Bug 21183 Class javadoc created during "New Class" operation doesn't fill in variables properly [javadoc] [code manipulation]
If you use the enclosing_type variable in your javadoc comment template, it is not properly filled in when you make a new class (using the New Class dialog). Probably the class should be created, then after creating and saving, javadoc should be added. I suspect the variables don't have valid values yet at the time the javadoc is prepended to the class.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/javadoc/JavaDocAutoIndentStrategy.java
int[] caretOffset= {c.offset};
			jdocWrapParagraphFromLine(document, document.getLineOfOffset(c.offset), caretOffset, always);
			c.offset= caretOffset[0];
		} catch (BadLocationException e) {
			JavaPlugin.log(e);
		}
	}
	/**
	 * Returns the compilation unit of the CompilationUnitEditor invoking the AutoIndentStrategy,
	 * might return <code>null</code> on error.
	 */
	private static ICompilationUnit getCompilationUnit() {
		IWorkbenchWindow window= PlatformUI.getWorkbench().getActiveWorkbenchWindow();
		if (window == null)
			return null;
			
		IWorkbenchPage page= window.getActivePage();
		if (page == null)	
			return null;
		IEditorPart editor= page.getActiveEditor();
		if (editor == null)
			return null;
		IWorkingCopyManager manager= JavaPlugin.getDefault().getWorkingCopyManager();
		ICompilationUnit unit= manager.getWorkingCopy(editor.getEditorInput());
		if (unit == null)
			return null;
		return unit;
	}
			
}