Month: December 2020

The response is not in a JSON format

Have you been using the HTTP with Azure AD connector lately? It´s really a game-changer for me. No more custom connector is needed, unless you want to. I wrote a whole how-to post about it.

The problem

I was using the connector to access an on-prem web service, "in the blind". I had some information about the message that should be sent but was not sure. I was trying out different messages when I got this strange error back:

{
    "code": 400,
    "source": <your logic app's home>,
    "clientRequest": <GUID>,
    "message": "The response is not in a JSON format",
    "innerError": "Bad request"
}

Honestly, I misinterpreted this message and therein lies the problem.
I was furious! Why did the connector interpret the response as JSON? I knew it was XML, I even sent the Accept:text/xml header. Why did the connector suppress the error-information I needed?

The search

After trying some variants on the request body all of a sudden I got this error message:

{
    "code": 500,
    "message": "{\r\n  \"error\": {\r\n    \"code\": 500,\r\n    \"source\": \<your logic app's home>\",\r\n    \"clientRequestId\": \"<GUID>\",\r\n    \"message\": \"The response is not in a JSON format.\",\r\n    \"innerError\": \"<?xml version=\\\"1.0\\\" encoding=\\\"utf-8\\\"?><soap:Envelope xmlns:soap=\\\"http://schemas.xmlsoap.org/soap/envelope/\\\" xmlns:xsi=\\\"http://www.w3.org/2001/XMLSchema-instance\\\" xmlns:xsd=\\\"http://www.w3.org/2001/XMLSchema\\\"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring>Server was unable to process request. ---> Data at the root level is invalid. Line 1, position 1.</faultstring><detail /></soap:Fault></soap:Body></soap:Envelope>\"\r\n  }\r\n}"
}

And now I was even more furious! The connector was inconsistent! The worst kind of error!!!

The support

I my world, I had found a bug and needed to know what was happening. There was really only one solution: Microsoft support.
Together we found the solution but I still would like to point out that error message that got me off track.

The solution

First off! The connector did not have a bug, nor is it inconsistent; it is just trying to parse and empty response as a JSON body.
Take a look back at the error messages. They are not only different in message text, but in error code. The first one was a 400 and the other a 500. The connector always tries to parse the response message as JSON.

Error 500: In the second case (500) it found the response body, and supplied the XML as an inner exception. Not the greatest solution, but it works.
Error 400 In the first error message the service responded back with a Bad request and an empty body. This pattern was normal back when we built Web Services. Nowadays, you expect a message back, saying what is wrong. In this case, the connector just assumed that the body was JSON, failed to parse it and presented it as such.

If we take a look at the message again perhaps it should read:

{
    "code": 400,
    "source": <your logic app's home>,
    "clientRequest": <GUID>,
    "message": "The response-message was emtpy",
    "innerError": "Bad request"
}

Or The body length was 0 bytes Or The body contained no data

Wrapping up

Do not get caught staring at error messages. You can easily follow down the trap of assumptions. Verify your theory, try to gather more data, update your On-Premise Data Gateway to the latest version, and if you can: try the call from within the network, just like old times.

What is this?

I have found a new connector which is much better suited for calling OnPrem services from Logic Apps.

The use of a custom connector

A custom connector is meant to be a bridge between your Logic App and an on premise service, handling JSON or XMLSOAP. It can also be used as a way of minimizing the clutter in a confusing API and exposing only the necessary settings to your Logic App developer. You do not even have to access on premise services using the connector.

I have have some experience in setting up OnPrem integrations and have posted about Planning installation of the On Premise Gateway and finally solving how to deploy the Custom Connector using ARM.

A better connector

My use of the Custom Connector has always been to call OnPrem services that are either SOAP or JSON based. For that I have used a custom connector but there is a great alternative, if you know how to create XML Envelopes or JSON bodies. The only thing you will loose using this connector is the nice interface in the Logic App.

Let me point you to the HTTP with Azure AD connector, and yes you can use it with Azure AD but this post is about replacing your Custom Connectors.

The scenario

I have an OnPrem service that uses old school SOAP and XML to provide information about Customers. The service uses Windows Authentication and will respond with the given customer as an XML response.

If you don´t know SOAP: it is basically a HTTP POST with a header named SOAPAction and an XML body. I will show you a JSON call at the end as well.

Using the connector

Prerequisite: In order to access OnPrem services, you must install the OnPrem data gateway.

Add the connector to a Logic App

Add a new Action the same way as always, Search for HTTP with Azure AD. I know, it says Azure AD. It is strange but trust me.

Now look at the available Actions.

The first one will only use the GET HTTP verb. Choose the other one.
You will now get this scary image.

I know it says Azure AD but here comes the payoff. Click the Connect via On-premises data gateway checkbox.

TADAAAAA! You can now start filling in the settings for your service call, directly to the OnPrem Service without using a Custom Connector.

Configure the connector

Authentication Type

Start by choosing the Authentication Type. Note that the Username and Password fields are still visible, even if you choose Anonymous.
I will use Windows Authentication, which, by the way, is not supported in the Custom Connector.

Base Resource URL

This is the start path to your service URL as if it was called from within the OnPrem network.
A full service URL might look like this: http://webapiprod/EmployeeService/GetEmployee.asmx, then the base would be http://webapiprod/EmployeeService or http://webapiprod depending on how you want to slice it. The full service URL will be defined later. Also notice that you do not end the base url with a /.

I will call a service with the full path http://erpsystem/WebServices/GetCustomers.asmx so I opt for http://erpsystem/WebServices

Windows Authentication

This is very simple: enter the username (including domain) and password to the OnPrem user you need to use for authentication. I have entered the username and domain like this companydomain\erpwebusr

Gateway

Choose the appropriate subscription and gateway. I have to censor mine for obvious reasons.

Done

The final product looks like this:

Just click Create to start using it.

Start using the connector

I test a lot of APIs in its raw format, using Postman or HTTP RestClient with VS Code or even SOAPUI back in the day. I know how to format a message. I think you do too. I will now configure the connector to execute a call to the SOAP service to get Customer data.

Choose a Method

You have to choose the HTTP verb you need. For SOAP you always use a POST, but your service might need to use a GET.

Url of the request

Here you can either enter the full url or the last part depending on how you feel about either.
My full path was http://erpsystem/WebServices/GetCustomers.asmx and I opted for http://erpsystem/WebServices as the base path. Therefore I can either enter the full path, or be fancy and just enter /GetCustomers.asmx. I am fancy.

Headers

You need to add headers to your call. In the case of SOAP, you need SOAPAction, Content-type and lastly an Accept header.
The last one seems to tell the connector what data to expect back. If you do not set this to text/xml, the connector will expect a JSON message and give you a 400 Bad Request back.

If you call a Rest-service you will only need a content type if you supply a BODY.

You might also need to send additional headers, like API-keys and such. Simply add the ones you need.

Add headers by clicking the Add new parameter dropdown.

Select Headers and fill in the headers you need, depending on your needs. For SOAP these are located in the WSDL-file.

I need to set SOAPAction: GetCustomer, Content-type: text/xml and Accept: text/xml

Body of the request

If you are calling a SOAP service or sending data to a rest service, you need to set the body. This Connector even supports XML in the designer. So simply supply the XML you need to execute your call. I must send this:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:get="http://erpsystem/webservices/GetCustomers" xmlns:cus="http://myns.se/customer" xmlns:man="http://www.erpsystem.com/Manager">
   <soap:Header/>
   <soap:Body>
      <get:Execute>
         <get:request>
            <get:_requests>
               <get:GetCustomers>
                  <cus:customer_Id>XXXX</cus:customer_Id>
               </get:GetCustomers>
            </get:_requests>
         </get:request>
      </get:Execute>
   </soap:Body>
</soap:Envelope

I know. SOAP was not aimed at being lightweight.
The XXXX part will be replaced by the customer ID sent to the Logic App.

The end product looks like this:

The Accept header is missing in the picture. It is from an earlier version of this post.

Calling the backend service

A call to the service might look like this (I blocked out some sensitive things):

Looking at the call

Please note that the Body of the request is always sent as a Base64 encoded. This means that you need to have access to a decoder to read what you actually sent. It also means that the service you are calling must accept Base64 encoded payloads. Binary payloads are not supported.

Looking at a JSON Call

Here is an Action configured for JSON and the resulting execution. The use of POST and sending the customer ID in the message body is due to the design of the service. I would also add a content-type to the call, just to be sure.

Conclusion

As long as you do not have the need to send data in binary to a backend service, you should really start using this connector and not bother with the custom connector.