RESTful Services - WSDL Equivalent

I have been reading about REST and SOAP, and understand why implementing REST can be beneficial over using a SOAP protocol. However, I still don't understand why there isn't the "WSDL" equivalent in the REST world. I have seen posts saying there is "no need" for the WSDL or that it would be redundant In the REST world, but I don't understand why. Isn't it always useful to programmatically bind to a definition and create proxy classes instead of manually coding? I don't mean to get into a philosophical debate, just looking for the reason there is no WSDL in REST, or why it is not needed. Thanks.

Solution 1:

The Web Application Description Language (WADL) is basically the equivalent to WSDL for RESTful services but there's been an ongoing controversy whether something like this is needed at all.

Joe Gregorio has written a nice article about that topic which is worth a read.

Solution 2:

WSDL describes service endpoints. REST clients should not be coupled to server endpoints (i.e. should not be aware of in URLs in advance). REST clients are coupled on the media-types that are transfered between the client and server.

It may make sense to auto generate classes on the client to wrap around the returned media-types. However, as soon as you start to create proxy classes around the service interactions you start to obscure the HTTP interactions and risk degenerating back towards a RPC model.

Solution 3:

RSDL aims to turn rest like a hypermedia, in other words, it has more information than a service descriptor like WSDL or WADL. For example, it has the information about navigation, like hypertext and hyperlinks.

For example, given a current resource, you have a set os links to another resources related.

However, i didn't find Rest Clients that supports this format or Rest Server Solutions with a feature to auto generate it.

I think there is a long way for a conclusion about it. See the HTML long story and W3C vs Browsers lol.

For more details about Rest like Hypermedia look it: http://en.wikipedia.org/wiki/HATEOAS

Note : Roy Fielding has been criticizing these tendencies in Rest Apis without the hypermidia approach: http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven

My Conclusion : Now a Days, WADL is more common that Rest and Integration Frameworks like Camel CXF already supports WADL ( generate and consume ), because it is similar to WSDL, therefore most easy to understand in this migration process ( SOAP to REST ).

Let's see the next chapters ;)

Solution 4:

Isn't it always useful to programmatically bind to a definition and create proxy classes instead of manually coding?

Agree wholeheartedly, this is why I use Swagger.io

Swagger is a powerful open source framework backed by a large ecosystem of tools that helps you design, build, document, and consume your RESTful APIs.

So basically I use Swagger to describe my models, endpoints, etc, and then I use other tools like swagger-codegen to generate the proxy classes instead of manually coding it.

See also: RAML