I need to retrieve binary (non-XML) documents as Messages in a custom WCF LOB Adapter (for consumption by BizTalk). The messages need to be represented as instances of System.ServiceModel.Channel.Message.
I can't find how to create an instance of this class when the content is binary (by "binary" I mean any arbitrary byte array or Stream, and not only binary representations of XML documents).
Is this possible? Or would wraping the binary contents in an XML enveloppe be the only way to do this in WCF?
Fundamentally, WCF messages are XML, since the S.S.C.Message class uses the Xml InfoSet as the base message representation.
So yes, in some way you need to "wrap" your binary content into an XML envelope (which doesn't need to be a SOAP envelope, mind you, depending on how your binding is configured).
That said, note that this doesn't preclude streaming to deal with large message payloads without buffering the entire message in memory; WCF still allows you to do this, though sometimes it's not greatly obvious how it works.
Since you're working with a custom channel, you've got one of two choices, I think:
Have your own channel add the XML wrapper around your binary content before passing it upwards or
Create a custom MessageEncoder that adds it in for you automatically.
In either case, if you're dealing with large messages, you'll want to make sure you use the MessageEncoder overloads that handle Streams instead of buffers, as they are the ones that give you the option of doing coordinated streaming with the service implementation.
WCF offers some ways to send binary attachments and stream data in various ways. We have an application at work that does this, but I haven't had a chance to dig through the code, so I can't offer too much help. Here are a few links that might get you started (Nicholas Allen's Indigo Blog is a great place for WCF info):
http://blogs.msdn.com/drnick/archive/2006/03/31/565558.aspx
http://weblogs.asp.net/cibrax/archive/2007/08/29/sending-attachments-with-wcf.aspx
Related
I'm developing an app using MonoTouch and have to get some data from a 3rd party web service. I have a WCF binding to do such.
The particular web service method I am calling could potentially return an XML string in the range of several hundred megabytes, which could take a while to download to a mobile device.
I'm looking for some way to capture how many bytes have been read from the network at the system level, with the end-game being to display a progress indicator to the user. Is there some way I can achieve this using Behaviors?
Note, I don't have any way to modify the web service code to return a Stream object, which is what most of the articles I have found require doing.
Any help or direction would be much appreciated. Thanks
As a last resort, I can always fall back on using an NSURLConnection to do this, instead of WCF, because I know there are NSURLConnectionDelegate methods to hook into that will provide this. I wanted to avoid NSURLConnection, so that I will be able to easily drop this code into an Android project in the future.
Is there a reason to use WCF instead of the plain HttpWebRequest?
WCF is not exactly efficient at parsing data, it will keep multiple copies in memory to deserialize the various chunks of information.
There is no system level API that can provide this information, the Stream that you get back from the HttpWebRequest is the best value that you will get.
I am still confused when it is appropriate to use the Message type in WCF like below
[ServiceContract]
public interface IMyService
{
[OperationContract]
Message GetData();
[OperationContract]
void PutData(Message m);
}
Why would you want to use it?
Can you use it for streaming?
Thanks
MSDN lists the follow reasons for using the message class directly:
When you need an alternative way of creating outgoing message contents (for example, creating a message directly from a file on disk) instead of serializing .NET Framework objects.
When you need an alternative way of using incoming message contents (for example, when you want to apply an XSLT transformation to the raw XML contents) instead of deserializing into .NET Framework objects.
When you need to deal with messages in a general way regardless of message contents (for example, when routing or forwarding messages when building a router, load-balancer, or a publish-subscribe system).
See Using the Message Class for more detailed information.
Edit to address the streaming question
I didn't find a definitive answer in my quick scan via google, but the article above states "All communication between clients and services ultimately results in Message instances being sent and received" - so I would assume it could be used directly in streaming.
While the reasons listed by Tim are valid, we use messages directly in our services to create one uber routing service.
we have one service that can take any method call you throw at it, Clients are generated by wsdls supplied from multiple sources.
This service would take the message, examine its content and route it accordingly.
So in my opinion if you want to get closer to the wire, or when you dont know the type of incoming messages, you can use the message in the signature directly.
Streaming is a separate concept than message signature, streaming is supported by wcf under very specific bindings and security mechanism and the method signature has to be very specific (i.e it should return/accept stream). Also in streaming the actual stream of data travels outside the scope of soap message.
All, can anyone provide me some guidance on allowing NServiceBus to consume XML messages off a queue that were not created by NServiceBus. I am trying to integrate with a 3rd party system that drops XML messages to a queue. I have VERY little control over the XML the 3rd party produces.
I have tried wrapping their XML with the -Messages/- tag and I can get the message to hit the right handler, but many of the fields (especially in child classes) just deserialize to null. The 3rd party produces several "types" of messages but in all cases the XML is reasonably simple.
I'm trying to avoid writing an adapter that just reads XML and drops messages on the bus.
Any advise would be appreciated.
Thanks
The key lies in how you generate the message classes. If you can, you should get the XSD schemas from the third party that represent the XMLs they are sending you.
Then you can generate classes off the schemas using xsd.exe which will pretty much guarantee clean de-serialisation from XML to type.
If you can't get the schemas then you can again use xsd.exe to infer the schemas from the messages. However this method is not particularly fail-safe, and will expose you negatively to anything unexpected the message which does not conform to your inferred schema.
The serialization in NSB is abstracted so you could write your own serializer based on that format. You can then tell NSB to use your serializer instead of one of the built in ones.
ON what basis should we decide whether we have to create a dataContract or a MessageContract for my WCF services.
What I know is that when we need to have more control over SOAP,We use MessageContract.
Secondly I have seen some code in which DataContract is exposed through MessageContract.Whats the use of it.
Please provide some real life scenerios.
It's not an "either-or" question - you'll always have data contracts if you're dealing with compound data (more than just the basic types of int, string etc.). That's a given.
You'll only ever need message contracts if you need to very closely and very specifically control the layout of your SOAP messages. In most case, over 90% of the time - you don't.
A message contract allows you to specifically say which elements (scalar types or compound types as DataContracts) will be in the SOAP header, and which will be in the SOAP body.
You might need this if you have a communication partner which requires a very specific format and you have to tweak your SOAP messages to match that given layout exactly. That's just about the only valid scenario when you'll need to and should use message contracts.
So, to make a long story short: always use data contracts, practically never use message contracts (unless you absolutely, positively have to).
Marc
If you need to take over the SOAP headers and body explicitly, you would use MessageContracts. For example, if you needed to make sure a credit card number was encrypted in your message separately from the rest of your type, you'd need to get that level of control over the message on the wire.
Here's more information on that with some examples (specifically the encryption example): http://msdn.microsoft.com/en-us/library/ms730255.aspx
If you just want pure DTOs and don't care about their shape on the wire, go with DataContracts.
I'm looking to use the MsmqIntegrationBinding to integrate with a legacy queue which has a serialized object as the message body. Has anyone come up with a way to obtain the "metadata" of the message body and create a service side class to use within the service?
For example, if I put in a serialized Product object from System A and my service needs to consume it, how do I provide MsmqMessage the type if I do not have the Product class on my side? I was thinking of reading off a message in a separate program, deserializing, and then emitting via the code dom. Ideas?
I wholeheartedly recommend against attempting to emit the deserialized type at runtime in the message destination. Either work with the XML at the destination to obtain the data you desire, or build data contracts that both the source and destination can adhere to.
Hmm... in WCF, you can define service methods which take (and optionally return) an untyped Message type. This seems to fit your bill quite nicely.
Other than with strongly typed messages, you'll have to do all the putting together of the message on the client and the taking apart on the server by means of reading the raw XML - but that seems to be what you're looking for, right?
Find more information and samples here:
WCF - Handling Generic Messages
How to pass a generic object through WCF
Untyped messages on WCF
Untyped messages have some restrictions, e.g. you can only read them once on the server, but you should be able to manage your scenario with this, I think.
Marc