Difference between SOAP and REST

Although SOAP (Simple Object Access Protocol)  and REST (Representational State Transfer)– both serve the same purpose i.e. building applications based on SOA (Service-Oriented Architecture), yet they are pretty much different in the way how they help in achieving the final output.

1. What is SOAP?

SOAP protocol was designed much earlier than REST. The main motive behind designing SOAP was to ensure that programs built on different platforms and programming languages could exchange data in an easy and agreed-upon manner.

SOAP sets a few rules that the service providers and service consumers must abide by for successful data transfer between them. It also provides inbuilt mechanisms for security using different schemes.

You can see an example of SOAP API in this linked post.

2. What is REST?

REST is a new alternative for developing enterprise-grade services/APIs, inspired by HTTP (GET, POST, PUT and DELETE). It defines 6 principles that are called REST constraints.

Any web service that follows the constraints of REST can be called a RestFul web service. Spring WebMVC modules provides specific capabilities to write REST APIs from scratch using the Spring framework.

3. Difference Between SOAP and REST

Let us note down the most noticeable differences between SOAP and REST-based APIs:

SOAP is an XML-based messaging protocolREST is not a protocol but an architectural style
SOAP has specifications for stateful implementationREST follows only a stateless model
Minimal tooling/middleware is necessary. Only HTTP (mostly it’s HTTP based) support is requiredURL typically references the resource being accessed/deleted/updated
A well-defined mechanism for describing the interface e.g. WSDL+XSD, WS-PolicyFormal description standards are not in widespread use. Everybody interprets on his own
The payload must comply with the SOAP schemaNo constraints on the payload
Built-in error handlingNo error handling though you can use HTTP error codes
Both SMTP and HTTP are valid application layer protocols used as Transport for SOAPTied to the HTTP transport model
SOAP web services totally ignore the web caching mechanismRESTful web services take full advantage of web caching mechanisms because they are basically URL based
Hard to learnEasy to learn because everybody understands HTTP
SOAP security is well standardized through WS-SECURITYSecurity is provided on the HTTP protocol layer such as basic authentication and communication encryption through TLS
When you are publishing an API to the outside world that is either complex or likely to change, SOAP will be more usefulOther than that, REST is usually the better option

Feel free to add more differences if you know them. It will help others as well.

Happy Learning !!


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