org.eclipse.ajdt.cuprovider/plugin.xml

<?xml version="1.0" encoding="UTF-8"?>
<?eclipse version="3.0"?>
<plugin>

   <!-- use experimental ICompilationUnitProvider extension point -->
   <extension point="org.eclipse.jdt.core.compilationUnitProvider">
     <compilationUnitProvider file-extensions="aj"
       class="org.eclipse.ajdt.cuprovider.AspectJCompilationUnitProvider"/>
   </extension>
</plugin>