SOAP - What's the point?

Question

I mean, really, what is the point of SOAP?

Web services have been around for a while, and for a while it seemed that the terms \'SOAP\' and \'Web service\' were largely

Answer 1

The way I see it, SOAP might be more "flexible", but as a result it's just way too complicated (you mentioned the WSDL, which is always a stumbling block to me personally).

I get REST. It's simple. The only downside I might see is that you are limiting yourself to those 4 basic actions against a single resource, which might not exactly fit the way you view your data.

Answer 2

If you don't need the features of the WS-* series of protocols; if you don't need self-describing services; if your service cannot be completely described as resources, as defined by the HTTP protocol; if you don't like having to author XML for every interaction with the service, and parse it afterwards; then you need SOAP.

Otherwise, sure, use REST.

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There's been some question about the value of a self-describing service. My imagination fails me when it comes to imagining how anyone could fail to understand this. That's on me. Still, I have to think that anyone who has ever used a service much more complicated than "Hello, world" would know why it is valuable to have someone else write the code that accepts parameters, creates the XML to send to the service, sends it, receives the response, then turns that back into objects.

Now, I suppose this might not be necessary when using a RESTful service; at least not with a RESTful service that does not process complex objects. Even with a relatively simple service like http://www.earthtools.org/webservices.htm (which I've used as an example of calling a RESTful service), one benefits from understanding the structure of the returned data. Even the above service provides an XML Schema - it unfortunately doesn't describe the entire response. Given that schema one still has to manually process the XML, or else use a tool to produce serializable classes from the schema.

All of this happens for you when the service is described in a WSDL, and you use a tool like "Add Service Reference" in Visual Studio, or the svcutil.exe program, or I-forget-what-the-command-is-in-Eclipse.

If you want examples, start with the EarthTools services, and go on to any other services with more complicated messaging.

BTW, another thing that requires self-description is description of the messaging patterns and protocols supported by the service. Perhaps that's not required when the only choices are HTTP verbs over HTTP or HTTPS. Life gets more complicated if you're using WS-Security and friends.

Answer 3

The point of WSDL was auto-discovery. The idea was that you wouldn't have to write client code, it would be auto-generated.

BTW. next step beyond WSDL are Semantic Web Services.

Answer 4

I think SOAP appeals to the Java and .net crowd who may be more familiar with the old CORBA and COM and less familiar with internet technologies.

REST also has one major drawback: there is very little guidance on how to actually implement such a system. You will find significant variations on how many of the public RESTful APIs have been designed. In fact many violate key aspects of REST (such as using GET for manipulation or POST for retrieval) and there are disagreements over fundamental usage (POST/GET vs POST/GET/PUT/DELETE).

Answer 5

SOAP is a lightweight XML based structured protocol specification to be used in the implementation of services . It is used for exchanging structured information in a decentralized, distributed environment. SOAP uses XML technologies for exchanging of information over any transport layer protocol. It is independent of any particular programming model and other implementation specific semantics. Learn More about XML SOAP Messaging Framework

XML-based messaging framework that is 1) Extensible : Simplicity remains one of SOAP's primary design goals. SOAP defines a communication framework that allows for features such as security, routing, and reliability to be added later as layered extensions

2) Inter operable : SOAP can be used over any transport protocol such as TCP, HTTP, SMTP. SOAP provides an explicit binding today for HTTP.

3) Independent : SOAP allows for any programming model and is not tied to Remote procedure call(RPC). SOAP defines a model for processing individual, one-way messages. SOAP also allows for any number of message exchange patterns (MEPs) .Learn more about SOAP