Category: Pipelines


One of the core tenets of RESTFul architecture is that APIs should support content negotiation.  That is to say that the service consumer should be able to tell the service through the use of the Accept HTTP header what format the response message should be returned in.  On the flip side, it is commonly accepted that RESTFul APIs should support a range of request formats; typically XML and JSON at the very least, and that the Content-Type HTTP header is used to convey the format.

BizTalk Server 2013 R2 delivered the new JSON Decoder and Encoder pipeline components that at last treat JSON as a first class format in BizTalk Server.  Internally, BizTalk maps will still only work with XML as will a range of other BizTalk functions, however at the very least JSON is now accepted on the outskirts.  It is possible to get JSON support in older versions of BizTalk however you will have to create custom pipeline components to cater for this, since Microsoft has only added out of the box functionality in BizTalk Server 2013 R2.

Unfortunately, the traditional means of employing these pipeline components comes with some rigidity.  If you want to expose a RESTFul API using a WCF-WebHttp receive location then you will need to choose whether or not to include a JSON Decoder pipeline component in your receive pipeline.  On the flip side, you will need to choose whether to use a JSON Encoder on your send pipeline.  There is no way to dynamically decide whether to employ the JSON Decoder and Encoder based on the Content-Type and Accept header on the request message without employing an orchestration.  And it gets even worse…what if you wanted to build an API that also supported an HTML response type?

I’m not against the use of orchestration when they are used to provide some form of workflow or process orchestration, however I do not like being forced to use orchestration due to technical constraints.

I have addressed this problem for the most part using the BRE Pipeline Framework.  Because JSON decoding and encoding is only supported by BizTalk Server 2013 R2, I have addressed this problem in a custom MetaInstruction, or an extension to the framework, rather than making a change to the core framework.  Note that this extension requires that you have the BRE Pipeline Framework v1.6.0 or above installed on your machine.  This new functionality is catered for via the new BREPipelineFramework.JSONInstructions vocabulary.

Vocab

To get started download the installer for the extension and install it on your BizTalk 2013 R2 machine.  Install the vocabulary using the Business Rules Engine Deployment Wizard, the vocabulary file being found in the program files folder which by default is “C:\Program Files (x86)\BREPipelineFramework.JSONInstructions”.

Here’s a quick rundown on what these vocabulary definitions do.

  • DecodeJSON – This vocabulary definition executes the JSON Decoder against the message.  You will need to specify a root node name and namespace with which the decoded XML will be wrapped in.
  • EncodeJSON – This vocabulary definition executes the JSON Encoder against the message.  You will need to specify whether the root node will be stripped off prior to encoding or not.
  • ExecuteXSLTTransform – This vocabulary definition will execute an XSLT transformation based on an XSLT file which you must provide a file location for.  This is handy if you want to transform to/from HTML.
  • AssessContentType – This vocabulary definition lets you assess what the content type of your request message is so you can decide how to process it.  It will first attempt to derive the content type by studying the Content-Type HTTP header on the request.  If no Content-Type header is available then it will probe the first character of the message to determine if it is XML or JSON.
  • CacheAcceptHeader – Since we need to assess the Accept header value when choosing how to encode the response message, we must cache the Accept header value while processing the request.  If we did not do this then we would not have access to the value later.
  • AssessCachedAcceptHeader – This vocabulary definition lets you assess what the desired content type is based on the cached Accept header.  This can be executed on the send pipeline that is used to encode the response message.
  • GetCachedAcceptHeader – This vocabulary definition will return the raw value of the cached accept header.  This can be executed on the send pipeline that is used to encode the response message.  Only use this if you aren’t happy with the logic used by the AssessCachedAcceptHeader vocabulary definition.

The following screenshot demonstrates how we can dynamically decode incoming request messages based on the derived content type of the request message.  Note that if the message was XML instead of JSON then this rule would not first.  Note as well that we are caching the Accept header value for later use…theoretically this should be done in a separate rule which will execute regardless of the request content type but I have collapsed the two actions into one rule for brevity.

Rcv JSON

The following screenshot demonstrates the assessment of the cached Accept header value to dynamically encode the response message to JSON.

Snd JSON

And the next screenshot similarly dynamically transforms the response to HTML by executing custom XSLT.

Snd HTML

So how do you make use of this new vocabulary?  The easiest way to do this is to put the fully qualified class/assembly name of the custom MetaInstruction in the CustomMetaInstructionSeparatedList parameter (which takes in a ; delimited list) of the BREPipelineFrameworkComponent pipeline component as below.  Once you’ve done this then the vocabulary will be available for use in the ExecutionPolicy.

PC Config

The fully qualified class/assembly name value for the JSON extension is as below.

BREPipelineFramework.JSON.JSONMetaInstruction, BREPipelineFramework.JSON, Version=1.0.0.0, Culture=neutral, PublicKeyToken=83eab0b166470ebc

So what are the shortcomings of the current solution?

  • The response content type derivation based on the cached Accept header doesn’t currently go as far as is normally expected by RESTFul standards.  These standards dictate that multiple content types can be specified and each can be given priority weightings.  The solution I’ve put in place is just a v1, and it will always prioritize as follows regardless of explicit priorities – JSON > XML > URLEncodedForm > CSV > HTML > Text > Other.  If you don’t like this logic then you can always make your own choice by assessing the raw Accept header value with the GetCachedAcceptHeader vocabulary definition instead of the AssessCachedAcceptHeader vocabulary definition.
  • I have not yet found a context driven way of overriding the Content-Type HTTP header on the response message.  This will always be set to Application/XML, unless you have set an alternate value on the Messages tab of your receive location’s configuration in which case it will always be that alternative value.  For now the only way I can think of overriding this is via a WCF behavior.
  • It only works with BizTalk Server 2013 R2, but you could easily get it to work with BizTalk 2013 by creating your own custom MetaInstruction and vocabulary, and for the most part you can just reuse my own code except in your MetaInstruction you reference your custom JSON encoding/decoding pipeline components.  You can find the source code for the extension at “$/BREPipelineFramework/Main/BREPipelineFramework.BizTalk2013.R2/BREPipelineFramework.JSON” in the BRE Pipeline Framework source code repository.
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I have just released v1.6.0 of the BRE Pipeline Framework to the CodePlex project page.  The framework is now mature enough that it’s core has not changed much this time around, but there are still tons of new features and optimizations to be found in this version. For a recap on what the framework is all about you can read the primer or the provided documentation.

Before I dive into the new features, here are some steps to get started. If you’re installing the framework for the first time or upgrading from a version above v1.4.0 then all you need to do is download the installer, uninstall the previous version if applicable, run the new installer to completion, and then import the BREPipelineFramework.LatestVocabs.xml vocabulary definition file from the vocabulary subfolder in the program files folder (default location is C:\Program Files (x86)\BRE Pipeline Framework\Vocabularies).  If you are upgrading from a version older than v1.4.0 then you might be forced to stop your BizTalk host instances since older versions of the pipeline component were not signed with a strong named key and installed in the GAC.

Onto the new features.

HTTP Header Manipulation
The BREPipelineFramework.SampleInstructions.ContextInstructions vocabulary already has vocabulary definitions that allow you to read in the WCF.InboundHttpHeaders context property to read in inbound headers, or to set the WCF.HttpHeaders context property to set outbound headers. However what you’ll find is that reading or setting HTTP headers from these context properties is not exactly easy as each context property actually contains a delimited list of all the inbound or outbound HTTP headers as per the following example. Getting to an individual HTTP header can be tricky if you try to use these vocabulary definitions.

32d6f253-de53-4cf3-b559-1ec34ac1ad28
Important_User: True
Content-Length: 328
Content-Type: application/x-www-form-urlencoded
Expect: 100-continue
Host: servicebusrelaytest.servicebus.windows.net
Authorized_Token: 32d6f253-de53-4cf3-b559-1ec34ac1ad28" Namespace="http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties" Promoted="false" />

So now there is a new vocabulary called BREPipelineFramework.SampleInstructions.HttpHeaderInstructions which gives you the below vocabularies that allow you easier access to get or set inbound or outbound HTTP headers.
HTTPHeaderInstructions

The following screenshot demonstrates how these vocabulary definitions can be used. As you’ll see, you can read in inbound HTTP headers, explicitly set outbound HTTP headers, or copy inbound HTTP headers to outbound HTTP headers. You can set as many outbound HTTP headers as you want, and the framework will roll them all up into the single context property for you.
ExampleHttpHeader

Dynamic Pipeline Component Execution
This version of the framework now allows you to dynamically execute some of the out of the box Microsoft pipeline components. This feature was provided as a direct result of an issue posted on the framework’s page that asked for the ability to have context properties promoted on the target message when performing dynamic transformation using the framework. This would only really be possible by executing the XML Disassembler pipeline component, so the framework now has the ability to execute this component and some others.  You will be able to execute these pipeline components from within the new vocabulary BREPipelineFramework.SampleInstructions.PipelineInstructions.

PipelineInstructions

As you’ve seen in the previous screenshot, you can now execute the XML Assembler, XML DIsassembler, Flat File Assembler, Flat File Disassembler, and XML Validator pipeline components dynamically.  This means that you can assess conditions that allow you to decide whether/which pipeline components you should execute, and moreover you can dynamically configure parameters for these pipeline components as well.  The following screenshot demonstrates how you can execute the Flat File Disassembler while specifying the trailer schema parameter value.

FFDisassemble

One thing to note is that the BRE Pipeline Framework pipeline component is not a disassembler, so if you choose to execute a disassembler pipeline component and it ends up debatching an envelope message, the pipeline component will only pass through the first disassembled message.  In the case of the XML Disassembler, if you don’t want the message to be debatched you can make use of the DisassembleXMLMessagePropertyPromotionOnly vocabulary definition, which will result in context properties being promoted against the message without any debatching taking place.

Easier assertion of custom MetaInstructions

In the past, if you wanted to use your own custom MetaInstructions and corresponding vocabularies (see the project document page for more info on creating these) you would have to use an Instruction Loader Policy to assert the MetaInstruction fact so that it could be used in your Execution Policy (the BRE Policy in which you assess and manipulate your message’s context and content). In the following screenshot you’ll see how you a rule in an Instruction Loader Policy is used to assert a custom MetaInstruction fact into an Execution Policy by specifying the fully qualified class name and fully qualified assembly name of the MetaInstruction class.
InstructionLoaderPolicy
With v1.6.0 of the framework there is now a new pipeline component parameter called CustomMetaInstructionSeparatedList within which you can provide a semicolon separated list of fully qualified class/assembly names in the below format.

BREPipelineFramework.TestSampleInstructions.MetaInstruction, BREPipelineFramework.TestSampleInstructions, Version=1.0.0.0, Culture=neutral, PublicKeyToken=83eab0b166470ebc;BREPipelineFramework.TestSampleInstructions.MetaInstructionCopy, BREPipelineFramework.TestSampleInstructions, Version=1.0.0.0, Culture=neutral, PublicKeyToken=83eab0b166470ebc

This makes usage of custom MetaInstructions a whole lot easier to manage. You might still want to use an Instruction Loader Policy if any of the below scenarios applies to you.

  • You only want to conditionally assert the custom MetaInstruction in certain scenarios
  • You want to assert XML or SQL based facts
  • You want to conditionally override the ExecutionPolicy or the version

Assorted changes
There’s a couple more interesting new features across a variety of vocabularies.
In the BREPipelineFramework.SampleInstructions.CachingInstructions vocabulary, you’ll now find a vocabulary definition called GetCachedValueFromSSOConfigStore. The first time this vocabulary definition is executed it will read in a value from an SSO configuration store and it will also cache it. On further use of the vocabulary definition it will read the cached value rather than the SSO configuration store, keeping the number of hits to the SSO database to a minimum. By default the values will be cached for 30 minutes, but you can override this through the use of the UpdateCacheExpiryTime vocabulary definition in the same vocabulary.
CachedSSO
There is also a new vocabulary definition GetValueFromSSOConfigStore in the BREPipelineInstructions.SampleInstructions.HelperInstructions vocabulary which will read in a value from an SSO configuration store without caching the result. This is probably useful in scenarios where you expect that you will be updating the configuration values regularly and always want to be reading in the latest value.
There are two new vocabulary definitions in the BREPipelineFramework.SampleInstructions.XMLTranslatorInstructions vocabulary that allow you to remove an element and all child elements from the XML message being processed, in a fully streaming manner. These are the RemoveElementAndChildrenByName and RemoveElementAndChildrenByNameAndNamespace vocabulary definitions. An example of their usage is below. No exception will be thrown in an element matching the criteria you set is not found in the message, so this vocabulary can be used liberally.
RemoveElementAndChildren
There are also two new vocabulary definitions ReturnFirstRegexMatchInString and ReturnRegexMatchInStringByIndex that allow you to run regular expressions against strings (these can be any strings, you could potentially chain together vocabulary definitions to run the regular expression against a context property for example).
V1.6.0 of the framework also has more tracing all over the place which will make it easier to understand what is going on within your BRE rules.

Optimizations

Finally, there have been some optimizations made to the framework. All reflected types for custom MetaInstructions and maps being executed dynamically will now be cached rather than having their types reflected every single time. This results in improved runtime performance of the framework.

In a recent post I mentioned how you could dynamically set HTTP headers on a WCF-WebHttp send port.  This post will take this a bit further and discuss how you can dynamically set the target endpoint address as well as the HTTP method.

First things first, just as I mentioned in the post about HTTP headers, you must ensure that the BTS.IsDynamicSend context property is set to true to enable the methods I am about to describe.

Overriding the endpoint address is a piece of cake.  Just set the BTS.OutboundTransportLocation context property to the target URL.

    public Microsoft.BizTalk.Message.Interop.IBaseMessage Execute(IPipelineContext pContext, Microsoft.BizTalk.Message.Interop.IBaseMessage pInMsg)
    {
        // Some non important logic here

        pInMsg.Context.Write("OutboundTransportLocation", "http://schemas.microsoft.com/BizTalk/2003/system-properties", "http://target.service.com/parameters/go/here");
        pInMsg.Context.Write("IsDynamicSend", "http://schemas.microsoft.com/BizTalk/2003/system-properties", true);
        return pInMsg;
    }

Overriding the HTTP method took a bit more trial and error.  In order to achieve this you must set the WCF.HttpMethodAndUrl to the desired HTTP method.

    public Microsoft.BizTalk.Message.Interop.IBaseMessage Execute(IPipelineContext pContext, Microsoft.BizTalk.Message.Interop.IBaseMessage pInMsg)
    {
        // Some non important logic here

        pInMsg.Context.Write("HttpMethodAndUrl", "http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties", "POST");
        pInMsg.Context.Write("IsDynamicSend", "http://schemas.microsoft.com/BizTalk/2003/system-properties", true);
        return pInMsg;
    }

So what exactly does this context property represent and why is it named Method and URL?  This context property represents the value that would normally be contained in the HTTP method and URL mapping section of a WCF-WebHttp send port’s configuration.
MethodAndUrlMapping

If you inspect the help text underneath the textbox in the above screenshot you’ll notice that there are ways to set the HTTP method and URL mapping in this configuration.

  • By hardcoding the HTTP method in the text box such that every message being processed by the send port will have the same HTTP method.
  • By dynamically setting it (and the URL parameters as well) based on the XML BtsHttpUrlMapping configuration based on the value of the BTS.Operation context property on the message being processed.

Whatever value you have in the HTTP method and URL configuration of your send port will be put into the WCF.HttpMethodAndUrl context property on your message before it gets handled by the WCF adapter stack, which will apply the correct HTTP method and outbound URL.

So back to overriding the method, by setting a value to the WCF.HttpMethodAndUrl context property and ensuring that the HTTP method and URL configuration on the send port is blanked out, we are able to dynamically set the HTTP method on the outbound message.

I would be negligent if I didn’t mention that setting these two context properties (and BTS.IsDynamicSend) is a piece of cake when using the BRE Pipeline Framework which has out of the box capabilities to set these context properties. Being rules based, you can inspect the messages that are being processed and dynamically decide what the outbound URL and HTTP method should be based on message content and/or context.
BRE

Theoretically we could even dynamically set the WCF.HttpMethodAndUrl context property value to contain a BtsHttpUrlMapping XML instance so that we could dynamically set the HTTP method and URL based on the BTS.Operation context property value.  Given that it is a lot easier to just set the BTS.OutboundTransportLocation and WCF.HttpMethodAndUrl context properties to set the HTTP method and URL dynamically, this method is just too complicated to have its usage justified in most scenarios.

Ricardo Marques from Codit wrote a fantastic blog post a few years ago about dynamically setting HTTP headers for the WCF-WebHttp adapter using dynamic send ports in BizTalk Server based on the WCF.HttpHeaders context property. At the end of the article he stated that static send ports would not respect this context property, and this statement is the topic of this blog post.

Let me start by saying that I personally dislike dynamic send ports. It’s not that I don’t like the idea behind them, it’s more that I dislike the implementation (I won’t go into my reasons today). Wherever possible I will seek a way to enforce dynamic behavior on a static send port instead, and I have found a way to do this for dynamic HTTP headers.

The trick is super easy. All you need to do is set the BTS.IsDynamicSend context property value to true on the message before it gets processed by your WCF-WebHttp send adapter in order for it to respect the values in your WCF.HttpHeaders context property without losing access to all the other configuration you have set up on the static send port. I’ve extended the example provided in Ricardo’s original post below to illustrate how you set the context properties.

    public Microsoft.BizTalk.Message.Interop.IBaseMessage Execute(IPipelineContext pContext, Microsoft.BizTalk.Message.Interop.IBaseMessage pInMsg)
    {
        // Some non important logic here

        pInMsg.Context.Write("HttpHeaders", "http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties", "content-type: application/atom+xml");
        pInMsg.Context.Write("IsDynamicSend", "http://schemas.microsoft.com/BizTalk/2003/system-properties", true);
        return pInMsg;
    }

The inspiration to try this context property came from my colleague James’ blog post. His post was written regarding BizTalk 2009 so it’s good to see that Microsoft have been consistent about the usage of this context property even with the latest adapters. Thanks to both Ricardo and James for your good write-ups 🙂

I have just released a new version v1.5.5 of the BRE Pipeline Framework to the CodePlex project page.  This is a relatively minor update in that it only adds some missing WCF context properties to the enumerations used to get and set WCF context properties.

What makes this minor update important is that most of these context properties are REST related, and will enable you to build flexible REST based integration solutions where you can dynamically set HTTP methods, URLs, or headers.  The list of context properties added to the enumeration is below.

  • HttpHeaders
  • HttpMethodAndUrl
  • InboundHttpHeaders
  • InboundHttpMethod
  • InboundHttpStatusCode
  • InboundHttpStatusDescription
  • IssuerName
  • IssuerSecret
  • OutboundHttpStatusCode
  • OutboundHttpStatusDescription
  • StsUri
  • SuppressMessageBodyForHttpVerbs
  • VariablePropertyMapping

This new version is fully backwards compatible, and installing it will only require uninstalling the previous version from the add/remove programs control panel and then running the new installer.  Please post any issues/feedback/comments to the CodePlex project discussions page.

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