how to send payload as multipart/form to request in mule4 - multipartform-data

Question

i transform a payload need to send as as multipart/form to request.
the payload is like below
{
"goods_id": "12345,
"color_id_1": 20,
"image_id_1": vars.png1, //this is binary ,image data
"color_id_2": 11,
"image_id_2": vars.png1, //this is binary ,image data
}
here is sample file which we need to transform, the file is base on postman script.
in postman we can choose image file from notebook. in payload, the image is an object
which is stored in variable .
POST /cooperate/RegistAllImage HTTP/1.1
Content-Type: multipart/form-data; boundary=--------------------------549967118512544277394909
User-Agent: PostmanRuntime/7.29.0
Accept: */*
Cache-Control: no-cache
Postman-Token: ddddd
Host: ddddd
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Cookie: *****
Content-Length: 40980
----------------------------549967118512544277394909
Content-Disposition: form-data; name="goods_id"
Content-Type: application/x-www-form-urlencoded
12345
----------------------------549967118512544277394909
Content-Disposition: form-data; name="color_id_1"
Content-Type: application/x-www-form-urlencoded
20
----------------------------549967118512544277394909
Content-Disposition: form-data; name="image_1"; filename="064df7cefee0421990ccb74a5c1f9ccf.jpg"
Content-Type: application/octet-stream
<064df7cefee0421990ccb74a5c1f9ccf.jpg>
----------------------------549967118512544277394909
Content-Disposition: form-data; name="color_id_2"
Content-Type: application/x-www-form-urlencoded
2
----------------------------549967118512544277394909
Content-Disposition: form-data; name="image_2"; filename="064df7cefee0421990ccb74a5c1f9ccf.jpg"
Content-Type: application/octet-stream
<064df7cefee0421990ccb74a5c1f9ccf.jpg>

Answer 1

You can very well use the Multipart form module or can construct the parts using the script below.
%dw 2.0
import dw::module::Multipart
output multipart/form-data boundary="--------------------------549967118512544277394909"
---
{
parts: {
part1: Multipart::field({
name: "goods_id",
value: payload.goods_id,
mime: "appliation/x-www-form-urlencoded"
}),
part2: Multipart::field({
name: "color_id_1",
value: payload.color_id_1,
mime: "appliation/x-www-form-urlencoded"
})
,
part3: Multipart::field({
name: "image_id_1",
value: payload.image_id_1,
mime: "appliation/octet-stream",
fileName: "064df7cefee0421990ccb74a5c1f9ccf.jpg"
})
,
part4: Multipart::field({
name: "color_id_2",
value: payload.color_id_2,
mime: "appliation/x-www-form-urlencoded"
})
,
part5: Multipart::field({
name: "image_id_2",
value: payload.image_id_2,
mime: "appliation/octet-stream",
fileName: "064df7cefee0421990ccb74a5c1f9ccf.jpg"
})
}
}
Answer to the question in comment:
%dw 2.0
import dw::module::Multipart
output multipart/form-data boundary="--------------------------549967118512544277394909"
---
{
parts: payload mapObject ((value, key, index) -> {
("part" ++ ((index)+1)): Multipart::field({
"name": key as String,
"value": value as String,
"mime": if(key startsWith "image_id_") "application/octet-stream" else "application/x-www-form-urlencoded",
("fileName": "filenmae.png" )if(key startsWith "image_id_")
})
})
}

Answer 2

you can use the Multipart dataweave module that will make it fairly simple.
You will need Multipart::form function to create the form, and pass an array of all the fields, that you have in your payload. I have used pluck for it and then mapped it using Multipart:field function to get an Array of type MultipartPart. Your transform module will look like this
%dw 2.0
import dw::module::Multipart
output multipart/form-data
---
Multipart::form(
payload pluck ((value, key) ->
if(key as String startsWith "image_id_")
Multipart::field(key as String, value, "application/octet-stream")
else Multipart::field( key as String, value as String)
)
)