The AppContext.java Java example source code
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package sun.awt;
import java.awt.EventQueue;
import java.awt.Window;
import java.awt.SystemTray;
import java.awt.TrayIcon;
import java.awt.Toolkit;
import java.awt.GraphicsEnvironment;
import java.awt.event.InvocationEvent;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Collections;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.Set;
import java.util.HashSet;
import java.beans.PropertyChangeSupport;
import java.beans.PropertyChangeListener;
import sun.util.logging.PlatformLogger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.atomic.AtomicInteger;
/**
* 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.<p>
*
* 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.<p>
*
* For example, here we have a Foo service, with its pre-AppContext
* code:<p>
* <code>
* public class Foo {
* private static Foo defaultFoo = new Foo();
*
* public static Foo getDefaultFoo() {
* return defaultFoo;
* }
*
* ... Foo service methods
* }</pre>
*
* 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.<p>
*
* Here's the Foo class written to use the AppContext:<p>
* <code>
* 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
* }</pre>
*
* 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.<p>
*
* 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
*/
public final class AppContext {
private static final PlatformLogger log = PlatformLogger.getLogger("sun.awt.AppContext");
/* Since the contents of an AppContext are unique to each Java
* session, this class should never be serialized. */
/*
* The key to put()/get() the Java EventQueue into/from the AppContext.
*/
public static final Object EVENT_QUEUE_KEY = new StringBuffer("EventQueue");
/*
* The keys to store EventQueue push/pop lock and condition.
*/
public final static Object EVENT_QUEUE_LOCK_KEY = new StringBuilder("EventQueue.Lock");
public final static Object EVENT_QUEUE_COND_KEY = new StringBuilder("EventQueue.Condition");
/* A map of AppContexts, referenced by ThreadGroup.
*/
private static final Map<ThreadGroup, AppContext> threadGroup2appContext =
Collections.synchronizedMap(new IdentityHashMap<ThreadGroup, AppContext>());
/**
* Returns a set containing all <code>AppContexts.
*/
public static Set<AppContext> getAppContexts() {
synchronized (threadGroup2appContext) {
return new HashSet<AppContext>(threadGroup2appContext.values());
}
}
/* The main "system" AppContext, used by everything not otherwise
contained in another AppContext. It is implicitly created for
standalone apps only (i.e. not applets)
*/
private static volatile AppContext mainAppContext = null;
private static class GetAppContextLock {};
private final static Object getAppContextLock = new GetAppContextLock();
/*
* The hash map associated with this AppContext. A private delegate
* is used instead of subclassing HashMap so as to avoid all of
* HashMap's potentially risky methods, such as clear(), elements(),
* putAll(), etc.
*/
private final Map<Object, Object> table = new HashMap<>();
private final ThreadGroup threadGroup;
/**
* If any <code>PropertyChangeListeners have been registered,
* the <code>changeSupport field describes them.
*
* @see #addPropertyChangeListener
* @see #removePropertyChangeListener
* @see #firePropertyChange
*/
private PropertyChangeSupport changeSupport = null;
public static final String DISPOSED_PROPERTY_NAME = "disposed";
public static final String GUI_DISPOSED = "guidisposed";
private enum State {
VALID,
BEING_DISPOSED,
DISPOSED
};
private volatile State state = State.VALID;
public boolean isDisposed() {
return state == State.DISPOSED;
}
/*
* The total number of AppContexts, system-wide. This number is
* incremented at the beginning of the constructor, and decremented
* at the end of dispose(). getAppContext() checks to see if this
* number is 1. If so, it returns the sole AppContext without
* checking Thread.currentThread().
*/
private static final AtomicInteger numAppContexts = new AtomicInteger(0);
/*
* The context ClassLoader that was used to create this AppContext.
*/
private final ClassLoader contextClassLoader;
/**
* Constructor for AppContext. This method is <i>not public,
* nor should it ever be used as such. The proper way to construct
* an AppContext is through the use of SunToolkit.createNewAppContext.
* A ThreadGroup is created for the new AppContext, a Thread is
* created within that ThreadGroup, and that Thread calls
* SunToolkit.createNewAppContext before calling anything else.
* That creates both the new AppContext and its EventQueue.
*
* @param threadGroup The ThreadGroup for the new AppContext
* @see sun.awt.SunToolkit
* @since 1.2
*/
AppContext(ThreadGroup threadGroup) {
numAppContexts.incrementAndGet();
this.threadGroup = threadGroup;
threadGroup2appContext.put(threadGroup, this);
this.contextClassLoader =
AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
public ClassLoader run() {
return Thread.currentThread().getContextClassLoader();
}
});
// Initialize push/pop lock and its condition to be used by all the
// EventQueues within this AppContext
Lock eventQueuePushPopLock = new ReentrantLock();
put(EVENT_QUEUE_LOCK_KEY, eventQueuePushPopLock);
Condition eventQueuePushPopCond = eventQueuePushPopLock.newCondition();
put(EVENT_QUEUE_COND_KEY, eventQueuePushPopCond);
}
private static final ThreadLocal<AppContext> threadAppContext =
new ThreadLocal<AppContext>();
private final static void initMainAppContext() {
// On the main Thread, we get the ThreadGroup, make a corresponding
// AppContext, and instantiate the Java EventQueue. This way, legacy
// code is unaffected by the move to multiple AppContext ability.
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
ThreadGroup currentThreadGroup =
Thread.currentThread().getThreadGroup();
ThreadGroup parentThreadGroup = currentThreadGroup.getParent();
while (parentThreadGroup != null) {
// Find the root ThreadGroup to construct our main AppContext
currentThreadGroup = parentThreadGroup;
parentThreadGroup = currentThreadGroup.getParent();
}
mainAppContext = SunToolkit.createNewAppContext(currentThreadGroup);
return null;
}
});
}
/**
* Returns the appropriate AppContext for the caller,
* as determined by its ThreadGroup. If the main "system" AppContext
* would be returned and there's an AWTSecurityManager installed, it
* is called to get the proper AppContext based on the execution
* context.
*
* @return the AppContext for the caller.
* @see java.lang.ThreadGroup
* @since 1.2
*/
public final static AppContext getAppContext() {
// we are standalone app, return the main app context
if (numAppContexts.get() == 1 && mainAppContext != null) {
return mainAppContext;
}
AppContext appContext = threadAppContext.get();
if (null == appContext) {
appContext = AccessController.doPrivileged(new PrivilegedAction<AppContext>()
{
public AppContext run() {
// Get the current ThreadGroup, and look for it and its
// parents in the hash from ThreadGroup to AppContext --
// it should be found, because we use createNewContext()
// when new AppContext objects are created.
ThreadGroup currentThreadGroup = Thread.currentThread().getThreadGroup();
ThreadGroup threadGroup = currentThreadGroup;
// Special case: we implicitly create the main app context
// if no contexts have been created yet. This covers standalone apps
// and excludes applets because by the time applet starts
// a number of contexts have already been created by the plugin.
synchronized (getAppContextLock) {
if (numAppContexts.get() == 0) {
if (System.getProperty("javaplugin.version") == null &&
System.getProperty("javawebstart.version") == null) {
initMainAppContext();
} else if (System.getProperty("javafx.version") != null &&
threadGroup.getParent() != null) {
// Swing inside JavaFX case
SunToolkit.createNewAppContext();
}
}
}
AppContext context = threadGroup2appContext.get(threadGroup);
while (context == null) {
threadGroup = threadGroup.getParent();
if (threadGroup == null) {
return null;
}
context = threadGroup2appContext.get(threadGroup);
}
// In case we did anything in the above while loop, we add
// all the intermediate ThreadGroups to threadGroup2appContext
// so we won't spin again.
for (ThreadGroup tg = currentThreadGroup; tg != threadGroup; tg = tg.getParent()) {
threadGroup2appContext.put(tg, context);
}
// Now we're done, so we cache the latest key/value pair.
threadAppContext.set(context);
return context;
}
});
}
return appContext;
}
/**
* Returns true if the specified AppContext is the main AppContext.
*
* @param ctx the context to compare with the main context
* @return true if the specified AppContext is the main AppContext.
* @since 1.8
*/
public final static boolean isMainContext(AppContext ctx) {
return (ctx != null && ctx == mainAppContext);
}
private final static AppContext getExecutionAppContext() {
SecurityManager securityManager = System.getSecurityManager();
if ((securityManager != null) &&
(securityManager instanceof AWTSecurityManager))
{
AWTSecurityManager awtSecMgr = (AWTSecurityManager) securityManager;
AppContext secAppContext = awtSecMgr.getAppContext();
return secAppContext; // Return what we're told
}
return null;
}
private long DISPOSAL_TIMEOUT = 5000; // Default to 5-second timeout
// for disposal of all Frames
// (we wait for this time twice,
// once for dispose(), and once
// to clear the EventQueue).
private long THREAD_INTERRUPT_TIMEOUT = 1000;
// Default to 1-second timeout for all
// interrupted Threads to exit, and another
// 1 second for all stopped Threads to die.
/**
* Disposes of this AppContext, all of its top-level Frames, and
* all Threads and ThreadGroups contained within it.
*
* This method must be called from a Thread which is not contained
* within this AppContext.
*
* @exception IllegalThreadStateException if the current thread is
* contained within this AppContext
* @since 1.2
*/
public void dispose() throws IllegalThreadStateException {
// Check to be sure that the current Thread isn't in this AppContext
if (this.threadGroup.parentOf(Thread.currentThread().getThreadGroup())) {
throw new IllegalThreadStateException(
"Current Thread is contained within AppContext to be disposed."
);
}
synchronized(this) {
if (this.state != State.VALID) {
return; // If already disposed or being disposed, bail.
}
this.state = State.BEING_DISPOSED;
}
final PropertyChangeSupport changeSupport = this.changeSupport;
if (changeSupport != null) {
changeSupport.firePropertyChange(DISPOSED_PROPERTY_NAME, false, true);
}
// First, we post an InvocationEvent to be run on the
// EventDispatchThread which disposes of all top-level Frames and TrayIcons
final Object notificationLock = new Object();
Runnable runnable = new Runnable() {
public void run() {
Window[] windowsToDispose = Window.getOwnerlessWindows();
for (Window w : windowsToDispose) {
try {
w.dispose();
} catch (Throwable t) {
log.finer("exception occurred while disposing app context", t);
}
}
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
if (!GraphicsEnvironment.isHeadless() && SystemTray.isSupported())
{
SystemTray systemTray = SystemTray.getSystemTray();
TrayIcon[] trayIconsToDispose = systemTray.getTrayIcons();
for (TrayIcon ti : trayIconsToDispose) {
systemTray.remove(ti);
}
}
return null;
}
});
// Alert PropertyChangeListeners that the GUI has been disposed.
if (changeSupport != null) {
changeSupport.firePropertyChange(GUI_DISPOSED, false, true);
}
synchronized(notificationLock) {
notificationLock.notifyAll(); // Notify caller that we're done
}
}
};
synchronized(notificationLock) {
SunToolkit.postEvent(this,
new InvocationEvent(Toolkit.getDefaultToolkit(), runnable));
try {
notificationLock.wait(DISPOSAL_TIMEOUT);
} catch (InterruptedException e) { }
}
// Next, we post another InvocationEvent to the end of the
// EventQueue. When it's executed, we know we've executed all
// events in the queue.
runnable = new Runnable() { public void run() {
synchronized(notificationLock) {
notificationLock.notifyAll(); // Notify caller that we're done
}
} };
synchronized(notificationLock) {
SunToolkit.postEvent(this,
new InvocationEvent(Toolkit.getDefaultToolkit(), runnable));
try {
notificationLock.wait(DISPOSAL_TIMEOUT);
} catch (InterruptedException e) { }
}
// We are done with posting events, so change the state to disposed
synchronized(this) {
this.state = State.DISPOSED;
}
// Next, we interrupt all Threads in the ThreadGroup
this.threadGroup.interrupt();
// Note, the EventDispatchThread we've interrupted may dump an
// InterruptedException to the console here. This needs to be
// fixed in the EventDispatchThread, not here.
// Next, we sleep 10ms at a time, waiting for all of the active
// Threads in the ThreadGroup to exit.
long startTime = System.currentTimeMillis();
long endTime = startTime + THREAD_INTERRUPT_TIMEOUT;
while ((this.threadGroup.activeCount() > 0) &&
(System.currentTimeMillis() < endTime)) {
try {
Thread.sleep(10);
} catch (InterruptedException e) { }
}
// Then, we stop any remaining Threads
this.threadGroup.stop();
// Next, we sleep 10ms at a time, waiting for all of the active
// Threads in the ThreadGroup to die.
startTime = System.currentTimeMillis();
endTime = startTime + THREAD_INTERRUPT_TIMEOUT;
while ((this.threadGroup.activeCount() > 0) &&
(System.currentTimeMillis() < endTime)) {
try {
Thread.sleep(10);
} catch (InterruptedException e) { }
}
// Next, we remove this and all subThreadGroups from threadGroup2appContext
int numSubGroups = this.threadGroup.activeGroupCount();
if (numSubGroups > 0) {
ThreadGroup [] subGroups = new ThreadGroup[numSubGroups];
numSubGroups = this.threadGroup.enumerate(subGroups);
for (int subGroup = 0; subGroup < numSubGroups; subGroup++) {
threadGroup2appContext.remove(subGroups[subGroup]);
}
}
threadGroup2appContext.remove(this.threadGroup);
threadAppContext.set(null);
// Finally, we destroy the ThreadGroup entirely.
try {
this.threadGroup.destroy();
} catch (IllegalThreadStateException e) {
// Fired if not all the Threads died, ignore it and proceed
}
synchronized (table) {
this.table.clear(); // Clear out the Hashtable to ease garbage collection
}
numAppContexts.decrementAndGet();
mostRecentKeyValue = null;
}
static final class PostShutdownEventRunnable implements Runnable {
private final AppContext appContext;
public PostShutdownEventRunnable(AppContext ac) {
appContext = ac;
}
public void run() {
final EventQueue eq = (EventQueue)appContext.get(EVENT_QUEUE_KEY);
if (eq != null) {
eq.postEvent(AWTAutoShutdown.getShutdownEvent());
}
}
}
static final class CreateThreadAction implements PrivilegedAction<Thread> {
private final AppContext appContext;
private final Runnable runnable;
public CreateThreadAction(AppContext ac, Runnable r) {
appContext = ac;
runnable = r;
}
public Thread run() {
Thread t = new Thread(appContext.getThreadGroup(), runnable);
t.setContextClassLoader(appContext.getContextClassLoader());
t.setPriority(Thread.NORM_PRIORITY + 1);
t.setDaemon(true);
return t;
}
}
static void stopEventDispatchThreads() {
for (AppContext appContext: getAppContexts()) {
if (appContext.isDisposed()) {
continue;
}
Runnable r = new PostShutdownEventRunnable(appContext);
// For security reasons EventQueue.postEvent should only be called
// on a thread that belongs to the corresponding thread group.
if (appContext != AppContext.getAppContext()) {
// Create a thread that belongs to the thread group associated
// with the AppContext and invokes EventQueue.postEvent.
PrivilegedAction<Thread> action = new CreateThreadAction(appContext, r);
Thread thread = AccessController.doPrivileged(action);
thread.start();
} else {
r.run();
}
}
}
private MostRecentKeyValue mostRecentKeyValue = null;
private MostRecentKeyValue shadowMostRecentKeyValue = null;
/**
* Returns the value to which the specified key is mapped in this context.
*
* @param key a key in the AppContext.
* @return the value to which the key is mapped in this AppContext;
* <code>null if the key is not mapped to any value.
* @see #put(Object, Object)
* @since 1.2
*/
public Object get(Object key) {
/*
* The most recent reference should be updated inside a synchronized
* block to avoid a race when put() and get() are executed in
* parallel on different threads.
*/
synchronized (table) {
// Note: this most recent key/value caching is thread-hot.
// A simple test using SwingSet found that 72% of lookups
// were matched using the most recent key/value. By instantiating
// a simple MostRecentKeyValue object on cache misses, the
// cache hits can be processed without synchronization.
MostRecentKeyValue recent = mostRecentKeyValue;
if ((recent != null) && (recent.key == key)) {
return recent.value;
}
Object value = table.get(key);
if(mostRecentKeyValue == null) {
mostRecentKeyValue = new MostRecentKeyValue(key, value);
shadowMostRecentKeyValue = new MostRecentKeyValue(key, value);
} else {
MostRecentKeyValue auxKeyValue = mostRecentKeyValue;
shadowMostRecentKeyValue.setPair(key, value);
mostRecentKeyValue = shadowMostRecentKeyValue;
shadowMostRecentKeyValue = auxKeyValue;
}
return value;
}
}
/**
* Maps the specified <code>key to the specified
* <code>value in this AppContext. Neither the key nor the
* value can be <code>null.
* <p>
* The value can be retrieved by calling the <code>get method
* with a key that is equal to the original key.
*
* @param key the AppContext key.
* @param value the value.
* @return the previous value of the specified key in this
* AppContext, or <code>null if it did not have one.
* @exception NullPointerException if the key or value is
* <code>null.
* @see #get(Object)
* @since 1.2
*/
public Object put(Object key, Object value) {
synchronized (table) {
MostRecentKeyValue recent = mostRecentKeyValue;
if ((recent != null) && (recent.key == key))
recent.value = value;
return table.put(key, value);
}
}
/**
* Removes the key (and its corresponding value) from this
* AppContext. This method does nothing if the key is not in the
* AppContext.
*
* @param key the key that needs to be removed.
* @return the value to which the key had been mapped in this AppContext,
* or <code>null if the key did not have a mapping.
* @since 1.2
*/
public Object remove(Object key) {
synchronized (table) {
MostRecentKeyValue recent = mostRecentKeyValue;
if ((recent != null) && (recent.key == key))
recent.value = null;
return table.remove(key);
}
}
/**
* Returns the root ThreadGroup for all Threads contained within
* this AppContext.
* @since 1.2
*/
public ThreadGroup getThreadGroup() {
return threadGroup;
}
/**
* Returns the context ClassLoader that was used to create this
* AppContext.
*
* @see java.lang.Thread#getContextClassLoader
*/
public ClassLoader getContextClassLoader() {
return contextClassLoader;
}
/**
* Returns a string representation of this AppContext.
* @since 1.2
*/
@Override
public String toString() {
return getClass().getName() + "[threadGroup=" + threadGroup.getName() + "]";
}
/**
* Returns an array of all the property change listeners
* registered on this component.
*
* @return all of this component's <code>PropertyChangeListeners
* or an empty array if no property change
* listeners are currently registered
*
* @see #addPropertyChangeListener
* @see #removePropertyChangeListener
* @see #getPropertyChangeListeners(java.lang.String)
* @see java.beans.PropertyChangeSupport#getPropertyChangeListeners
* @since 1.4
*/
public synchronized PropertyChangeListener[] getPropertyChangeListeners() {
if (changeSupport == null) {
return new PropertyChangeListener[0];
}
return changeSupport.getPropertyChangeListeners();
}
/**
* Adds a PropertyChangeListener to the listener list for a specific
* property. The specified property may be one of the following:
* <ul>
* <li>if this AppContext is disposed ("disposed")
* </ul>
* <ul>
* <li>if this AppContext's unowned Windows have been disposed
* ("guidisposed"). Code to cleanup after the GUI is disposed
* (such as LookAndFeel.uninitialize()) should execute in response to
* this property being fired. Notifications for the "guidisposed"
* property are sent on the event dispatch thread.</li>
* </ul>
* <p>
* If listener is null, no exception is thrown and no action is performed.
*
* @param propertyName one of the property names listed above
* @param listener the PropertyChangeListener to be added
*
* @see #removePropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
* @see #getPropertyChangeListeners(java.lang.String)
* @see #addPropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
*/
public synchronized void addPropertyChangeListener(
String propertyName,
PropertyChangeListener listener) {
if (listener == null) {
return;
}
if (changeSupport == null) {
changeSupport = new PropertyChangeSupport(this);
}
changeSupport.addPropertyChangeListener(propertyName, listener);
}
/**
* Removes a PropertyChangeListener from the listener list for a specific
* property. This method should be used to remove PropertyChangeListeners
* that were registered for a specific bound property.
* <p>
* If listener is null, no exception is thrown and no action is performed.
*
* @param propertyName a valid property name
* @param listener the PropertyChangeListener to be removed
*
* @see #addPropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
* @see #getPropertyChangeListeners(java.lang.String)
* @see #removePropertyChangeListener(java.beans.PropertyChangeListener)
*/
public synchronized void removePropertyChangeListener(
String propertyName,
PropertyChangeListener listener) {
if (listener == null || changeSupport == null) {
return;
}
changeSupport.removePropertyChangeListener(propertyName, listener);
}
/**
* Returns an array of all the listeners which have been associated
* with the named property.
*
* @return all of the <code>PropertyChangeListeners associated with
* the named property or an empty array if no listeners have
* been added
*
* @see #addPropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
* @see #removePropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)
* @see #getPropertyChangeListeners
* @since 1.4
*/
public synchronized PropertyChangeListener[] getPropertyChangeListeners(
String propertyName) {
if (changeSupport == null) {
return new PropertyChangeListener[0];
}
return changeSupport.getPropertyChangeListeners(propertyName);
}
// Set up JavaAWTAccess in SharedSecrets
static {
sun.misc.SharedSecrets.setJavaAWTAccess(new sun.misc.JavaAWTAccess() {
private boolean hasRootThreadGroup(final AppContext ecx) {
return AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
@Override
public Boolean run() {
return ecx.threadGroup.getParent() == null;
}
});
}
/**
* Returns the AppContext used for applet logging isolation, or null if
* the default global context can be used.
* If there's no applet, or if the caller is a stand alone application,
* or running in the main app context, returns null.
* Otherwise, returns the AppContext of the calling applet.
* @return null if the global default context can be used,
* an AppContext otherwise.
**/
public Object getAppletContext() {
// There's no AppContext: return null.
// No need to call getAppContext() if numAppContext == 0:
// it means that no AppContext has been created yet, and
// we don't want to trigger the creation of a main app
// context since we don't need it.
if (numAppContexts.get() == 0) return null;
// Get the context from the security manager
AppContext ecx = getExecutionAppContext();
// Not sure we really need to re-check numAppContexts here.
// If all applets have gone away then we could have a
// numAppContexts coming back to 0. So we recheck
// it here because we don't want to trigger the
// creation of a main AppContext in that case.
// This is probably not 100% MT-safe but should reduce
// the window of opportunity in which that issue could
// happen.
if (numAppContexts.get() > 0) {
// Defaults to thread group caching.
// This is probably not required as we only really need
// isolation in a deployed applet environment, in which
// case ecx will not be null when we reach here
// However it helps emulate the deployed environment,
// in tests for instance.
ecx = ecx != null ? ecx : getAppContext();
}
// getAppletContext() may be called when initializing the main
// app context - in which case mainAppContext will still be
// null. To work around this issue we simply use
// AppContext.threadGroup.getParent() == null instead, since
// mainAppContext is the only AppContext which should have
// the root TG as its thread group.
// See: JDK-8023258
final boolean isMainAppContext = ecx == null
|| mainAppContext == ecx
|| mainAppContext == null && hasRootThreadGroup(ecx);
return isMainAppContext ? null : ecx;
}
});
}
}
final class MostRecentKeyValue {
Object key;
Object value;
MostRecentKeyValue(Object k, Object v) {
key = k;
value = v;
}
void setPair(Object k, Object v) {
key = k;
value = v;
}
}
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