What are REST API and SOAP? How do they differ?

REST API (Representational State Transfer) is an architectural style for creating web services that uses standard HTTP methods (GET, POST, PUT, DELETE) to interact with resources represented as URLs. REST focuses on simplicity, scalability, and the use of standard protocols.

SOAP (Simple Object Access Protocol) is a message exchange protocol based on XML that defines strict standards for message formatting, transmission, and processing. SOAP is often used in enterprise systems where formal specifications and advanced security features are important.

Main differences:

• Data format: REST typically uses JSON or XML, SOAP uses only XML.
• Protocol: REST uses HTTP directly, SOAP can operate over HTTP, SMTP, and others.
• Standards: SOAP has strict standards and specifications (WS-Security, WS-AtomicTransaction, etc.), REST is more flexible.
• Complexity: REST is simpler to implement and use, SOAP is more complex but powerful.

Example REST request:

GET /users/123 HTTP/1.1
Host: example.com

Example SOAP message:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ex="http://example.com/">
   <soapenv:Header/>
   <soapenv:Body>
      <ex:GetUser>
         <ex:UserId>123</ex:UserId>
      </ex:GetUser>
   </soapenv:Body>
</soapenv:Envelope>