Hi Guys : It seems like the SOAP/WSDL world was very high on generating objects from data models, but I cannot tell wether the REST approach to web services favors the same approach. In my opinion, it seems as though JSON is emerging as the new common, native object format for most languages, thus obviating any need for language specific APIs. However, I'm new to the web services game.
Thus my question is : Are there tools which can autogenerate REST client side objects for us? And secondarily, is it customary in the web-services world, to provide client side objects for dealing with REST data (as is neccessary for dealing with SOAP data) ?
What the "REST world" doesn't quite have in the same way as the "SOAP world" is a service description language like WSDL. At least, it's not quite as uniform.
There is of course HTML. Behind REST is the Web, and it would be unfair to dismiss HTML, since it has precisely the purpose of describing what you can do with the service. The downside is that it's not very computer-friendly in its most common form. Hence, there is no html2java that will turn your forms into objects. In addition, the programming model would be quite different to remote objects, which tools like wsdl2java tend to incur.
There is WADL, but it's not necessarily wide-spread. There is a wadl2java tool (see this question too perhaps).
It also depends on what you call a "REST" web service: does it really make proper use of the hypermedia, or is it just sending XML/JSON to a nice-looking URL.
and thank you for reading.
I am implementing a WCF Service based on a predefined specification (HR-XML 3.0). As such, I am starting with the schema, and working my way back to code. There are a number of large Schema documents (which import yet more Schema documents) related to my implementation, provided by this specification.
I am able to generate code using xsd.exe, by supplying the "main" and "supporting" xsd files as arguments. But there are several issues, and I am wondering if this is the right approach.
there are litterally hundreds of classes - the code file is half a meg in size
duplicate classes (ex. Type, Type1 - which both represent the same type)
there are classes declared as inheriting from a base class, but that base class is not generated/defined
I understand that there are limitations to the types of Schema supported by svcutil.exe/xsd.exe when targeting the DataContractSerializer and even XmlSerializer. My question is two-fold:
Are code generation "issues" fairly common when dealing with larger, modular xsd files? Has anyone had success with generating data contracts from OAGIS or HR-XML schema?
Given the above issues, are there better approaches to this task, avoiding generating code and working with concrete objects? Does it make better sence to read and compose a SOAP message directly, while still taking advantage of the rest of the WCF framework? I understand that I am loosing the convenience of working with .NET objects, and the framekwork-provided (de)serialization; given these losses, would it still be advantageous to base my Service on WCF? Is there some "middle ground" between working with .NET types and pure XML?
Thank you very much!
-Sasha Borodin
DFWHC.org
Sasha, If you are going to use code generation, you likely should never start with the modular schemas. When you put a code generator against the modular schemas, you'll generate a class for all the common compoents in the HR-XML library and a good bit of the common components in OAGIS. You don't want this. HR-XML is distributed with standalone schemas, which are a better starting point. An even better starting point would be to create a flattened package xsd containing only the types brought in by the WSDL. If you use a couple standalone schemas, you are going to at least have some duplications among your generated code.
Well, you could try and do something like this:
convert your XSD to C# code separately, using something like the xsd.exe tool from Microsoft, or something like Xsd2Code as a Visual Studio Plugin.
Xsd2Code in Visual Studio http://i3.codeplex.com/Project/Download/FileDownload.aspx?ProjectName=Xsd2Code&DownloadId=41336
once you have your C# classes, weed out any inconsistencies, duplications, and so forth
package everything up into a separate class library assembly
now, when generating your WCF service from the WSDL, either using Add Service Reference from Visual Studio or the svcutil.exe tool, reference that assembly with all the data classes. Doing so, WCF should skip re-creating the whole set of classes again, and use whatever is available in that data assembly
With this, you might be able to get this mess under control.
I've a Silverlight 3 based project, talking with a DB via a WCF web service. So far, so good.
I'm growing more and more concerned about the sheer number of xsd and wsdl files generated in the servicereference subfolder.
The increasing numbers seems to be a kind of versioning, but I'm not sure...
Do you know what is it for? It seems not to be included in the resulting .xap...
where may I find an article on this stuff?
It's not really bloat. When WCF generates WSDL it references external documents. Supposedly, this is the proper way to do it, but enough programming stacks choke on it that multiple people have come up with ways of flattening the WSDL.
You can read all about the Service Description at: http://msdn.microsoft.com/en-us/library/aa738723.aspx
I am trying to create a WCF service in JScript.NET. (I know, I should do it in C# or VB.NET, but humour me, please.) Has anyone done this before?
I can create .asmx web services, but I'm not sure how I have to modify web.config to make the .svc file work -- do I need to precompile things?
Also, I am (for right now) trying to do this using inline code -- is this feasible, or do I really need a code-behind if I'm doing things by hand...
Thanks!
You are going to need a code behind. The model for creating services in WCF is drastically different than the .asmx model for web services (WCF services are actually more than that).
And while you can do contract-first development with WCF services (which would prevent you from having to define interfaces and attributes, somewhat), some of WCF's power comes from using code constructs to define your contract. I don't think that this will be easy in a language like JScript. You might be able to get away with the actual implementation, but I think the contract definitions are going to be an issue for you if you use JScript.
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I understand the value of the three-part service/host/client model offered by WCF. But is it just me or does it seem like WCF took something pretty direct and straightforward (the ASMX model) and made a mess out of it?
Is there an alternative to using SvcUtil's command line step back in time to generate the proxy? With ASMX services a test harness was automatically provided; is there a good alternative today with WCF?
I appreciate that the WS* stuff is more tightly integrated with WCF and hope to find some payoff for WCF there, but geeze, otherwise I'm perplexed.
Also, the state of books available for WCF is abysmal at best. Juval Lowy, a superb author, has written a good O'Reilly reference book "Programming WCF Services" but it doesn't do that much (for me anyway) for learning now to use WCF. That book's precursor (and a little better organized, but not much, as a tutorial) is Michele Leroux Bustamante's Learning WCF. It has good spots but is outdated in place and its corresponding Web site is gone.
Do you have good WCF learning references besides just continuing to Google the bejebus out of things?
Okay, here we go. First, Michele Leroux Bustamante's book has been updated for VS2008. The website for the book is not gone. It's up right now, and it has tons of great WCF info. On that website she provides updated code compatible with VS2008 for all the examples in her book. If you order from Amazon, you will get the reprint which is updated.
WCF is not only a replacement for ASMX. Sure it can (and does quite well) replace ASMX, but the real benefit is that it allows your services to be self-hosted. Most of the functionality from WSE has been baked in from the start. The framework is highly configurable, and the ability to serve multiple endpoints over multiple protocols is amazing, IMO.
While you can still generate proxy classes from the "Add Service Reference" option, it's not necessary. All you really have to do is copy your ServiceContract interface and tell your code where to find the endpoint for the service, and that's it. You can call methods from the service with very little code. Using this method, you have complete control over the implementation. Regardless of the method you choose to generate a proxy class, Michele shows both and uses both in her excellent series of webcasts on the subject.
Michele has tons of great material out there, and I recommend you check out her website(s). Here's some links that were incredibly helpful for me as I was learning WCF. I hope that you'll come to realize how strong WCF really is, and how easy it is to implement. The learning curve is a little bit steep, but the rewards for your time investment are well worth it:
Michele's webcasts: http://www.dasblonde.net/2007/06/24/WCFWebcastSeries.aspx
Michele's book website (alive and updated for VS2008): http://www.thatindigogirl.com/
I recommend you watch at least 1 of Michele's webcasts. She is a very effective presenter, and she's obviously incredibly knowledgeable when it comes to WCF. She does a great job of demystifying the inner workings of WCF from the ground up.
I typically use Google to find my WCF answers and commonly find myself on the following blogs:
Blogs with valuable WCF articles
http://blogs.msdn.com/drnick/default.aspx
http://blogs.msdn.com/wenlong/default.aspx
http://blogs.thinktecture.com/buddhike/
http://www.dasblonde.net/default.aspx
Other valuable articles I've found
http://blogs.conchango.com/pauloreichert/archive/2007/02/22/WCF-Reliable-Sessions-Puzzle.aspx
http://blogs.msdn.com/salvapatuel/archive/2007/04/25/why-using-is-bad-for-your-wcf-service-host.aspx
I'm having a hardtime to see when I should or would use WCF. Why? Because I put productivity and simplicity on top of my list. Why was the ASMX model so succesful, because it worked, and you get it to work fast. And with VS 2005 and .NET 2.0 wsdl.exe was spitting out pretty nice and compliant services.
In real life you should have very few communication protocols in your architecture. This keeps it simple an maintainable. If you need to acces to legacy systems, write specific adapters for them so they can play along in the nice shiny and beautiful SOA world.
WCF is much more powerful than ASMX and it extends it in several ways. ASMX is limited to only HTTP, whereas WCF can use several protocols for its communication (granted, HTTP is still the way most people will use it, at least for services that need to be interoperable). WCF is also easier to extend. At least, it is possible to extend it in ways that ASMX cannot be extended. "Easy" may be stretching it. =)
The added functionality offered by WCF far outweighs the complexity it adds, in my opinion. I also feel that the programming model is easier. DataContracts are much nicer than having to serialize using XML serialization with public properties for everything, for example. It's also much more declarative in nature, which is also nice.
Wait.... did you ever use .NET Remoting, cause thats the real thing its replacing. .NET Remoting is pretty complicated itself. I find WCF easier and better laid out.
I don't see it mentioned often enough, but you can still implement fairly simple services with WCF, very similar to ASMX services. For example:
[ServiceContract]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class SimpleService
{
[OperationContract]
public string HelloWorld()
{
return "Hello World";
}
}
You still have to register the end point in your web.config, but that's not so bad.
Eliminating the verbosity of the separated data, service, and operation contracts goes a long way toward making WCF more manageable for me.
VS2008 includes the "Add Service Reference" context menu item which will create the proxy for you behind the scenes.
As was mentioned previously, WCF is not intended solely as a replacement for the ASMX web service types, but to provide a consistent, secure and scalable methodology for all interoperable services, whether it is over HTTP, tcp, named pipes or MSMQ transports.
I will confess that I do have other issues with WCF (e.g. re-writing method signatures when exposing a service over basicHTTP - see here, but overall I think it is a definite imrovement
If you're using VS2008 and create a WCF project then you automatically get a test harness when you hit run/debug and you can add a reference without having to use svcutil.
My initial thoughts of WCF were exactly the same! Here are some solutions:
Program your own proxy/client layer utilising generics (see classes ClientBase, Binding). I've found this easy to get working, but hard to perfect.
Use a third party implementation of 1 (SoftwareIsHardwork is my current favourite)
WCF is a replacement for all earlier web service technologies from Microsoft. It also does a lot more than what is traditionally considered as "web services".
WCF "web services" are part of a much broader spectrum of remote communication enabled through WCF. You will get a much higher degree of flexibility and portability doing things in WCF than through traditional ASMX because WCF is designed, from the ground up, to summarize all of the different distributed programming infrastructures offered by Microsoft. An endpoint in WCF can be communicated with just as easily over SOAP/XML as it can over TCP/binary and to change this medium is simply a configuration file mod. In theory, this reduces the amount of new code needed when porting or changing business needs, targets, etc.
ASMX is older than WCF, and anything ASMX can do so can WCF (and more). Basically you can see WCF as trying to logically group together all the different ways of getting two apps to communicate in the world of Microsoft; ASMX was just one of these many ways and so is now grouped under the WCF umbrella of capabilities.
Web Services can be accessed only over HTTP & it works in stateless environment, where WCF is flexible because its services can be hosted in different types of applications. Common scenarios for hosting WCF services are IIS,WAS, Self-hosting, Managed Windows Service.
The major difference is that Web Services Use XmlSerializer. But WCF Uses DataContractSerializer which is better in Performance as compared to XmlSerializer.
In what scenarios must WCF be used
A secure service to process business transactions. A service that
supplies current data to others, such as a traffic report or other
monitoring service. A chat service that allows two people to
communicate or exchange data in real time. A dashboard application
that polls one or more services for data and presents it in a logical
presentation. Exposing a workflow implemented using Windows Workflow
Foundation as a WCF service. A Silverlight application to poll a
service for the latest data feeds.
Features of WCF
Service Orientation
Interoperability
Multiple Message Patterns
Service Metadata
Data Contracts
Security
Multiple Transports and Encodings
Reliable and Queued Messages
Durable Messages
Transactions
AJAX and REST Support
Extensibility
source: main source of text
MSDN? I usually do pretty well with the Library reference itself, and I usually expect to find valuable articles there.
In terms of what it offers, I think the answer is compatibility. The ASMX services were pretty Microsofty. Not to say that they didn't try to be compatible with other consumers; but the model wasn't made to fit much besides ASP.NET web pages and some other custom Microsoft consumers. Whereas WCF, because of its architecture, allows your service to have very open-standard--based endpoints, e.g. REST, JSON, etc. in addition to the usual SOAP. Other people will probably have a much easier time consuming your WCF service than your ASMX one.
(This is all basically inferred from comparative MSDN reading, so someone who knows more should feel free to correct me.)
WCF should not be thought of as a replacement for ASMX. Judging at how it is positioned and how it is being used internally by Microsoft, it is really a fundamental architecture piece that is used for any type of cross-boundary communication.
I believe that WCF really advances ASMX web services implementation in many ways. First of all it provides a very nice layered object model that helps hide the intrinsic complexity of distributed applications.
Secondly you can have more than request-replay messaging patterns, including asynchronous notifications from server to client (impossible with pure HTTP), and thirdly abstracting away the underlying transport protocol from XML messaging and thus elegantly supporting HTTP, HTTPS, TCP and other. Backward compatibility with "1-st generation" web services is also a plus.
WCF uses XML standard as the internal representation format. This could be perceived as advantage or disadvantage, especially with the growing popularity "fat-free alternatives to XML" like JSON.
The difficult things I find with WCF is managing the configurations for clients and servers, and troubleshooting the not so nice faulted state exceptions.
It would be great if anyone had any shortcuts or tips for those.
I find that is a pain; in that I have .NET at both ends, have the same "contract" dlls loaded at both ends etc. But then I have to mess about with a lot of details like "KnownType" attributes.
WCF also defaults to only letting 1 or 2 clients connect to a service until you change lots of configuration. Changing the config from code is not easy, shipping lots of comfig files is not an option, as it is too hard to merge our changes into any changes a customer may have made at the time of an upgrade (also we don't want customers playing with WCF settings!)
.NET remoting tended to just work most of the time.
I think trying to pretend that .NET to .NET object based communications is the same as sending bit so of Text (xml) to an unknown system, was a step too far.
(The few times we have used WCF to talk to a Java system, we found that the XSD that the java system gave out did not match what XML it wanted anyway, so had to hand-code a lot of the XML mappings.)