What are the differences between REST and SOAP API?

Summary: In this tutorial, you will learn with examples the differences between REST and SOAP API.

REST (Representational State Transfer) and SOAP (Simple Object Access Protocol) are both web service communication protocols. They allow different systems to communicate with each other over the internet.

What is REST API?

REST (Representational State Transfer) is an architectural style that defines a set of constraints and properties for creating web services.

It is based on the principles of representational state transfer and HTTP, and it is designed to be simple, flexible, and scalable.

REST APIs use HTTP methods (such as GET, POST, PUT, DELETE, etc.) to perform operations on resources, and they return responses in a format such as XML, JSON, or HTML.

Here is an example of a REST request and response:

REST Request:

GET /api/rest/prices/ABC HTTP/1.1
Host: example.com

REST Response:

HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: nnn

{
  "price": 19.95
}

What is SOAP API?

SOAP (Simple Object Access Protocol) is a protocol that defines a set of rules for exchanging messages in the form of XML documents over the internet.

It is designed to be extensible, neutral (able to operate over a variety of communication protocols), and independent (able to operate in a variety of environments).

SOAP APIs use HTTP or other protocols to transmit messages, and they can include additional information in the message header, such as authentication details or error-handling instructions.

Here is an example of a SOAP request and response:

SOAP Request:

POST /api/soap HTTP/1.1
Host: example.com
Content-Type: text/xml; charset=utf-8
Content-Length: nnn

<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
  <soap:Header>
    <m:transaction xmlns:m="http://www.example.com/transaction">abc123</m:transaction>
  </soap:Header>
  <soap:Body>
    <m:getPrice xmlns:m="http://www.example.com/prices">
      <m:item>ABC</m:item>
    </m:getPrice>
  </soap:Body>
</soap:Envelope>

SOAP Response:

HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: nnn

<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding">
  <soap:Body>
    <m:getPriceResponse xmlns:m="http://www.example.com/prices">
      <m:price>19.95</m:price>
    </m:getPriceResponse>
  </soap:Body>
</soap:Envelope>

Differences between REST and SOAP

Here are some key differences between REST and SOAP:

1. Structure: SOAP uses a predetermined structure for the message, which is an XML document. REST does not have a specific structure for the message, and it can be sent in various formats, such as XML, JSON, or HTML.
2. Methodology: SOAP is a protocol that follows a strict set of rules for communication. It specifies the structure of the message, the way to encode it, and the way to transmit it. REST is an architectural style that does not prescribe any specific rules for communication.
3. Performance: REST APIs are generally faster and simpler than SOAP APIs, because they use fewer resources and can be optimized for the specific needs of the client. SOAP APIs, on the other hand, tend to be slower and more complex due to the strict structure of the message and the need for additional processing on the server.

Which is better?

It is difficult to say which is “better” between REST and SOAP, as both protocols have their own strengths and weaknesses and are suitable for different use cases.

Here are some factors to consider when deciding which protocol to use:

• Compatibility: SOAP is a widely-supported protocol and is suitable for use with a variety of programming languages and environments. REST is also widely supported, but it may not be as well-suited for use with certain technologies or platforms.
• Complexity: REST APIs are generally simpler and easier to use than SOAP APIs, because they have a more flexible structure and can use simpler data formats such as JSON. SOAP APIs, on the other hand, have a strict structure and require more complex XML messages, which can make them more difficult to develop and consume.
• Performance: REST APIs are generally faster and more efficient than SOAP APIs, because they use fewer resources and can be optimized for specific needs.
• Security: Both REST and SOAP APIs can be secured using a variety of methods, such as authentication, encryption, and authorization. SOAP APIs may offer more robust security options due to the additional information that can be included in the message header, but REST APIs can also be secured using similar methods.

Ultimately, the choice between REST and SOAP will depend on the specific needs of your application and the requirements of the systems you are integrating with. It may be helpful to consider the compatibility, complexity, performance, and security requirements of your application when deciding which protocol to use.