"When a HTTP request is received" trigger breaks with SharePoint

[rrunnels]

I'm trying to build a Flow which populates a SharePoint List from a submitted web form using When a HTTP request is received.

The flow works fantastically until I add a SharePoint Create item trigger. Then, I immediately start getting a BadRequest error on the trigger with no other explanation. I've tried rebuilding from scratch but I get the error as soon I add the Create item action.

Do I need to add some kind of authentication to the request in order to use the SharePoint connection?

Any help would be much appreciated.

[rrunnels]

I found the problem - it was an issue with jQuery in the calling code. For anyone interested:

The $.ajax() function has a dataType property that I set to "json" thinking that it would automatically set the header's content-type, but it actually only sets the data type expected in the return. The default content-type is "application/x-www-form-urlencoded".

$.ajax({ 
    type: "POST", 
    url: $(this).attr("action"), 
    dataType: "json", 
    data: json_obj, 
})

This worked at first, but made the properties very difficult to access in Power Automate, which should have been my first clue. Then, of course, adding a SharePoint or SQL Server connector caused the whole flow to fail with BadRequest.

To solve the problem I added a contentType property set to "application/json" and converted the payload from a json object to a string:

$.ajax({
    type: "POST",
    url: $(this).attr("action"),
    dataType: "json",
    contentType: "application/json; charset=utf-8", // Set the content-type
    data: JSON.stringify(json_obj), // Stringify the output
})