ASA 17.0.10: Question about calling external web services and passing binary data to them

[Stalker4]

Hi,

There is some external web service. I need to call it and pass binary data to it.
For this purpose I have created my own procedure:

CREATE PROCEDURE "dba"."WebTest2Run"( in "data" long binary,in "cAccessToken" long varchar,in "nCustomerID" integer,in "filename" char(20) ) 
result( "cAttribute" long varchar,"cValue" long varchar,"npp" integer ) 
url 'http://OtherSite/WebTest1'
type 'HTTP:POST:application/pdf'
header 'Authorization: !cAccessToken; \x0AContent-Disposition: form-data; name="nCustomerID" !nCustomerID; \x0AContent-Disposition: form-data; name="files"; filename="!filename"'

I call it like this:

 select * from dba.WebTest2Run(MyBinaryData, 'MyToken', 47, 'test.pdf')
 where cAttribute = 'Body'

 I need "Content-Disposition" to be specified twice in the header.

Content-Disposition: form-data; name="nCustomerID" 47 
Content-Disposition: form-data; name="files"; filename="test.pdf" 

But for some reason the second "Content-Disposition" setting overrides the first one, i.e. only the second setting remains in the header:

Content-Disposition = form-data; name="files"; filename="test.pdf"

 Is there any way to fix this ?

And another question: When calling an external web service and passing binary data to it, is it possible to make http-header as in the picture below ?

In particular I am interested in the "boundary" and "muiltipart" parts of the http header ?

[VolkerBarth]

Are you sure HTTP allows for multiple "Content-Disposition" headers? AFAIK multiple headers with the same name are primarily allowed for "Set-Cookie" headers. - I don't know whether you can add the values comma-separated in one single header line.

In my understanding of the docs, listing a header field name within the HEADER clause does modify the previous field with the same name, so the second "Content-Disposition" entry overwrites the first, so the behaviour you are noticing seems expected.

[Stalker4]

You Can.

Specification Reference. 

[VolkerBarth]

I'm no HTTP expert, but I guess the Content-Disposition in your sample is NOT part of the HTTP header but the HTTP body (as there's the empty line above that follows the HTTP header), so you might just have to add it to the body you provide?

[Stalker4]

If you mean the example in the first image, you may be right, but considering that I need to pass binary data to this service, I don't understand how I should form an HTTP body with "boundary", "Content-Disposition" and "multipart". Maybe you can make such an example ?

[PCollins · Accepted solution]

You need to do multipart for multiple Content-Dispositions and put them within the body parts, you can do it like this:

url 'api.endpoint.com'
set 'HTTP(EXCEPTIONS=off; VERSION=1.1)'
type 'HTTPS:POST:multipart/form-data'
header 'Connection:keep-alive \x0AAccept: */* \x0AContent-Type: multipart/form-data; boundary=XXXXboundary'

Then in your body you will need to list each of the boundaries for each part such as  

'--XXXXboundary\x0D\x0AContent-Disposition: form-data; name="@"; filename="' || @fileName || '"\x0D\x0A\x0D\x0A' || replace(replace(@csvData,',0,',',0.01,'),',.',',0.') || '\x0D\x0A--XXXXboundary--'

Hope this gets you going in the right direction.

[Stalker4 · Accepted solution]

Where do the numbers next to "boundary" come from ?

[PCollins · Accepted solution]

you can use whatever you want for the boundary string, see https://www.w3.org/Protocols/rfc1341/7_2_Multipart.html

[Stalker4 · Accepted solution]

I understand correctly that I will have to recode binary data into BASE64 (Function BASE64_ENCODE) ? P.S. I honestly thought that if you pass long binary data to a web function (in my example WebTest2Run), the recoding will be done automatically, as well as adding the necessary parts of the request header and body. But judging by your answer I was wrong.

[PCollins · Accepted solution]

This is how I have got it working, ultimately however you do it, in whatever language, you will need the client to conform, I guess you might have just use languages that have libraries available where someone else has done all this as reusable code?

Personally I like have full control over the raw transmission.   

You will need to use whatever encoding the endpoint is expecting, it isn't always BASE64. 
You can read more about encoding here: https://www.w3.org/Protocols/rfc1341/5_Content-Transfer-Encoding.html

But yes if you haven't stored the data in your tables BASE64 encoded and they want BASE64 encoded you will need to use BASE64_ENCODE()