how to display a JFrame from an applet?

Question

I have this class called PollFrame that extends JFrame in a file called PollFrame.java . PollFrame contains a form. I have an applet, which has a button in it. When the button is clicked, I want the PollFrame to be displayed. I set the ActionPerformed as:

Pollframe poll = new PollFrame(); // This initializes the form
poll.setVisible(true);

However, when I click the button, I get the following error :

Exception in thread "AWT-EventQueue-2" java.security.AccessControlException: access denied (java.lang.RuntimePermission exitVM.0)
    at java.security.AccessControlContext.checkPermission(Unknown Source)
    at java.security.AccessController.checkPermission(Unknown Source)
    at java.lang.SecurityManager.checkPermission(Unknown Source)
    at java.lang.SecurityManager.checkExit(Unknown Source)
    at javax.swing.JFrame.setDefaultCloseOperation(Unknown Source)
    at com.org.pollFrame.initComponents(pollFrame.java:54)
    at com.org.pollFrame.<init>(pollFrame.java:11)
    at com.org.EmployeeApplet.requestRoomActionPerformed(EmployeeApplet.java:216)
    at com.org.EmployeeApplet.access$300(EmployeeApplet.java:7)
    at com.org.EmployeeApplet$4.actionPerformed(EmployeeApplet.java:71)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

I am guessing fromt he above error that calling another class file from an applet is prohibited. Is there any way I can display the PollFrame from the applet?

Answer 1

It seems like you're calling setDefaultCloseOperation() on your JFrame, which raises the security exception

You can definitively call another class from an applet but some operations are restricted, eg. you can't open local files, open connections to other machines...

Answer 2

I have this class called PollFrame that extends JFrame in a file called PollFrame.java . PollFrame contains a form. I have an applet, which has a button in it. When the button is clicked, I want the PollFrame to be displayed.

This is a one liner:

applet.showDocument("PollFrame.jnlp", "_blank");

The frame launched by PollFrame.jnlp will be able to call any default close operation it likes while still sand-boxed, since it will have a separate VM. To be 'always on top' it will need to be trusted (and then fight it out with all the other apps. that aim to be always on top).