Download a Document from s3 using webservice call

RE: Download a Document from s3 using webservice call

nathan.schmitz — Tue, 25 Apr 2017 13:01:19 GMT

If fetching the entire document is the only feasible approach, you probably need to build a plugin that will contain an expression or activity that downloads the document into Appian and returns the Appian document.

RE: Download a Document from s3 using webservice call

Ben Edwards — Mon, 24 Apr 2017 20:07:32 GMT

Very interesting, thanks for the info. Obviously I haven't tried this myself but might be worth looking into at some point. I know a lot of the functionality used by servlets can be replicated via Web APIs but perhaps as you've noted this it proves to be too limiting for this use case.

RE: Download a Document from s3 using webservice call

rawich — Mon, 24 Apr 2017 19:58:46 GMT

@bene, it may be possible, but there are many challenges with using Web API for this requirement.

There is a Shared Component "Amazon S3 Utilities" available as Smart Service plug-in. With that, you can download a file from Amazon S3 into Appian document.
Challenge #1 - You have to call the Smart Service by starting a new process, but you won't know when the the file is ready, and you can't wait either.

If you got through that hurdle, you can try to extract Appian document download URL from a deprecated function linktodocument(), then redirect the browser to download the document. But yes, it's deprecated, so this solution will only be temporary.

There is also a concern about cleaning up, after the file is downloaded.

I can imagine a quick and dirty proof-of-concept can be implemented using Web API, but not as a production ready solution.

forum.appian.com/.../Scripting_Functions.html

RE: Download a Document from s3 using webservice call

Ben Edwards — Mon, 24 Apr 2017 16:33:57 GMT

Seems like you could use a Web API for it then too?

RE: Download a Document from s3 using webservice call

rawich — Mon, 24 Apr 2017 16:17:19 GMT

I accomplished similar requirement using Servlet plug-in.

From Appian UI, you can create a link to the Servlet with document unique identifier in the URI (as query parameter). When the user clicked on the link to the Servlet, your Java code do all these works in one go: call S3 service to download the file into temporary directory, determine file type to set the correct content type of the file, send the file content to the browser, delete the temporary file.

There are a few gotchas along the way, but your Java developers should be able to handle them. Let me know if you want to go this route, and have further questions.

RE: Download a Document from s3 using webservice call

Ben Edwards — Mon, 24 Apr 2017 15:51:24 GMT

This seems like an interesting issue. I'm not sure at this point that there's a way to correlate users with access to S3 to users within Appian to help bridge the gap between the two? I don't think a new S3 bucket policy would do the trick without some custom development on the Appian side either.

RE: Download a Document from s3 using webservice call

Shreehari Gopalakrishnan Ramanan — Mon, 24 Apr 2017 15:24:30 GMT

You are correct . But our architecture team is limiting the direct access to S3.

RE: Download a Document from s3 using webservice call

nathan.schmitz — Fri, 21 Apr 2017 13:29:23 GMT

Is there a reason why you can't simply construct or fetch a link to the document in S3 and display the link to the user so that they can download the document?