为什么我不能在SecurityManager下关闭自己的ExecutorService？
在默认的安全管理器下，如果我创建了一个ExecutorService（在这种情况下是ThreadPoolExecutor），我就无法将其关闭，
shutdown()
checkPermission("modifyThread")import java.util.concurrent.*;
class A {
public static void main( String[] args) {
Thread ct = Thread.currentThread();
System.out.println("current thread: " + ct);
ct.checkAccess(); // we have access to our own thread...
ThreadPoolExecutor tpe = new ThreadPoolExecutor(
1, // one core thread
1, // doesn't matter because queue is unbounded
0, TimeUnit.SECONDS, // doesn't matter in this case
new LinkedBlockingQueue<Runnable>(), /* unbound queue for
* our single thread */
new ThreadFactory() {
public Thread newThread(Runnable r) {
// obviously never gets called as we don't add any work
System.out.println("making thread");
return new Thread(r);
}
}
);
tpe.shutdown(); // raises security exception
}
}
shutdown
SecurityException
/**
* Initiates an orderly shutdown in which previously submitted
* tasks are executed, but no new tasks will be accepted.
* Invocation has no additional effect if already shut down.
*
* @throws SecurityException {@inheritDoc}
*/
public void shutdown() {
final ReentrantLock mainLock = this.mainLock;
mainLock.lock();
try {
checkShutdownAccess();
advanceRunState(SHUTDOWN);
interruptIdleWorkers();
onShutdown(); // hook for ScheduledThreadPoolExecutor
} finally {
mainLock.unlock();
}
tryTerminate();
}
/**
* If there is a security manager, makes sure caller has
* permission to shut down threads in general (see shutdownPerm).
* If this passes, additionally makes sure the caller is allowed
* to interrupt each worker thread. This might not be true even if
* first check passed, if the SecurityManager treats some threads
* specially.
*/
private void checkShutdownAccess() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkPermission(shutdownPerm);
final ReentrantLock mainLock = this.mainLock;
mainLock.lock();
try {
for (Worker w : workers)
security.checkAccess(w.thread);
} finally {
mainLock.unlock();
}
}
}
checkPermission(shutdownPerm)
modifyThread
ThreadFactory
SecurityException
shutdownNow
没有找到相关结果
已邀请:
2 个回复
bab
。 要回答这个问题：只需确保您授予自己的代码权限，您就会感到高兴。或者“modifyThread”也可以自由授予，它主要由applet使用。 至于不受信任的代码：嗯，不受信任的代码甚至不应该处理其ThreadGroup之外的线程，因此提供API来创建ThreadPool，并允许关闭由调用者创建的。您可以根据呼叫者授予权限。 希望这有点帮助（问号的数量清楚地表明了绝望和最大的烦恼）/* * Conceptually, shutdown is just a matter of changing the * runState to SHUTDOWN, and then interrupting any worker * threads that might be blocked in getTask() to wake them up * so they can exit. Then, if there happen not to be any * threads or tasks, we can directly terminate pool via * tryTerminate. Else, the last worker to leave the building * turns off the lights (in workerDone). * * But this is made more delicate because we must cooperate * with the security manager (if present), which may implement * policies that make more sense for operations on Threads * than they do for ThreadPools. This requires 3 steps: * * 1. Making sure caller has permission to shut down threads * in general (see shutdownPerm). * * 2. If (1) passes, making sure the caller is allowed to * modify each of our threads. This might not be true even if * first check passed, if the SecurityManager treats some * threads specially. If this check passes, then we can try * to set runState. * * 3. If both (1) and (2) pass, dealing with inconsistent * security managers that allow checkAccess but then throw a * SecurityException when interrupt() is invoked. In this * third case, because we have already set runState, we can * only try to back out from the shutdown as cleanly as * possible. Some workers may have been killed but we remain * in non-shutdown state (which may entail tryTerminate from * workerDone starting a new worker to maintain liveness.) */漂汀拦