Extending the DAV server

Nextcloud apps can extend the DAV server by registering SabreDAV plugins that hook into different phases of a DAV request. Plugins can add handlers for custom methods and properties, adjust response behavior, and more. See Writing Plugins - sabre/dav for additional possibilities.

Registering a DAV plugin

To register a server plugin in your app, register an event listener for OCA\DAV\Events\SabrePluginAddEvent (introduced in Nextcloud 28). In the listener’s handler, add your DAV plugin to the server.

For example:

MyApplication.php

class MyApplication extends App implements IBootstrap {
    public function register(IRegistrationContext $context): void {
        $context->registerEventListener(SabrePluginAddEvent::class, MyListener::class);
    }
}

MyListener.php

use OCP\EventDispatcher\Event;
use OCP\EventDispatcher\IEventListener;
use OCA\DAV\Events\SabrePluginAddEvent;

class MyListener implements IEventListener {
    public function handle(Event $event): void {
        if (!$event instanceof SabrePluginAddEvent) {
            return;
        }
        $server = $event->getServer();
        $server->addPlugin(new MyDavPlugin());
    }
}

Handling DAV events

In this example, we register a handler for the propFind event and add a custom property that is returned in PROPFIND requests.

MyDavPlugin.php

use Sabre\DAV\ServerPlugin;
use Sabre\DAV\PropFind;

class MyDavPlugin extends ServerPlugin {

    public function initialize(\Sabre\DAV\Server $server): void {
        // Register your property handler
        $server->on('propFind', $this->handleGetProperties(...));
    }

    private function handleGetProperties(PropFind $propFind, \Sabre\DAV\INode $node): void {
        // Add a property called "my-property" with the value "custom"
        $propFind->handle('{myapplication.example}my-property', fn() => 'custom');
    }
}

Performance considerations

In the example above, if you replace the “custom” value with a database lookup, you introduce a performance issue: a query runs every time the property is loaded. This may not be obvious at first, but it quickly becomes a problem, because a propFind event is emitted for every file in a collection to discover its properties. If a collection contains 1,000 children, the code issues 1,000 queries that are likely very similar, differing only by the file identifier.

To mitigate this, Nextcloud 32 introduces a new event that signals your app to preload data for a collection and its immediate children. Read more in WebDAV collection preload events.