REST vs. SOAP are both means of sharing data via web service APIs (application programming interfaces). Both are in wide use and have functionality suited for particular purposes. CIOs report that the vast majority of the APIs their teams develop today are REST APIs. Although REST is used more often, SOAP is still a viable choice in the right situation. If you’ve ever wondered which one to use for your applications and web services, you’ve come to the right place. This article will explain what SOAP and REST are, their key differences and how to choose which one is right for you.
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What Is SOAP?
Microsoft developed SOAP (Simple Object Access Protocol) as a web communication client-server protocol in the 1990s, and it has since been adopted as a web standard. SOAP can operate via a number of common protocols, such as HTTP (Hypertext Transfer Protocol), SMTP (Simple Mail Transfer Protocol), TCP (Transmission Control Protocol), or UDP (User Datagram Protocol). One of the breakthroughs of SOAP when it first became available was its platform independence. XML (Extensible Markup Language) is used exclusively for sending SOAP message data, a format understood by all modern systems. SOAP follows a strict set of standards. Some developers see this as rather inflexible, while others appreciate that it is a well-documented, highly structured option.
What Is REST?
REST (Representational State Transfer) is currently the default choice for most service providers. Unlike SOAP, it is an architectural style for software development. As SOAP is a protocol and REST is an architecture, comparing them can seem complicated and confusing. The important thing to remember is that, despite their differences, they are both popular ways of transferring data via APIs. While REST has certain constraints, it also allows for using various languages other than XML. This flexibility simplifies the process of using REST. For example, REST can typically perform requests with a simple URL instead of creating requests with XML. Although XML can be used with RESTful APIs, it’s more common to see JSON used for most public REST APIs. REST requires the use of HTTP or HTTPS (Hypertext Transfer Protocol Secure). It restricts itself to stateless operations, meaning that any web service classified as RESTful does not store the client state on the server.
Pros & Cons: SOAP vs. REST
So how do you know when to use REST or SOAP? There are various pros and cons to each that can help you decide.
SOAP Pros
SOAP is both simple and strict. Rather than seeing this as a bad thing, developers who use SOAP appreciate working within its well-documented framework. The strict regulations lead to increased accuracy in transmitting messages. Collaboration between two systems or organizations is improved because the rules for communication are narrow and set in place. The security around SOAP APIs is one of its strongest points. SOAP requests have WS Security (Web Services Security) built into the protocol. WS Security provides a layer of security beyond standard mechanisms. HTTPS, for example, only secures messages during transport between a client and server. WS Security secures messages beyond the transport layer and through the entire transaction. When a web service endpoint receives a SOAP message, it verifies security information in the message header to verify there has been no tampering with message contents. There are other WS extensions that add functionality to SOAP, too, like WSDL (Web Services Description Language). In a highly regulated scenario, like when transferring data to government organizations, SOAP and WS Security are often seen as the most secure option for transferring a message payload. A host of other WS extensions add optional and well-documented features. Other SOAP advantages include its support for stateful operations and its ability to use protocols other than HTTP or HTTPS.
REST Pros
Despite all these significant advantages, REST is far and away the most popular choice today. Why is this? The answer is that there are some things REST can do that SOAP cannot. First and foremost, RESTful APIs can make requests via a simple URL. SOAP always sends plain text XML messages, and encoding into the XML format can become tedious, especially with larger data sets. REST works well with JSON, a much more modern and efficient way to work with data. Nearly all programming languages and scripting languages in use today support the easy import and export of JSON data. On the off-chance JSON doesn’t work for your application, REST supports other data formats. As a lightweight architecture, REST vs. SOAP typically requires less bandwidth. REST is also highly scalable and can keep up with applications and data sets that grow over time. All these advantages have led to RESTful web services being adopted by tech giants and businesses of all sizes.
SOAP Cons
In comparison to REST, SOAP can seem like a less flexible option. Its long list of regulations and standards can make it complex to work with, especially for large-scale operations. The fact that SOAP only uses XML can be a big drawback, especially considering that some application frameworks have dropped support for the format in recent years. Compared to REST, SOAP is decidedly not lightweight. These factors, along with the fact that so many companies have adopted REST, have caused SOAP to fall into the background somewhat. Nonetheless, there are still instances where SOAP can be handy, as you will see later in this article.
REST Cons
If REST vs. SOAP can be said to have any downside, it’s that its greater flexibility introduces the possibility of more errors. Also, REST is stateless, so if you need a stateful connection, you have to choose SOAP. Although RESTful APIs can be secured, the WS standards provide a built-in layer of security that REST doesn’t have. REST APIs don’t have the built-in security mechanisms that SOAP has. REST APIs depend on HTTPS and security practices that ensure that only authorized users can access message data. Common ways to achieve this are with HTTP basic authentication, SSL, JSON web tokens, OAuth or OAuth 2, and API keys. REST is also limited to the HTTP protocol (or the more secure HTTPS). This is the same protocol the web uses to deliver HTML web pages. REST APIs should have detailed specifications to ensure security and reject requests that don’t match the declarations in their HTTP headers. This protects the underlying web application or service from malicious inputs, even if the client has gained access.
When SOAP Is the Right Choice
When should you use SOAP? There are two scenarios where SOAP is a clear choice over REST. Asynchronous operations: An asynchronous operation is very time-specific. It is when various signals or preceding events trigger new events rather than an external timer. REST limits itself to HTTP and HTTPS, neither of which are the ideal communication protocols for this purpose, as they may delay such an operation. SOAP supports additional communication protocols. Asynchronous operations are not suited for very simple or exceptionally complex tasks since it can be difficult to maintain correct timing. Stateful operations: Performing repetitive, chained tasks such as the financial industry requires means that you may need to retain certain client data within the server for future use. By default, REST is stateless. RESTful apps will not save any previous transactions, but SOAP supports stateful operations. There are many other such use cases for SOAP as well, but most have to do with some variation of these two operations.
When REST Is the Right Choice
While you can use REST to produce many, if not all, of the same results as SOAP with enough work from a professional developer, there are a few situations that REST is specially geared towards. Limited bandwidth, low-cost or simple operations: Why take the time to write complex XML when you can work from a simple URL to perform a basic, non-repetitive task? Additionally, if you have a lower-income business at the moment or limited bandwidth, REST will perform much faster and give better results in these situations than SOAP. Developing public APIs: REST is a helpful framework for developing public APIs because it is so common, and therefore it is easy to find other developers who understand it. Additionally, it is highly flexible, bringing lots of options to the marketplace. One example is Gmail, which is a RESTful API. GitHub features public APIs from various developers for various purposes, including health, jobs, cryptocurrency, machine learning, anti-malware, and even the weather, just to name a few. You can also use REST APIs to import or export content, create and manage credentials, and much more.
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