retter | simple server that provides circuit | Runtime Evironment library

This answer, which covers only basic URL rewriting, assumes that the eXist application is built using what I'll call "basic" eXist app architecture:

• The app, which we'll call "my-app", is stored in /db/apps/my-app.
• No modifications have been made to the Jetty configuration files in EXIST_HOME/tools/jetty/etc, the XQuery servlet configuration file in EXIST_HOME/webapp/WEB-INF/web.xml, or the base configuration for eXist's URL rewriting at webapp/WEB-INF/controller-config.xml.
• This means the application can be accessed at http://localhost:8080/exist/apps/my-app. (If the goal is to serve this application via a URL like http://my-server/ and have this routed to eXist at http://localhost:8080/exist/apps/my-app, this is best handled by a reverse proxy server, which is beyond the scope of "basic" eXist app architecture.)
• We will handle URL rewriting via eXist's URL rewriting facility - i.e., writing a controller.xql file - rather than via RESTXQ.

With these assumptions, we can create completely custom URLs, allowing us to take a URL like:

• http://localhost:8080/exist/apps/my-app/doc.xq?filename=my-document.xml

and make this same resource available via:

• http://localhost:8080/exist/apps/my-app/doc/my-document

To accomplish this, we need to create a new XQuery main module, named controller.xql (it must be called this exactly, and we'll call it the app's "controller") in the root collection of your app: /db/apps/my-app/controller.xql. This is a special module, which eXist looks for first when a request comes for a path in the /apps URL space (e.g., http://localhost:8080/exist/apps/...). While typically an app will have only one controller, eXist supports multiple controllers; eXist looks in the target collection and then up the collection tree, from deepest branch up to the root /db/apps collection.

The purpose of the controller is to take information about the request - the path requested and other information about the app's context - and return a special kind of directive, which tells eXist how to route the request. The key information about the request is exposed to your query in a series of external variables (variables you don't have to define that eXist sets for you and that you can reference), including, most importantly, $exist:path - the portion of the request URL that comes after the path to the collection containing the controller. So in the URL above, $exist:path would equal /doc/my-document.

Now, let's create the directive that takes this path and forwards this request (formulated using with the filename parameter to your actual endpoint: