What is the Actions folder in the system filesystem, and why should I use it?

When you use @ActionRegistration the META-INF/generated-layer.xml may contain:

<folder name="Actions">
   <folder name="Build">
     <file name="com-foo-SomeAction.instance"/>
   </folder>
</folder>
<folder name="Menu">
   <folder name="Build">
     <file name="pointerToComFooSomeAction.shadow">
        <attr name="originalFile" stringvalue="Actions/Build/com-foo-SomeAction.instance"/>
     </file>
   </folder>
</folder>

And you may have noticed that actions are usually put, not directly into the Menu/ folders, but into subfolders of this Actions/ folder. Then we create .shadow files that act like symbolic links, pointing to the real .instance file . Why all this indirection?

Older versions of the NetBeans UI included the ability to rearrange, and even delete, whole menus or individual menu items, and future ones may again. (Many applications built on NetBeans will not want to expose such customizability, but some do.) The current UI does include a key binding editor; the Actions/ folder can be used from this editor to list available actions, even those which are not currently bound to any keystroke.

Additionally, for actions which are javax.swing.Action but not SystemAction, creating the action instance in only a single place ensures that it acts as a singleton. (While the action class likely has no declared instance fields, it does have some state, notably information about keyboard accelerators which should be displayed in menu presenters.)

Applies to: NetBeans 6.7 and above

Apache NetBeans 24

What is the Actions folder in the system filesystem, and why should I use it?