How to get query parameters in a Logic App?

First, you need to add your query param to the existing ones, e.g. 

https://xyz.logic.azure.com:443/workflows/id/triggers/manual/paths/invoke?api-version=2016-10-01&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=code&SelectedData="%7BsiteURL%3AXYZ.sharepoint.com%2Fsites%2FXYZDev%7D"

https://xyz.logic.azure.com:443/workflows/id/triggers/manual/paths/invoke
  ?api-version=2016-10-01
  &sp=%2Ftriggers%2Fmanual%2Frun
  &sv=1.0
  &sig=code
  &SelectedData="%7BsiteURL%3AXYZ.sharepoint.com%2Fsites%2FXYZDev%7D"

Then, you should be able to get them in your Logic App using 

@triggerOutputs()['queries']['SelectedData']

As you can see, there is no need to add a schema to the Http Trigger to get a query parameter


Context

  • MSFT Azure Logicapp
  • MSFT Logicapp workflow definition language
  • Live version as of 2020-06-25 04:56:31

Problem

  • Logicapp developer wants to obtain the value of a URL query parameter passed in via HTTP GET

Solution

  • The solution to this use-case is already provided elsewhere in this StackOverflow thread
  • This addon answer, however, refactors the previous solution
    • it addresses constructing expressions in MSFT Workflow definition language (the JSON-based source code you see when viewing a logicapp in "code" view)
    • it addresses the case where a missing name-value pair can cause the entire Logicapp to terminate. We do not want that to happen, so we process name-value pairs in an error-free way

Details

  • This URL extends the original question and another answer in this SO Thread
  • Here we expect FirstName LastName and FaveColor properties
    https://xyz.logic.azure.com:443/workflows/id/triggers/manual/paths/invoke
      ?api-version=2016-10-01
      &sp=%2Ftriggers%2Fmanual%2Frun
      &sv=1.0
      &sig=code
      &FirstName=Huomer
      &LastName=Huimpson
      &FaveColor=
  • Standard init: The following is sufficient to capture the desired name-value pairs
triggerOutputs()['queries']['FirstName']
triggerOutputs()['queries']['LastName']
triggerOutputs()['queries']['FaveColor']
  • Error-trap init: The following is sufficient to capture the desired name-value pairs without throwing an error if any desired name-value pair is missing (error-free capture)
triggerOutputs()['queries']?['FirstName']
triggerOutputs()['queries']?['LastName']
triggerOutputs()['queries']?['FaveColor']
  • Error-trap init with defaults: The following is sufficient to error-trap init the desired name-value pairs, as well as provide a default value for any missing values
coalesce(triggerOutputs()['queries']?['FirstName']  , 'Puomer'  )
coalesce(triggerOutputs()['queries']?['LastName']   , 'Puimpson' )
coalesce(triggerOutputs()['queries']?['FaveColor']  , 'Purple' )

Solution refactored

  • Consequently, the original solution can be refactored as follows
## BEFORE
@triggerOutputs()['queries']['SelectedData']

## AFTER
@{coalesce(triggerOutputs()['queries']?['SelectedData'] , '__blank__')}
  • This approach does what the typical use-case calls for, which is:
    • get the value if it exists,
    • otherwise provide a default value, and
    • don't crash the entire logicapp if the parameter was completely omitted
    • the @{} syntax can be used if you are editing workflow definition language directly, but not if you are entering it in the "expression dialog box"

See also

  • https://stackoverflow.com/a/51058306/42223
  • How to do a 'null' check in 'if' condition action of Azure Logic App
  • https://docs.microsoft.com/en-us/azure/logic-apps/workflow-definition-language-functions-reference#coalesce

Tags:

Azure

Azure Logic Apps

Workflow Definition Language

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