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Azure Logic Apps

Historically working with BizTalk has been overly difficult. Once you get past very simple scenarios, the learning curve for BizTalk was so steep that most developers didn’t even bother trying. They would either hack something together or just skip BizTalk entirely and just use purely custom code.

Microsoft’s intends to fix this problem with what they are calling “Logic Apps”. Like BizTalk before it, Azure Logic Apps are focused on integration scenarios. The first thing you’ll notice is the large number of connectors to popular services such as Twitter and Dropbox in addition to the usual database and HTTP-based connectors.

API connectors such as the aforementioned Twitter connector use OAuth to generate a client token. Each API connector defines its own list of available actions for App Logic to consume. This is exposed to Azure using the REST API definition standard swagger. Like WSDL for the WS-* stack, applications can parse the API definitions and automatically generate a simple user interface.

Workflows need to be triggered by something. Some triggers are simply timer based, others watch for new data from connectors. And interesting feature of triggers in App Logic is that they are stateful. This allows your triggers to conditionally perform actions based on what it did previously.

By default, each action after the first is implicitly triggered when the previous action completes successfully. Developers may explicitly state the dependencies, which may be conditional based on expressions in the data.

Actions can be marked as repeated. When this is turned on, it acts like a for-each loop over the items returned from the previous action.

In the demo, Microsoft showed piping the result of a Twitter search into files on Dropbox. This requires the Dropbox action to have an understanding of the data pulled from the Twitter step. This can be done using notation known as Template Language Extensions. A first glance it looks like X-Path, but it is designed to work on JSON data formats.

App Logic and Visual Studio

If you don’t like working with the visual designers in Azure, you can create your workflows in Visual Studio. When working in that environment, you’ll be working on JSON-based workflow definitions in raw text format.

For more information on Microsoft’s replacement for BizTalk, watch the Channel 9 video Logic Apps.

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