REST does not have a standard service definition language. Even though WADL was one of the first standards to be proposed, it is not very popular. Swagger or Open API is another popular approach.

Transport

• SOAP does not place any restrictions on the kind of transport protocol. You could either use Web (which is HTTP) or MQ.
• REST intends to make the best use of HTTP Transport Protocol

Ease of Implementation

RESTFful services are typically a lot easier to implement than SOAP-based web services.

• REST typically uses JSON, which is easier to parse and process. In addition to that, REST does not require you to have a service definition in place to provide a web service.
• However, with SOAP, you are needed to define your service using WSDL, and greater overhead is involved in the processing and parsing of the SOAP-XML messages.

Check out our video on this:

Summary

In this article, we broadly looked at the differences between REST and SOAP.

Further Reading

5 Courses to Learn RESTful Web Services With Java and Spring in 2019

10 API Testing Tips for Beginners (SOAP and REST)