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  • Writer's pictureShannon

APIs Aren't Just For Devs Pt. 8 - SOAP vs. REST

As I keep thinking through the vast amount of content here, it makes sense to talk about SOAP APIs vs. REST APIs. What does this mean for the post? I'm probably still a few posts away from the end of this series. I hope you're enjoying the series!

As a reminder, if you're starting here, there are more posts to the series. Take a peek at the full list of posts that I've created thus far:

REST APIs are used almost unanimously. SOAP APIs aren't used as frequently. I can fondly remember my first SOAP errors supporting a VMware cluster. I think I said "SOAP errors? What are those?"

The good news is you don't have to approach a similar situation with the clueless nature I had at the time. So what is a SOAP API?

A SOAP API (Simple Object Access Protocol API) is a type of web service that allows different software systems to communicate and exchange data over the internet (just like REST, but different). SOAP is a protocol for exchanging structured information in the implementation of web services. It uses XML (Extensible Markup Language) as its message format for transmitting data between client and server applications (and only XML).

Here's a quick overview of the key components and characteristics of a SOAP API:

  1. Protocol: SOAP is a protocol that defines a set of rules for structuring messages and performing remote procedure calls (RPCs) between applications.

  2. Message Format: SOAP messages are usually encoded in XML, making them platform and language independent. The XML structure consists of an envelope that contains a header and a body. The header can include optional information such as authentication details, while the body carries the actual data being exchanged.

  3. Transport: SOAP can work over different transport protocols, such as HTTP, SMTP, TCP, or JMS (Java Message Service). However, it is most commonly used over HTTP or HTTPS, making it suitable for communication over the web.

  4. WSDL (Web Services Description Language): To use a SOAP API, developers typically rely on a WSDL document that provides a standardized description of the API's interface. The WSDL file specifies the methods, data types, and endpoints available for communication with the service.

  5. Protocol Independence: One of the key advantages of SOAP is that it allows for protocol independence. This means that SOAP messages can be transported over various lower-level protocols, depending on the requirements of the application.

  6. Standardized: SOAP is based on industry standards and is well-suited for enterprise-level applications and integration scenarios. It supports ACID transactions, which ensures data consistency in distributed systems.

  7. Stateful or Stateless: SOAP APIs can be designed to be either stateful or stateless. Stateful APIs maintain the session state between requests, while stateless APIs treat each request independently without any context retention.

However, despite its robustness and flexibility, SOAP became less popular compared to REST APIs. REST APIs tend to use simpler data formats like JSON and are easier to work with for many developers. Nonetheless, SOAP is still used in specific enterprise environments where its features are advantageous, especially in situations where strict security, reliability, and transactional support are required.

So now you know what SOAP APIs are! Huzzah!

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