Logic Apps – Json Schema Verify

Logic Apps has got a really handy trigger : Request/Response.
It provides a public URL that you can post to, and takes an optional Json Schema.  The benefit of providing a Json schema is purely that the fields defined in the schema are then accessible throughout the Logic App workflow for interaction with other actions.
This is awesome, it really makes the Visual aspect of the designer work well –  but being picky – there’s no built in validation of the Json Request against the schema you provide.

I’ve got a pretty well defined Json schema that uses

  • Required Fields
  • Typed fields (string/integer/etc)
  • Regex patterns for strings

As such i’m pretty keen to first find out if the Json in the request is actually valid.  If it’s not – I can return a 400 pretty quickly to the caller and save some valuable cash on my Logic Apps actions (Logic Apps Price Model).

The solution I went for was to wrap the Newtonsoft Json Schema library in an Azure Function.

First complication is passing in two parameters to an Azure function (the json from the Request body and the Json Schema).  Both are needed in order to perform a schema validation, and the Azure function can’t reach out to Logic Apps.  Switch to Code View in the Logic App designer and use something like this;

Apart from that, the coding of the Azure function is pretty easy.
It’s in GitHub here https://github.com/Gordonby/AzFunctions/tree/master/JsonValidate, but here’s a snapshot of the files.

A simple implementation of this can be seen below.  A Request trigger which passes the body to my Function App, the Response then just relays in information provided by the output of the app.JsonSchemaValidate

XML to JSON data manipulation with schemas

Starting with an XML file and then working backwards… Old school data munging at it’s worst, and the tools/tips that I used.

Creating a XSD schema from XML
In Visual Studio 2015, open the XML file. Find the XML main menu and select Generate XSD.

Creating a JSON schema from XSD
This seems to be a bit of an issue at the moment. There’s an old BizTalk 2013 component that will create a json schema of a sort, but not a Rev4 one.
Unfortunately this seems to be best tackled manually at the moment.

Creating a JSON from XML
Here’s my process if you have the original XML.
Convert XML to JSON. I did this in visual studio using Newtonsoft JsonConvert.
Use JSON Lint/ to Validate and Format. You might also want to pull of any XML header info from the JSON at this point.
Look at the resulting JSON. If you’ve got properties beginning with “@” (they’re XML attributes), then you need to bin these characters off – I found it caused problems later.

Creating a JSON schema from JSON
http://jsonschema.net/#/

Verifying a JSON schema against JSON
http://jsonschemalint.com

Creating a Swagger definition file for a Logic App
http://gordon.byers.me/azure/creating-a-swagger-definition-for-an-azure-logic-apps-http-request-endpoint/

Creating a XSLT Map for an Azure Integration Account
Have a read about the Enterprise Integration Pack, Install the VS2015 extension https://aka.ms/vsmapsandschemas
Create a Biztalk Integration projects to be created then a Integration Map file which will allow you to visually map items between two XML schema files.
After building this project, an XSLT document is output into the bin folder.

Testing a Logic App HTTP Request Endpoint
https://chrome.google.com/webstore/detail/postman