Extending SCR Annotations Excerpt: How add new Annotations extending the base Annotations
|This page documents functionality available with the SCR Generator 1.0.0 release providing the declaration file generation mechanism for the Maven SCR Plugin 1.6.0 (and newer) and the SCR Ant Task 1.0.0 (and newer).|
The SCR Annotations library has been updated in version 1.4.0 to comply with the rules described here. As such this library may be used as basis to learn more about providing pluggbale Java 5 annotations for the Maven SCR Plugin and SCR Ant Task. The source code for the SCR Annotations library is available from the Apache Felix SVN repository at annotations.
This page outlines the required steps to implement your own extended Java 5 annotations:
Define the Annotations
It is interesting to note, that the SCR Annotations 1.4.0 library providing the default and Sling Java 5 tags for the SCR Generator by itself is already implemented according to the rules outlined herein. This means, that actually the SCR Generator does not have any built-in annotations but only provides the framework to allow for the definition of Java 5 Annotations.
To start with you will define Java 5 Annotations to suit your application needs.
org.apache.felix.scr.annotations.sling package provides three sample annotations:
SlingServlet— used to declare a
javax.servlet.Servletservice component with the appropriate service registration properties to configure the service as an Apache Sling Servlet.
SlingFilter— used to declare a
javax.servlet.Filterservice component with the appropriate service registration properties to configure the service as a Filter used by the Apache Sling Main Servlet.
SlingFilterScope— helper annotation to define the
filter.scopeservice registration property for Filters defined with the
These annotations will be used to annotate classes for use with Declarative Services.
It is suggested to maintain the annotations in a separate package or even in a separate module that your projects may depend upon.
AnnotationProcessor interface defines the interface of a helper class which is used to convert Java 5 Annotation data into internal data structures to be then used as the basis for the generation of the descriptor files.
SlingAnnotationProcessor class implements the
AnnotationProcessorto handle the Sling annotations described above.
To finally make the
AnnotationProcessor implementations available to the SCR Generator (and thus the Maven SCR Plugin and/or SCR Ant Task) the fully qualified class names of these implementations must be listed in an
META-INF/services/org.apache.felix.scrplugin.annotations.AnnotationProcessor file in the library providing the annotations.
The classes listed in this file will automatically be picked up by the SCR Generator from the library placed on the build class path and thus enable support for the respective annotations.
Again, refer to the actual implementation in the SCR Annotations library referred to above.