使用XQL / exist-db将文档上传到服务器

Question

APP Structure

NiC
| upload.xq
| upload.html
| controller.xql
| assignments.html (a lot of files are in the main dir, which is probably not good)
| templates/page.html
| inReview/
| data/all the xml files currently in the database
| images/all the images currently in the db
| modules/app.xql
| modules/view.xql

Not all the files are here, but just some that are relevant and to give a flavor.

New discovery and problem as it now stands

I have been trying to get this uploader to work, and I've been stymied at every turn--BUT, I think it is finally working. However, it works in a very weird way, and I don't know why. Not knowing why it works this way and not another way is driving me crazy, and it will cause other problems down the line. So, I'm hoping someone can shed some light!

I'm basically hacking together something new from pieces of the sample Shakespeare archive in eXist-db. So, the structure of my whole app is virtually the same as the ship-with demo. That having been said:

in page.html, which templates the whole look of the page and provides the header/navigation information:

I have added a link to the navigation that goes to an upload page:

<li><a href="../upload.html">Contribute</a></li>

upload.html:

<div xmlns="http://www.w3.org/1999/xhtml" class="templates:surround?with=templates/page.html&amp;at=main">
        <form enctype="multipart/form-data" method="post" action="upload.xql">
            <fieldset>
            <legend>Upload an XML File for Review:</legend>
            <input type="file" name="file"/>
            <button id="f-btn-upload" name="f-btn-upload" value="true" type="submit" class="btn btn-danger">Upload</button>
        </fieldset>
    </form>
</div>

upload.xql:

xquery version "3.0";

let $collection := '/db/apps/NiC/inReview/'
let $filename := request:get-uploaded-file-name('file')

(: make sure you use the right user permissions that has write access to this collection :)
let $login := xmldb:login($collection, 'username', 'superstrongpassword')
let $store := xmldb:store($collection, $filename, request:get-uploaded-file-data('file'))


return
<results>
   <message>File {$filename} has been stored at collection={$collection}.</message>
</results>

All of this works, somehow. But the weird thing is in the controller.xql:

Here's the relevant bit:

else if ($exist:resource = ("search.html", "form1.html", "demo-queries.html", "search-help.html", "about-NiC.html", "assignments.html", "success.html", "upload.html")) then
    (: the html page is run through view.xql to expand templates :)
    (: question: 11/2017 why if upload.html is noted here does the URL need to be relative to ../upload.html from page.html, though others don't? :)
    <dispatch xmlns="http://exist.sourceforge.net/NS/exist">
        <forward url="{$exist:controller}/{$exist:resource}">
            <set-header name="Cache-Control" value="no-cache"/>
        </forward>
        <view>
            <forward url="{$exist:controller}/modules/view.xql"/>
        </view>
        <error-handler>
            <forward url="{$exist:controller}/error-page.html" method="get"/>
            <forward url="{$exist:controller}/modules/view.xql"/>
        </error-handler>
    </dispatch>

If in page.html I use just the link "upload.html" as the controller would seem to require (upload.html is in the same place and doing the same kind of thing in general that the other pages are, like assignments.html and so on) it doesn't work. I get the SAX exception error/content not allowed in prolog. The other pages are accessible, and the URL resolution is working as expected. But if the link is "../upload.html," the page is accessible and the upload works as I want it to.

So my question is this: why? Why can't I just use upload.html as the path, trusting the controller to do what it does? Why do I have to gerrymander a solution with the relative path?

Argh!

Answer 1

The return type of request:get-uploaded-file-data() is xs:base64Binary* while xmldb:store() expects "either a node, an xs:string, a Java file object or an xs:anyURI" (from the function documentation). So you have to pipe the result through util:binary-to-string() first like

xmldb:store($collection, $filename, util:binary-to-string(request:get-uploaded-file-data('file')))

The error you see is because xmldb:store() throws an XPathException if unsuccessful.

Answer 2

So just to clarify your app structure is?

yourapp
| modules/upload.xq
| templates/page.html
| upload.html
| other1.html
| controller.xql

Do your other1.html files also call .xq modules? The controller handles .html and .xq files differently, so to go from modules/upload.xq you need to use a relative path step ../ to reach upload.html.

That being said, you are not alone in often being dumbfunded by the templating system's opinion on where things are at the moment :)