custom submenu won't react on click - oracle-sqldeveloper

Question

I am trying to implement an extension in JDeveloper. It creats a submenu when you click on a DB package.
THe issue comes when I click on an element of my custom submenu, it returns a null pointer Exception.
I can't figure out where I did wrong.
Would you please help me?
Here is how a I created the submenu:
submenu.xml File:
<?xml version="1.0" encoding="windows-1252" ?>
<!-- usage of a name space?-->
<items id="my.contextMenu">
<folder type="PACKAGE">
<name>User Defined Context Menu</name>
<item reloadparent="true"
action-ref="utilitytools.customSave">
<title>saveThisPackage</title>
</folder>
</items>
extension.xml file:
<?xml version="1.0" encoding="UTF-8" ?>
<extension id="utilitytools" version="1.0" esdk-version="1.0"
rsbundle-class="utilitytools.Res"
xmlns="http://jcp.org/jsr/198/extension-manifest">
<name>Utility Tools</name>
<owner>A name</owner>
<dependencies>
<import>oracle.sqldeveloper</import>
<import>oracle.ide</import>
</dependencies>
<hooks>
<jdeveloper-hook xmlns="http://xmlns.oracle.com/jdeveloper/1013/extension">
<addins>
<addin>utilitytools.UtilityToolsAddin</addin>
</addins>
<actions xmlns="http://xmlns.oracle.com/jdeveloper/1013/extension">
<action id="utilitytools.customSave">
<properties>
<property name="Name">saveThisPackage</property>
<property name="SmallIcon"></property>
<property name="LongDescription"></property>
</properties>
<controller-class>utilitytools.savePackageController</controller-class>
<command-class>utilitytools.savePackageCommand</command-class>
</action>
</actions>
</jdeveloper-hook>
<sqldev-navigator-hook xmlns="http://xmlns.oracle.com/sqldeveloper/sqldev-navigator">
<descriptor>submenu.xml</descriptor>
</sqldev-navigator-hook>
</hooks>
</extension>
SubmenuListener file:
public final class SubMenuListener implements ContextMenuListener {
public SubMenuListener() {
super();
}
public void menuWillShow(ContextMenu contextMenu) {
contextMenu.add( contextMenu.createMenuItem(
IdeAction.find( savePackageCommand.actionId() )
));
}
public void menuWillHide(ContextMenu contextMenu) {
//Nothing
}
public boolean handleDefaultAction(Context context) {
return false;
}
}
And the command file:
/**
* Command handler for utilitytools.customSave.
*/
#RegisteredByExtension("utilitytools")
public final class sauvegardePackageCommand extends Command {
public savePackageCommand() {
super(actionId());
}
public int doit() {
SwingUtilities.invokeLater(new Runnable(){
public void run(){
showSaveWindow();
}
});
return OK;
}
/**
* Returns the id of the action this command is associated with.
*
* #return the id of the action this command is associated with.
* #throws IllegalStateException if the action this command is associated
* with is not registered.
*/
public static int actionId() {
final Integer cmdId = Ide.findCmdID(".utilitytools.customSave");
if (cmdId == null)
throw new IllegalStateException("Action esdksample.showElementClass not found.");
return cmdId;
}
private static void showSaveWindow(){
JFrame frame = new JFrame("SAVE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JPanelSavePackage());//Or any window you want to popup
frame.pack();
frame.setVisible(true);
}
}