REST vs SOAP: The Key Features and Differences

The concept of a “web service” can mean different things to different people. In its most basic form, a web service is simply a way to access and interact with the Internet for online users and customers.

But, for web developers, it often means establishing communication between various devices and software. Web engineers must decode the underlying processes and make it easy for general users to use web services directly. But how do they enable this web communication?

There are two primary traditional ways to do this: using SOAP or REST standards. These two API design styles have their significance but have become a topic of debate due to their different uses.

Below, we’ll discuss SOAP API and REST API in detail, highlighting their key similarities and differences.

The Meaning of “API”

First off, what is an API? In simple terms, an API or Application Programming Interface is a communication medium between two applications. It helps them exchange information and facilitates a seamless transfer of requests and responses.

Therefore, an API is a piece of software code that allows data transmission under a set of standards between two software products. It has two primary parts:

  • The technical specification: An API has data delivery protocols and exchange options written in the form of an API request.
  • The software interface: An API adheres to the given specification and is the messenger between two applications.

Let’s explore one common API use case. Many eCommerce platforms and eCommerce software are leveraging APIs to facilitate seamless integration. For example, when software vendors need online store data for their solution to perform its core functionality, they integrate it with eCommerce platforms’ APIs. This integration results in streamlining operations for eCommerce retailers.

These APIs (or the applications) use two major protocols or standards to communicate, SOAP and REST. Let’s check them out in detail.

SOAP API: Meaning and Examples

SOAP or Simple Object Access Protocol is a standard set of rules that define how API requests and responses are exchanged between two applications. It uses XML (Extended Markup Language) format for its envelope, header, and body elements of the text enclosed in request and response messages. SOAP uses WSDL (Web Services Description Language) to define these messages’ schemas. For data transmission, SOAP uses the HTTP protocol.

SOAP’s API requests and responses are very structured, making it easy to use the web service. One example of a SOAP API is Magento’s SOAP API. The Magento SOAP API is a similar set of rules that define the format of API responses. It has three parts:

  • Envelope: Message and processing instructions
  • Encoding rules: Rules that define what types of data types will be used
  • Convention: Procedure calls and responses

The SOAP API provides different types of calls to Magento API to allow developers to work with data related to products, categories, and other elements.

REST API: Meaning and Examples

REST or Representational State Transfer is an architectural style that defines a set of rules for accessing and manipulating web resources over HTTP protocol. REST APIs have to follow six constraints of the REST style to interact with web resources. These constraints are:

  • Uniform Interface
  • Stateless
  • Cacheability
  • Client-Server
  • Layered System
  • Code on Demand

The REST APIs following these constraints typically adopt the following HTTP methods:

  • GET: To retrieve a web resource (can be an object, file, or block)
  • PUT: To update a resource or change its state
  • POST: To create a resource
  • DELETE: To delete a resource

One example of a REST API is the unified API by API2Cart. This unified API allows eCommerce software vendors and developers to connect their solutions with more than 40 eCommerce platforms at once. It has a user-friendly interface, transparent data interaction, clearly programmed methods, and access to all necessary data that allows the API to exchange data seamlessly.

Difference Between REST and SOAP APIs

Although both SOAP and REST APIs have their use cases, developers tend to prefer REST over SOAP. This is primarily because the REST style is less complex and less strict.

Let’s check out the difference between REST API and SOAP API in detail:

  1. REST is an architectural style and has no official standard to follow. It has six architectural constraints, though. SOAP is a protocol and hence, follows an official standard for data transfer.
  2. REST allows multiple standards like XML, JSON, HTTP, and URL. SOAP is limited to using XML and HTTP.
  3. REST exposes business logic in the form of URLs. SOAP does so with the help of service interfaces.
  4. SOAP uses Web Services Description Language to describe a web service’s functionality. REST’s equivalent is the Web Application Description Language. OpenAPI Specification is also popular to describe REST APIs.
  5. REST-style APIs can use SOAP protocol. SOAP protocol cannot use the REST style.
  6. REST can be implemented more easily and requires less bandwidth. SOAP’s implementation is complex and hence requires more bandwidth, especially pertaining to larger XML files.
  7. REST lacks compliance with ACID transactions that some data-heavy applications require. SOAP has compliance with ACID transactions and therefore has the upper hand over REST in this concern.
  8. REST APIs typically use SSL and HTTPS for security. SOAP uses SSL and WS-Security, allowing banking applications to prefer SOAP over REST.
  9. REST is a lightweight architectural style. SOAP is heavier than REST.
  10. REST uses JAX-RS as its Java API. SOAP uses JAX-WS.
  11. REST has to inherit security from the transport it is using. SOAP creates its own security.

Common Features of REST and SOAP APIs

REST and SOAP APIs share some similarities. They are as follows:

  • The connection between applications and the API (for both REST and SOAP) is via machine and human-readable server-side data.
  • Both REST and SOAP APIs primarily use HTTP protocols. However, they also use other protocols like SMTP (Simple Mail Transfer Protocol).
  • REST and SOAP APIs are compatible with XML documentation and can be used in request and response messages.
  • Both SOAP and REST web services are stateless. SOAP APIs can be made stateful, though, if needed.
  • The communication can be encrypted by HTTP and SSL in REST and SOAP APIs.
  • Both the APIs are convenient with JavaScript.

Conclusion

The comparison between REST and SOAP APIs provides a clear indication of the fact that REST is more preferred than SOAP. Still, there are some instances where SOAP API is needed. Besides, there are cases where web services are made from a combination of REST and SOAP APIs. So, it depends upon the use case to decide which API style will work best.