A handler conflict occurred. This may disable some commands

Question

I want to be able to control when a particular command can be enabled in a toolbar. Currently this is in my plugin.xml file:

<extension
     point="org.eclipse.ui.commands">
  <command
        defaultHandler="my.plugin.handler.Terminate"
        description="Terminate session"
        id="my.plugin.terminate"
        name="Terminate">
  </command>
</extension>
<extension
     point="org.eclipse.ui.commandImages">
  <image
        commandId="my.plugin.terminate"
        icon="icons/terminate.gif">
  </image>
</extension>
  <extension point="org.eclipse.ui.menus">
  <menuContribution locationURI="toolbar:my.plugin.views.RuntimeSessionsView">
     <command
           commandId="my.plugin.terminate"
           disabledIcon="icons/terminate_dis.gif"
           icon="icons/terminate.gif"
           style="push">
     </command>
</menuContribution>
</extension>
<extension
     point="org.eclipse.ui.handlers">
  <handler
        class="my.plugin.handler.Terminate"
        commandId="my.plugin.terminate">
     <enabledWhen>
        <with
              variable="canTerminate">
           <equals
                 value="true">
           </equals>
        </with>
     </enabledWhen>
  </handler>
</extension>

And here is what I get in the console:

!ENTRY org.eclipse.ui.workbench 2 0 2015-03-11 11:59:05.237
!MESSAGE A handler conflict occurred.  This may disable some commands.
!SUBENTRY 1 org.eclipse.ui.workbench 2 0 2015-03-11 11:59:05.237
!MESSAGE Conflict for 'my.plugin.terminate':
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)
WARNING 15-03-11,11:59:05 (0) Conflict for 'my.plugin.terminate':
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)
  Conflict for 'my.plugin.terminate':
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)
HandlerActivation(commandId=my.plugin.terminate,
    handler=my.plugin.handler.Terminate,
    expression=,sourcePriority=0)

Currently the my.plugin.terminate command is disabled and I am getting this error message. It would disappear if I would deleted the last extension point ("org.eclipse.ui.handlers"), but then the my.plugin.terminate command would be enabled again.

➤ What I want to achieve is to be able to control the enabled / disabled state of this command. How can I do this?

Answer 1

You have specified the same handler in the command default handler and the handler extension point. Since they are both active you get a conflict.

Don't specify the default handler.