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JonathanM
Frequent Visitor

HTTP Post multipart/form-data

Hi,

 

I am trying to post SharePoint files to a 3rd party via their API.  Their API uses multipart/form-data.  After some trial and error, I can POSTcontent, but only text files come out correctly on the destination.  Other files (Excel, Word, jpg, etc.) post, but the data is not readable. What do I need to do to the file content to format it properly?

 

Thanks!

 

http post.png

 

38 REPLIES 38
WillPage
Impactful Individual
Impactful Individual

@davidlist87  Your file content is not base64 encoded. Where you are specifying the file content, use an expression like base64(body('whatever')?['File_Content']) where whatever is the name of the action where you got that file content from dropbox.

 

Write base64() in the expression builder, click between the brackets then switch to the dynamic content tab and find the File Content.

@WillPage thanks for your help but it seams to be throwing an input error.

My expression is: base64(body('When a file is modified')?['triggerBody()'])

Feel like we are really close...

Image 5.jpg

WillPage
Impactful Individual
Impactful Individual

You need to use Get File Content as an additional step. After your trigger, add the Dropbox Get File Content action, and use its output in your HTTP POST.

@WillPage I was able to get the base64 conversion to work but am still getting the same error.

Thanks very much for your help mate👍

Image 7.jpg

 

WillPage
Impactful Individual
Impactful Individual

The two properties of the body should be $content and $content-type. You've omitted the dollar signs.

I took the time to document this here: https://willpagenz.wordpress.com/2019/12/20/using-the-http-action-to-post-multipart-form-data-in-pow...

@WillPage you are a legend! Thank you so much to your contribution on this subject. Not a lot a info around about and you were all over it 👍

Image 10.jpg

Amazing! It works perfectly. So glad you posted solution, I've been trying to work it out for months 😀

Hi did u guys solve this ? i have a similair problem.  Thats my postman setup, need this into power automate. Its demanding a multipart/form-data, and a jpg url 

postman.png

Yes, it is solved and works. You cannot use the Postman code. Check how the solution is written. You need to be extremely careful to keep the json correctly formatted and re-write your field names as needed.

what shall be in the headers ? Content-type : multipart/form-data ? 

Hm getting connection, but image its not uploaded. I know the server demands multipart/form-data and jpeg 

this its my input 

{"uri":"https://login.glaskontroll.se/apitest/filesubmit.php","method":"POST","headers":{"Content-Type":"multipart/form-data"},"body":{"$content-type":"multipart/form-data","$multipart":[{"headers":{"Content-Disposition":"form-data; name=\"Username\""},"body":"test"},{"headers":{"Content-Disposition":"form-data; name=\"Password\""},"body":"pw"},{"headers":{"Content-Disposition":"form-data; name=\"Carregno\""},"body":"LJ0000"},{"headers":{"Content-Disposition":"form-data; name=\"Type\""},"body":"damage"},{"headers":{"Content-Disposition":"form-data; name=\"file\"; filename=\"navn.jpg\""},"body":{"$content-type":"application/jpg","$content":"base64url 

Not sure what is the output of your base64url...but in a previous action try getting file content (save file first to OneDrive for Business) and then put a base64() expression around your file content. Your expression will look like this:

base64(outputs('Get_file_content')?['body'])

 

Made it work, only thing its that i store the images in a collection from power apps, and some of the images its getting a "," before the base64url and causes a conflict 

WillPage
Impactful Individual
Impactful Individual

You could trim off any leading comma in a compose using a formula like this (warning, phone typing!):

 

If(equals(substring({url},0,1),','),substring({url},1,sub(length({url}),1)),{url})

 

Where {url} is the dynamic content that contains the string. What this does is look at the first character, and if it equals a comma then trim the first character off, else return the whole string.

thanks it worked. One thing i am struggling with its that i think the power apps never executed the flow... The flow works if i test in power automate but when i test in power apps i dont see any response on the web server 

Make sure you have set the button / trigger correctly in PowerApps. See documentation below:

https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/using-logic-flows

 

If you have made changes in the Flow it may have broken the connection in PowerApps. To fix you remove the connection in PowerApps and then add it again (essentially refresh the connection). 

 

A good habit when doing this update is before reconnecting copy your existing PowerApp connection code somewhere. Once you update you lose any custom codes, variables etc that you wrote.

Found the issue it still inserts "," before the base64 😕

@WillPage 

@SamPo 

 

Awesome work you guys have done here! 👍

cindyc
Frequent Visitor

Guys, thanks so much for all the great work!  It helped me immensely! I wanted to share what I was trying to accomplish and some of the things that you guys showed that got it working, just in case my scenario is similar to someone elses;

 

In MS FLOW, The built-in HTTP action is a "PREMIUM" action. I'm trying not to have the company Im helping spend anymore than they already are on MS TEAMS etc, so I can't/won't use any premium actions.

 

What I'm trying to do is come up with a free way to make a REST API call to my computer (that has a public hostname setup on one of my machines) so that when I send a PDF file over the API, I can have Flask/Python convert it into a text file, and send parsed out fields back to MS FLOW in json format.

 

It looks like Custom Connectors is the way to go.  But I ran into some problems.  Everything worked perfectly on Postman, the multipart/form-data was picked up from the request inside the request.files dict in flask, and I was able to (test save to make sure it was not corrupt) work on the file PDF no sweat. But when I tried to export the Postman collection in v1 export, it would not work.  I tried exporting the Postman v2 file and converting it to Swagger/OpenApi 2.0 json file, and while the conversion worked fine, getting the multipart/form-data piece to put the file inside request.files did not work, no matter what I tried.  But then I found this thread and things started to come together. After alot of fruitless testing from the Custom Connector Swagger Editor (it kept putting an @ in front of the filename for some reason, but I copied the CURL command and ran it from cmd, still to no avail), and then trying "Import from sample" in the Custom Connector Definition screen, nothing seemed to work, although a few times the filename did appear in requests.form dict in flask, but the data was not there. I tried putting the "$content-type": "multipart/form-data" string inside the header, and that didn't work either.  I did Use the MS FLOW HTTP action for a bit though, cuz I think you get a 30 day trial. Here is what I put in the HTTP action body section, with no header info, just to see if it would work;

 

cindyc_0-1612573646318.png

 

It worked just like the guys here said it would, multipart/form-data worked just like Postman did, and Flask/Python picked the file up in request.files and I was able to save the pdf file no prob. What worked for me to make sure the pdf file was not corrupted once it got to Flask/Python was to use;

 

base64(outputs('Get_file_content')?['body'])

 

I tried a few iterations like base64(outputs('Get_file_content')) <-- no ['body'], but the above was the one that worked.

 

But my custom connector was still having problems. Here is what finally worked in the "Import from sample" section, just like the guys here said it would;

 

cindyc_7-1612576459856.png

 

 

I just blurred out the filename above in the pic a little bit, but if you do it this way uploading a file via a MS FLOW Custom Connector will work.  Now here is one thing that stumped me; the Custom Connector "Test" screen. 

 

cindyc_2-1612574665070.png

 

I tested via this thing many, many times, and although the REST API call was made, the multipart/form-data was not properly formatted in the request object, meaning the pdf file was never in either request.files or request.form, or in the json object inside the request. But I decided to plug this Custom Connector inside the Flow I was working on, just to see if maybe it would be different, and possibly be properly formatted in the request object. And sure enough it was! Here is a look at the Flask/Python debugger with the pdf file inside request.files;

 

cindyc_9-1612577035392.png

 

What this shows is that the pdf 'file' is inside the requests.files dict and the multipart/form-data is properly formatted inside the REST API function. 

 

One other thing that got me right before it started working was how I was putting in the variables in the Connector once I put it into my Flow. In the Content-Disposition field I entered the information just like I did when I built the Custom Connector using "form-data; name=\"file\"; filename=\"20210129172849290.pdf\"".

But when it gets to the API, it will add a bunch of extra uneeded characters.  I decided not to use the text editor fields to put the data inside the Connector, I just use the fields/text boxes provided by the Custom Connector which works fine. So I removed the slashes and double quotes, and now here is what the Custom Connector looks like inside my flow with everything working (just blurred the filename a little);

 

cindyc_8-1612576638749.png

 

 

Thank you so much for all the help, I was pulling my hair out for a long while, could not have done it without you!,

Thanks,

EC

 

 

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