CustomConnector etag parameter

[jiwanovski]

Hi everbody,

I cam creating a custom connector to connect with a partner solution of Microsoft Dynamics Business Central.

Business Central provie some API features which is the base for the custom connector.

Scenario:

- Types of Request: GET, POST and PATCH

- GET and POST Request are working fine on every part: Postman, CustomConnector Test Area and PowerApps

- PATCH Request is only working with POSTMAN and Custom Connector Test Area. On PowerApps I always get the information, that another user has already changed the record. 

Detail information on Patch:

- To send the PATCH Request I need to send the information / node "etag" with the request

- The "etag" information is placed within the header and the key "If-Match"

Screenshot of the parameter setup for "If-Match" on CustomConnector

Currently I assume that this setup may cause this error because of Type = string. 

Has anybody else worked with API, PATCH Request and "If-Match" yet?

[Anonymous]

Hi jiwanovski,

You are almost there.

The etag is a dynamic feature of a record, it says which "version" of the record you want to modify.

if the current version of bc and your version are a match than the modification is allowed.

so what you want to do is:

-http (get) the latest E-tag of the record you want to modify 

- http(Patch) the just received e-tag in the if-Match.

This way BC accepts your change because your change is based on the latest "version"

[jiwanovski]

Hi @Anonymous 

thank you for your quick response. 

Aktually I do this already, but I still get the message, that some User has changed the dataset before. 

What I am doing:

- First I get a set of records of a table with a GetRequest

- This is assigned as Item for a gallery

- In gallery I have some controls to modify single fields and an icon to save

- With the OnSelect of the icon I try to do the PATCH. Here I just reference to the ThisItem.'@odata.etag' to give the etag information....

But I still get the error message "Another user has changed the record"....

Any idea what I should test?

Which version of BC have you tested (which client build?)

[Anonymous · Accepted solution]

in base, all version of BC work in general.

The message you get is purely from a wrong inputted etag.

check in your get comment if the @odata.etag is Type:string Format: ""

Same for the if-Match parameter Type: string Format: ""

Also do you patch the same entity as where the get is from?

Etags are page related, so if you get from a different page then to which you patch you also may experience the error

[v-xida-msft]

Hi @jiwanovski ,

Have you taken a try to remove the "W/" prefix from the ETag value (default value) you set for the If-Match header in your Patch request?

Please consider take a try to remove the  "W/" prefix from the ETag value (default value) you set for the If-Match header in your Patch request, then try your custom connector again, check if the issue is solved.

In addition, the ETag value of the "If-Match" header is required to provide a string of ASCII characters rather than a HTML text. Please check the following article for more details:

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag

Please consider set Format property to Blank as below:

Please take a try with above solution, then check if the issue is solved.

Best regards,

[jiwanovski]

Hi everbody,

I agree that this should be a format problem of the etag value. 

For the GET and the PATCH request I use the same API Page. So I have believed that I just can take the value from GET response. 

I also modified the etag parameter to String blank (GET and PATCH) again. This was the value by default (I just changed this in case of testing purpose). 

I also tried to eleminate the removing the prefix "w/" value and set this to header with "If-Match" or just do put the "@odata.etag" direct into the Body.... Nothing helped... 

What I wonder if there is anything on the value of the GET response itself wrong?

This is how it looks like in Postman

"@odata.etag": "W/\"JzQ0O1c1a1JkaDE3RW80QUxsR3FkVm0rNGZOUDJSekNSN0VXdkI0RlpyN0NWNXM9MTswMDsn\""

I also tried to just remove the "\" in this string...

Any other ideas?

[jiwanovski]

Hi everybody,

@Anonymous and I just had a short call on that and he was already right before.

When I tried to send the PATCH Request, I hadn't the correct etag value in place.

How it is not working:

(1) Get a list of records (including a etag value) with somethink like: https://yourURL.com/BC130/api/V1/API/beta/companies/:companyId/APIEntity?$filter=ID eq dbeb2692-1fa6-490d-9f54-147a3e422a5e

(2) Add this to a gallery

(3) Add Buttion to do the PATCH Request

(4) In OnSelect calling PATCH Request like: https://yourURL.com/BC130/api/V1/API/beta/companies/:companyId/APIEntity/:entityID

If you do it like this way, you will get always that another user has changed the record.

Before you do Step (4) you have to do a single API Request like: https://yourURL.com/BC130/api/V1/API/beta/companies/:companyId/APIEntity/:entityID

So even both GET Request are based on the same Page in BC I first have to do the GET statement for the single record and take the etag value from there. Then it is running.

So many thanks to @Anonymous!!!!

The solved answer should get to you! 

[MadW]

Hi @jiwanovski 

How did you create your body of the patch call.

When patching we only need to send updated field data like

{"itemName": "New Itemname"}, 

But in a scenario where PowerApp user might change 1 or more out of 10 possible fields, I would like to supply my updated field(s) name and field(s) value(s).

Thanks