Appendix B. Fabric URL Handlers

Abstract

The Fabric runtime provides a variety of URL handlers, which can be used in application code deployed in a Fabric-enabled container. These URLs are intended to be used in profile configuration files to locate configuration resources.

B.1. Profile URL handler

The profile URL is used to access resources stored under the current profile (or parent profile). It has the following format:
profile:ResourceName
A key characteristic of the profile URL is that the location of a resource can change dynamically at run time, as follows:
  1. The profile URL handler first tries to find the named resource, ResourceName, in the current version of the current profile (where the current version is a property of the container in which the profile is running).
  2. If the specified resource is not found in the current profile, the profile URL tries to find the resource in the current version of the parent profile.
This behavior implies that whenever you change the version assigned to a container (for example, by invoking the fabric:container-upgrade or fabric:container-rollback console commands), the referenced resources are also, automatically, upgraded or rolled back.
Profile URL handler service reference for bundles
You need to define a profile URL handler service reference for a bundle to avoid the race condition. If the service reference is not defined the bundle attempts to use the profile protocol before it is actually available for usage. An example to define the service reference in the blueprint.xml file is as follows:
 
<reference id="resolverRef" interface="org.osgi.service.url.URLStreamHandlerService" filter="(url.handler.protocol=profile)" availability="mandatory"/> .