Examples of sun.awt.AppContext

sun.awt.AppContext
The AppContext is a table referenced by ThreadGroup which stores application service instances. (If you are not writing an application service, or don't know what one is, please do not use this class.) The AppContext allows applet access to what would otherwise be potentially dangerous services, such as the ability to peek at EventQueues or change the look-and-feel of a Swing application.
Most application services use a singleton object to provide their services, either as a default (such as getSystemEventQueue or getDefaultToolkit) or as static methods with class data (System). The AppContext works with the former method by extending the concept of "default" to be ThreadGroup-specific. Application services lookup their singleton in the AppContext.
For example, here we have a Foo service, with its pre-AppContext code:
```
 public class Foo { private static Foo defaultFoo = new Foo(); public static Foo getDefaultFoo() { return defaultFoo; } ... Foo service methods }
```
The problem with the above is that the Foo service is global in scope, so that applets and other untrusted code can execute methods on the single, shared Foo instance. The Foo service therefore either needs to block its use by untrusted code using a SecurityManager test, or restrict its capabilities so that it doesn't matter if untrusted code executes it.
Here's the Foo class written to use the AppContext:
```
 public class Foo { public static Foo getDefaultFoo() { Foo foo = (Foo)AppContext.getAppContext().get(Foo.class); if (foo == null) { foo = new Foo(); getAppContext().put(Foo.class, foo); } return foo; } ... Foo service methods }
```
Since a separate AppContext can exist for each ThreadGroup, trusted and untrusted code have access to different Foo instances. This allows untrusted code access to "system-wide" services -- the service remains within the AppContext "sandbox". For example, say a malicious applet wants to peek all of the key events on the EventQueue to listen for passwords; if separate EventQueues are used for each ThreadGroup using AppContexts, the only key events that applet will be able to listen to are its own. A more reasonable applet request would be to change the Swing default look-and-feel; with that default stored in an AppContext, the applet's look-and-feel will change without disrupting other applets or potentially the browser itself.
Because the AppContext is a facility for safely extending application service support to applets, none of its methods may be blocked by a a SecurityManager check in a valid Java implementation. Applets may therefore safely invoke any of its methods without worry of being blocked. Note: If a SecurityManager is installed which derives from sun.awt.AWTSecurityManager, it may override the AWTSecurityManager.getAppContext() method to return the proper AppContext based on the execution context, in the case where the default ThreadGroup-based AppContext indexing would return the main "system" AppContext. For example, in an applet situation, if a system thread calls into an applet, rather than returning the main "system" AppContext (the one corresponding to the system thread), an installed AWTSecurityManager may return the applet's AppContext based on the execution context. @author Thomas Ball @author Fred Ecks


    /**
     * {@inheritDoc}
     */
    public void uninitialize() {
        AppContext context = AppContext.getAppContext();
        synchronized (BasicPopupMenuUI.MOUSE_GRABBER_KEY) {
            Object grabber = context.get(BasicPopupMenuUI.MOUSE_GRABBER_KEY);
            if (grabber != null) {
                ((BasicPopupMenuUI.MouseGrabber)grabber).uninstall();
            }
        }
        synchronized (BasicPopupMenuUI.MENU_KEYBOARD_HELPER_KEY) {
            Object helper = context.get(BasicPopupMenuUI.MENU_KEYBOARD_HELPER_KEY);
            if (helper != null) {
                ((BasicPopupMenuUI.MenuKeyboardHelper) helper).uninstall();
            }
        }


        if(invocator != null) {
            AccessController.doPrivileged(invocator);
            invocator = null;
        }


        if (disposer != null) {
            // Note that we're likely calling removePropertyChangeListener()
            // during the course of AppContext.firePropertyChange().
            // However, EventListenerAggreggate has code to safely modify
            // the list under such circumstances.
            context.removePropertyChangeListener(AppContext.GUI_DISPOSED,
                                                 disposer);
            disposer = null;
        }
    }

View Full Code Here


        private void scheduleDisplayChanges() {
            // To avoid threading problems, we notify each RepaintManager
            // on the thread it was created on.
            for (Object c : AppContext.getAppContexts()) {
                AppContext context = (AppContext) c;
                synchronized(context) {
                    if (!context.isDisposed()) {
                        EventQueue eventQueue = (EventQueue)context.get(
                            AppContext.EVENT_QUEUE_KEY);
                        if (eventQueue != null) {
                            eventQueue.postEvent(new InvocationEvent(
                                Toolkit.getDefaultToolkit(),
                                new DisplayChangedRunnable()));

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        return getKeymapTable().get(nm);
    }


    private static HashMap<String,Keymap> getKeymapTable() {
        synchronized (KEYMAP_TABLE) {
            AppContext appContext = AppContext.getAppContext();
            HashMap<String,Keymap> keymapTable = 
                (HashMap<String,Keymap>)appContext.get(KEYMAP_TABLE);
            if (keymapTable == null) {
                keymapTable = new HashMap<String,Keymap>(17);
                appContext.put(KEYMAP_TABLE, keymapTable);
                //initialize default keymap
                Keymap binding = addKeymap(DEFAULT_KEYMAP, null);
                binding.setDefaultAction(new 
                                         DefaultEditorKit.DefaultKeyTypedAction());
            }

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    // ********************************
    //          Create PLAF
    // ********************************
    public static ComponentUI createUI(JComponent c) {
        AppContext appContext = AppContext.getAppContext();
        WindowsLabelUI windowsLabelUI = 
                (WindowsLabelUI) appContext.get(WINDOWS_LABEL_UI_KEY);
        if (windowsLabelUI == null) {
            windowsLabelUI = new WindowsLabelUI();
            appContext.put(WINDOWS_LABEL_UI_KEY, windowsLabelUI);
        }
        return windowsLabelUI;
    }

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    // ********************************
    //         Create PLAF
    // ********************************
    public static ComponentUI createUI(JComponent c) {
        AppContext appContext = AppContext.getAppContext();
        MotifRadioButtonUI motifRadioButtonUI = 
                (MotifRadioButtonUI) appContext.get(MOTIF_RADIO_BUTTON_UI_KEY);
        if (motifRadioButtonUI == null) {
            motifRadioButtonUI = new MotifRadioButtonUI();
            appContext.put(MOTIF_RADIO_BUTTON_UI_KEY, motifRadioButtonUI);
        }
        return motifRadioButtonUI;
    }

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    // ********************************
    //          Create PLAF
    // ********************************
    public static ComponentUI createUI(JComponent c){
        AppContext appContext = AppContext.getAppContext();
        MotifButtonUI motifButtonUI = 
                (MotifButtonUI) appContext.get(MOTIF_BUTTON_UI_KEY);
        if (motifButtonUI == null) {
            motifButtonUI = new MotifButtonUI();
            appContext.put(MOTIF_BUTTON_UI_KEY, motifButtonUI);
        }
        return motifButtonUI;
    }

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    // ********************************
    //          Create PLAF
    // ********************************
    public static ComponentUI createUI(JComponent c){
        AppContext appContext = AppContext.getAppContext();
        WindowsButtonUI windowsButtonUI = 
                (WindowsButtonUI) appContext.get(WINDOWS_BUTTON_UI_KEY);
        if (windowsButtonUI == null) {
            windowsButtonUI = new WindowsButtonUI();
            appContext.put(WINDOWS_BUTTON_UI_KEY, windowsButtonUI);
        }
        return windowsButtonUI;
    }

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     * Called by SeaGlassLookAndFeel when the look and feel is being
     * uninstalled. Performs general cleanup of any app-context specific data.
     */
    static void uninitialize() {
        // get the appcontext that we've stored data in
        AppContext ctx = AppContext.getAppContext();


        // get the pcl stored in app context
        PropertyChangeListener pcl = (PropertyChangeListener) ctx.get("SeaGlassStyle.defaults.pcl");


        // if the pcl exists, uninstall it from the UIDefaults tables
        if (pcl != null) {
            UIManager.getDefaults().removePropertyChangeListener(pcl);
            UIManager.getLookAndFeelDefaults().removePropertyChangeListener(pcl);
        }


        // clear out the compiled defaults
        ctx.put("SeaGlassStyle.defaults", null);
    }

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        // map on each call to this method where "values" was null. It turns
        // out this was happening a lot.
        // To remove this bottleneck, we store the compiled TreeMaps of defaults
        // in the appContext for reuse. It is nulled whenever the UIDefaults
        // changes and recomputed when necessary.
        final AppContext ctx = AppContext.getAppContext();


        // fetch the defaults from the app context. If null, then create and
        // store the compiled defaults
        Map<String, TreeMap<String, Object>> compiledDefaults = (Map<String, TreeMap<String, Object>>) ctx.get("SeaGlassStyle.defaults");


        if (compiledDefaults == null) {


            // the entire UIDefaults tables are parsed and compiled into
            // this map of maps. The key of the compiledDefaults is the
            // prefix for each style, while the value is a map of
            // keys->values for that prefix.
            compiledDefaults = new HashMap<String, TreeMap<String, Object>>();


            // get all the defaults from UIManager.getDefaults() and put them
            // into the compiledDefaults
            compileDefaults(compiledDefaults, UIManager.getDefaults());


            // This second statement pulls defaults from the laf defaults
            UIDefaults lafDefaults = UIManager.getLookAndFeelDefaults();


            compileDefaults(compiledDefaults, lafDefaults);


            // if it has not already been done, add a listener to both
            // UIManager.getDefaults() and UIManager.getLookAndFeelDefaults().
            PropertyChangeListener pcl = (PropertyChangeListener) ctx.get("SeaGlassStyle.defaults.pcl");


            // if pcl is null, then it has not yet been registered with
            // the UIManager defaults for this app context
            if (pcl == null) {


                // create a PCL which will simply clear out the compiled
                // defaults from the app context, causing it to be recomputed
                // on subsequent passes
                pcl = new DefaultsListener();


                // add the PCL to both defaults tables that we pay attention
                // to, so that if the UIDefaults are updated, then the
                // precompiled defaults will be cleared from the app context
                // and recomputed on subsequent passes
                UIManager.getDefaults().addPropertyChangeListener(pcl);
                UIManager.getLookAndFeelDefaults().addPropertyChangeListener(pcl);


                // save the PCL to the app context as a marker indicating
                // that the PCL has been registered so we don't end up adding
                // more than one listener to the UIDefaults tables.
                ctx.put("SeaGlassStyle.defaults.pcl", pcl);
            }


            // store the defaults for reuse
            ctx.put("SeaGlassStyle.defaults", compiledDefaults);
        }


        TreeMap<String, Object> defaults = compiledDefaults.get(prefix);
        if (defaults == null) {
            defaults = new TreeMap<String, Object>();

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                Window parent = owner.get();
                if (parent != null) {
                    parent.removeOwnedWindow(weakThis);
                }
            }
            AppContext ac = context.get();
            if (null != ac) {
                Window.removeFromWindowList(ac, weakThis);
            }
        }

View Full Code Here

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