HTTP engines


XP applications using the XP framework are essentially powered by the runtime’s HTTP engine. The HTTP engine is responsible for handling web-based request to the runtime.


By default, the XP runtime serves HTTP requests from port 8080 (customizable). There are three specific web engine implementations available:

Each engine provides a purpose specific request processing and execution pipeline.

Common request pipeline

All HTTP engines share a common request pipeline as specified below:

Common HTTP request pipeline
Vhost filters

Request routing based on virtual hosts

Java request filters

Optional Java request filters

Auth filter

The virtual host contextual ID provider will be invoked, unless a user already exists in the context

Engine pipeline

If nothing else matches, the pipeline of the specific engine will be executed

Asset service

Serves static assets for the /_/asset/* request patterns

HTTP Service

Provide access to Http service controllers through the /_/service/* request pattern

IDprovider Service

For direct interaction with the contextual IDprovider based on the /_/idprovider/* request patterns

Auth handler

Triggered if the pipeline returns a "401: Unauthorized" error code, the contextual IDprovider will be invoked, optionally handling the request

Error handler

If the pipeline returns an unhandled error (everything but "200: Ok") that was not handled by an ID provider, the contextual error handler will kick in.

Java response filters

Optional Java response filters

Standard error handler

Finally, if the request fails with an error that is still unhandled, XP’s standard error handler will kick in

Underscore endpoint

All engines reserve the use of the underscore characther _ (by itself) to provide engine specific endpoints. This applies to at any location within the URL path hierarchy. For instance, the following request :8080/webapp/<webapp>/_/ or :8080/site/<project>/<branch>/some/content/_/ are reserved.