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 | REST |
|---|---|
| SOAP is an XML-based messaging protocol | REST is not a protocol but an architectural style |
| SOAP has specifications for stateful implementation | REST follows only a stateless model |
| Minimal tooling/middleware is necessary. Only HTTP (mostly it’s HTTP based) support is required | URL typically references the resource being accessed/deleted/updated |
| A well-defined mechanism for describing the interface e.g. WSDL+XSD, WS-Policy | Formal description standards are not in widespread use. Everybody interprets on his own |
| The payload must comply with the SOAP schema | No constraints on the payload |
| Built-in error handling | No error handling though you can use HTTP error codes |
| Both SMTP and HTTP are valid application layer protocols used as Transport for SOAP | Tied to the HTTP transport model |
| SOAP web services totally ignore the web caching mechanism | RESTful web services take full advantage of web caching mechanisms because they are basically URL based |
| Hard to learn | Easy to learn because everybody understands HTTP |
| SOAP security is well standardized through WS-SECURITY | Security 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 useful | Other 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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