Re: ByRef/Ref passing in Web Services
- From: Brock Allen <ballen@xxxxxxxxxxxxxxxxx>
- Date: Tue, 03 May 2005 06:30:24 -0700
Where is this in the SOAP spec -- and don't say Section 5 encoding rules, since that's long outdated. If it is in the modern version of the SOAP spec, then I'd be suprised (I can't be bothered to go look). If it's not, then I'd rephrase "WebServices can indeed pass ByRef/ref parameters" to say "The ..NET framework will map a ref param onto WebServices semantics". Just a subtle, yet important distinction.
So my question is - If I mark an int as "ref" in a WebMethod, it seems to work. But if I am exposing a dumb schema (non-intelligent business object), then it doesn't work. (Dumb Schema Non Intelligent Business object example - a class customer, with private string FirstName, encapsulated as a property - that's it !! (Default public constructor present))
I'm not sure what a "Dumb Schema" means, but my sense is that your approach to web services is from an object mindset which is fatal. My sense is that you also already know this, but at the sake of being redundant, I'll mention it again. Web Services are about XML message passing. Objects and [WebMethods] are simply a convenience afforided to you by the framework you choose to use to implement WebServices. That framework is very good at hiding the details of the underlying messaging framework (SOAP, WSDL, XSD, etc). And in fact it's too good at times. My point is that the framework is so good at hiding the real thing we're working with (XML) such that it lets you do dumb things that you really shouldn't be doing. Sure those dumb things work if you have ..NET on both sides, but they don't make sense in a true introp scenario. The reason is that XML Schema is how we represent the structure of the XML we're sending across the wire, and the [WebMethods] framework infers an XSD from your parameters' type definitions. But there are so many things you can do with classes in .NET that don't map correctly to XSD. This is part of the debate over contract first.
Why should this work for only Intrinsic data types? :-/ .. or is there a trick to making it work with serialized object graphs?
So, this is a flawed way to think about web services. They're not objects, the'yre XML messages.
Now, of course, the point of the framework is to make it easier to develop web services, so you can pass objects as long as you know that the inferred XSD is correct. [And finally, the answer I know you're looking for] The .NET WebService framework uses the XmlSerializer to do this mapping (for the actual object instances passed back and forth, at least). XmlSerializer is a XSD friendly object serilization/deserilization implementation. One part of that is that it only will access what's public because the private keyword is a sementic specific to a .NET class (and web services aren't about passing classes/objects). This is in contrast to the .NET remoting serilization implementation (SoapFormatter, and BinaryFormatter). The purpose of those is to faithfully pass objects across the network because we have .NET on both sides. This will dig into private fields to correctly serialize all of the state so that the object can be fully (and correctly) deserialized on the other side.
In my web service implementations I never take .NET classes meant to be used by other .NET code and pass those pas paremeters or return values from my webservice. I instead create "shell" classes that only hold public fields and perhaps references to other "shell" classes. I create them in such a way that I know they'll be serialized out correctly according to the XSD rules. This way I'm able to utilize the .NET framework implementation of web services that wants to map XML messages onto classes and [WebMethods].
Sorry for the long rant and aploogies if you already know all of this. I feel like this is such a poorly understood distinction, so if this isn't for you then perhaps for others reading it.
-Brock DevelopMentor http://staff.develop.com/ballen
.
- Follow-Ups:
- Re: ByRef/Ref passing in Web Services
- From: Sahil Malik [MVP]
- Re: ByRef/Ref passing in Web Services
- From: Sahil Malik [MVP]
- Re: ByRef/Ref passing in Web Services
- Prev by Date: Re: Security framework
- Next by Date: Re: ByRef/Ref passing in Web Services
- Previous by thread: Target a different .NET Framework version
- Next by thread: Re: ByRef/Ref passing in Web Services
- Index(es):
Relevant Pages
|
