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When choosing between these two popular web API (application programming interface) formats it can be surprisingly difficult to know which one you should select for your infrastructure.

Although both Rest (Representational State Transfer) and SOAP(Simple Object Access Protocol) share attributes in common with how they handle HTTP protocols, there are a number of key differences as discussed in this article.


Introduction to SOAP

SOAP is an acronym for Simple Object Access Protocol, but most importantly it is first and foremost a standardised messaging protocol. Web APIs leveraging SOAP are typically older, have larger message sizes, and are more rigid. Messages can only be represented using the XML format as opposed to RESTful APIs that typically use JSON. SOAP can therefore benefit from all the extensibility features offered by XML, such as XML namespaces and well-defined structural semantics. This makes SOAP a good choice for interoperability between systems as data transfer requirements (often referred to as contracts) can be strictly enforced if needed.

Our first specialist, Vadim Belsky, Head of Web Development at ScienceSoft, gives us his thoughts on the topics of these two API protocols:

“SOAP APIs are a go-to option when there's a need for increased WS-Security and transactional reliability (ACID - Atomicity, Consistency, Isolation, Durability).”

“At the same time, SOAP APIs are language, platform, and transport independent, and support both stateful and stateless operations. This makes them widely applicable in integrations with legacy applications.”

Introduction to REST

Vadim continues:

“REST (REpresentational State Transfer) is an architecture style for distributed systems. A RESTful API is an API built with all the requirements and constraints of the architectural style in mind.”

REST APIs are the modern and preferred design choice used for APIs exposed to the web, as opposed to the older SOAP-based APIs. RESTful API design uses the existing HTTP protocol to represent different requests based on what HTTP method is used. For example, a GET request represents the fetching of data whereas a POST request represents data being sent from the client to the server, which is usually persisted in a data-store.

By leveraging the HTTP protocol, the server and client can remain completely decoupled from each other. As long as the server maintains its promise to respond to requests as defined by its RESTful API, the server is free to update its technology stack or internal implementation details, such as server-side caching and API version control. This flexibility provides great scalability potential - one of the major advantages of RESTful APIs.

Vadim also added;

“RESTful APIs are also more flexible, faster (since no extensive data processing is required), and support multiple data formats as plain text, HTML, XML, and JSON.”

Key Features & Benefits of Soap & Rest

We have gathered insights on the following benefits and notable differences between SOAP vs Rest from experienced software engineers and developers in order to help you decide which tool is right for you.

Our next expert Marie Starck, freelance full-stack software developer, details the main advantages users will notice when testing out both REST and SOAP against each other;

Advantages of using REST:

  • Rest is made for the web and as a result is compatible with different message formats, with JSON being the one most commonly used.
  • It's lightweight, easy to parse and works wonderfully well with common web languages such as JavaScript.
  • Faster, uses less bandwidth and it can be cached. This feature is particularly helpful for websites who want to offer offline-first capabilities.
  • Small learning curve. Thanks to its simplicity, REST is often the first (and sometimes only API) taught in universities and bootcamps.

Benefits of using SOAP:

  • Freedom in terms of the transport used, with SOAP a request can be sent over HTTP, SMTP, TCP and others. (REST is limited to HTTP).
  • Tighter security, as SOAP standardizes how messages are secured with WS-Security.
  • SOAP is also supplied with ACID compliance, further enhancing security.
  • In case of failure, SOAP can retry the request using it’s built-in retry logic (contrary to Rest which leaves it up to the client to retry or not).

Rest VS Soap: Which Should You Choose?

“In the matter of REST vs SOAP, they are hard to compare and contrast because they are objectively different things.”

says Yoseph Redding of DevOps and API consulting firm Shuttl.

“REST is an architectural style defined in Roy Fielding's Dissertation, Architectural Styles and the Design of Network-based Software Architectures, while SOAP is a protocol that defines how we access operations on a network.”

“REST only really defines how an application's interface should be structured and built, but leaves very little by way of how data is transmitted and which protocols can be used. Because of this fluidity, it is easier to build simple rest APIs, especially when engineers chose to use JSON as their data format.”

“Additionally, it is easier to cache because it typically uses the same standards and methods as normal website development.”

“However, with large APIs and many developers and clients consuming that API, REST becomes a challenge to work with because of its fluidity. Keeping track of API schema's and contracts are a real challenge.”

“SOAP is a protocol that defines how an object is defined. It is Contract first so you define your application up front and implement the business logic layer. It forces you to use XML as the data format and every message must be part of an envelope.”

“The problems with SOAP are numerous and difficult to overcome, especially in the modern technology stack.”

“Things like poor javascript support and lack of multiplexed connections make SOAP fall apart with any HTTP load balancers & it doesn't adapt well to new HTTP2 standards. The world has moved by and large to REST making the support for SOAP even smaller.”

“SOAP is an old piece of technology that should be avoided in my opinion. REST is pervasive but far from perfect. We at Shuttl focus on the new API formats including REST, GraphQL, and gRPC.”

In addition to this Chris Love, Professional Web Development Specialist at Love2Dev and author and speaker also contributed the following insights;

“You could look at SOAP as an inspirational forerunner of REST. The two provide ways for disparate systems to communicate.”

“One of the benefits of REST is that it works with any data format and tends to have smaller data requirements and use less bandwidth.”

“In contrast to this, SOAP relies on the two parties to understand the object structure or interfaces to manage communications.”

“REST relies more on URL structure, HTTP Request verbs and headers to drive the interactions.”

“SOAP is more popular for system-to-system communication, where REST is more commonly used for a client server.”

We hope this article has helped you to understand which API is best suited for your development project.

If you enjoyed this post on the benefits of Rest vs Soap then why not check out our post on Microservices vs APIs.

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