Logic App Send Message error with JSON

Question

I'm using Logic App to send a message to a service bus on Azure. The logic app starts with a HTTP Request for the trigger which contains a JSON payload in the body. The 'Body' of the request is set as the Content of the Send Message action. Since the payload is JSON when posting I set the Content-Type to application/json. This generates an error on the Send Message action;

{"code":"InvalidTemplate","message":"Unable to process template language expressions in action 'Send_message.' inputs at line '1' and column '1221': 'The template language function 'encodeBase64' expects its parameter to be a string. The provided value is of type 'Object'. Please see https://aka.ms/logicexpressions#encodeBase64 for usage details.'."}

So tried changing the Content-Type to text/plain and it works? Is this a bug or should convert the JSON to a text value somehow before using it in the Send Message action?

Szymon Wylezol Szymon Wylezol · Accepted Answer · 2016-07-15T19:53:16

Sending a message to service bus requires the message content to be base64 encoded. Since your content is a JSON, you would need to stringify it explicitly prior to encoding, i.e. use @encodeBase64(string(jsonContent))

Changing the content type to text/plain has the same effect, since in that case the content is treated as a string to begin with.

Logic App Send Message error with JSON

1 Answers