There is a small problem with the exolab xdoclet module. We will have it fixed in the next patch release very soon.
However, if you can’t wait for our fix, you can do it locally:
1) go to the folder: $MYECLIPSE_INSTALLDIR/eclipse/plugins/com.genuitec.jboss.ide.eclipse.xdoclet.core_3.8.0/
2) Extract the xdoclet-exolab-module-1.2.jar to a temp folder
3) Open the META-INF/xtags.xml
4) Edit line 7 to contain: <name>castor</name>
5) Rejar the contents of the module, make a backup of the current copy and place new jar file in xdoclet.core plugin.
6) Go to preference page MyEclipse->XDoclet->Code Assist and click on “Refresh XDoclet Data”
Then your castor mapping should work correctly.