Convert this to a snap? How?

@mike.korcynski @Sowmya_Rayavarapu @robert_parks

Here is a solution to POST-ing a file with multiple form fields.

Our REST POST snap is a swiss-army knife, and I am less familiar with all of its options (multipart related, for example). I need to better understand the “entity” plumbing too. That said, let’s evaluate something that might work – maybe not an awesome solution, but hopefully something that does work.

We want to POST more than one thing, so let’s ignore the “single file upload” fields (4 of them). We’ll leave all the entity fields empty too.

The conceptual model is that we need to create a file for every field we want to submit. If we want to upload a file and also specify two form fields, we’ll create 3 files! Files can be referenced in SLDB, or the filesystem which may be less convenient for you depending on your Snaplex filesystem access.

Here’s the top half of the REST POST snap showing the fields I left empty.

I’ve attached two simple pipelines each with a single REST POST snap.

For the first pipeline we want to upload a file (directory.xml) and also specify two form fields. Here’s the curl version:

curl -X POST http://127.0.0.1:8001/test \
    --form "upload=@directory.xml" \
    --form "field1=field1-value" \
    --form "field2=field2-value"

We can define the form fields as files using the form field name as the “Upload-file key”. We then specify a file which contains the form field’s value. field1.txt stores the string “field1-value”. We also specify the content type as text/plain.

Here’s how the POST is received in my test server.

> POST /test

> REQUEST HEADERS:
Accept=[*/*]
Connection=[Keep-Alive]
Host=[127.0.0.1:8001]
Transfer-encoding=[chunked]
Content-type=[multipart/form-data; boundary=PusHivUIyaSW4MgQOpnzZn0wvMu-KHt2]

> REQUEST BODY:
--PusHivUIyaSW4MgQOpnzZn0wvMu-KHt2
Content-Disposition: form-data; name="upload"; filename="directory.xml"
Content-Type: application/xml; charset=UTF-8
Content-Transfer-Encoding: binary

<directory name="foo">
  <file>file1.txt</file>
  <file>file2.json</file>
</directory>

--PusHivUIyaSW4MgQOpnzZn0wvMu-KHt2
Content-Disposition: form-data; name="field1"; filename="x"
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: binary

field1-value

--PusHivUIyaSW4MgQOpnzZn0wvMu-KHt2
Content-Disposition: form-data; name="field2"; filename="x"
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: binary

field2-value

--PusHivUIyaSW4MgQOpnzZn0wvMu-KHt2--

Ok, for the second pipeline we get a bit more ambitious and double it, that is, upload 2 files, and specify 4 form fields. The second file in this case is an image (a SnapLogic logo, of course!). We also specify some of the form field files on the filesystem (ie, file:///tmp). The 4th form field is defined as json. That’s a nice part of multipart upload, each part defines its content type.

I’ve attached all the assets and pipelines for above, including the request POST output for the 2nd pipeline POST against my test server.

There may be some more clever, more elegant plumbing that others can share – please do! I was just focusing on how to get something to work for you (and me, and others).

Do let me know if this helps, or if doesn’t, where you are having problems. Many of our snaps wrap REST API’s so you don’t have to think about these details.

rest-post-1-file-2-form-fields_2021_08_13.slp (3.7 KB)
rest-post-2-files-4-form-fields_2021_08_13.slp (4.6 KB)
rest-post-example-assets.zip (7.7 KB)