Package org.eclipse.aether.named.support

Class FileLockNamedLock

java.lang.Object

org.eclipse.aether.named.support.NamedLockSupport

org.eclipse.aether.named.support.FileLockNamedLock

All Implemented Interfaces:

AutoCloseable, NamedLock

public final class FileLockNamedLock
extends NamedLockSupport

Named lock that uses FileLock. An instance of this class is about ONE LOCK (one file) and is possibly used by multiple threads. Each thread (if properly coded re boxing) will try to obtain either shared or exclusive lock. As file locks are JVM-scoped (so one JVM can obtain same file lock only once), the threads share file lock and synchronize according to it. Still, as file lock obtain operation does not block (or in other words, the method that does block cannot be controlled for how long it blocks), we are "simulating" thread blocking using Retry utility. This implementation performs coordination not only on thread (JVM-local) level, but also on process level, as long as other parties are using this same "advisory" locking mechanism.

Since:

1.7.3

Field Summary

Fields

Modifier and Type	Field	Description
private final ReentrantLock	criticalRegion	Lock protecting "critical region": this is where threads are allowed to perform locking but should leave this region as quick as possible.
private final FileChannel	fileChannel	The FileChannel this instance is about.
private final AtomicReference<FileLock>	fileLockRef	The reference of FileLock, if obtained.
private static final long	LOCK_POSITION
private static final long	LOCK_SIZE
private static final long	RETRY_SLEEP_MILLIS
private final Map<Thread,Deque<Boolean>>	threadSteps	Thread -> steps stack (true = shared, false = exclusive)

Fields inherited from class org.eclipse.aether.named.support.NamedLockSupport

logger

Constructor Summary

Constructors

Constructor	Description
FileLockNamedLock(String name, FileChannel fileChannel, NamedLockFactorySupport factory)

Method Summary

Modifier and Type	Method	Description
private boolean	anyOtherThreadHasSteps()	Returns true if any other than this thread using this instance has any step recorded.
private Boolean	doLockExclusively()
protected boolean	doLockExclusively(long time, TimeUnit unit)
private Boolean	doLockShared()
protected boolean	doLockShared(long time, TimeUnit unit)
protected void	doUnlock()
private FileLock	obtainFileLock(boolean shared)	Attempts to obtain real FileLock, returns non-null value is succeeds, or null if cannot.

Methods inherited from class org.eclipse.aether.named.support.NamedLockSupport

close, diagnosticState, doClose, lockExclusively, lockShared, name, toString, unlock

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

RETRY_SLEEP_MILLIS

private static final long RETRY_SLEEP_MILLIS

See Also:

• Constant Field Values

LOCK_POSITION

private static final long LOCK_POSITION

See Also:

• Constant Field Values

LOCK_SIZE

private static final long LOCK_SIZE

See Also:

• Constant Field Values

threadSteps

private final Map<Thread,Deque<Boolean>> threadSteps

Thread -> steps stack (true = shared, false = exclusive)

fileChannel

private final FileChannel fileChannel

The FileChannel this instance is about.

fileLockRef

private final AtomicReference<FileLock> fileLockRef

The reference of FileLock, if obtained.

criticalRegion

private final ReentrantLock criticalRegion

Lock protecting "critical region": this is where threads are allowed to perform locking but should leave this region as quick as possible.

Constructor Details

FileLockNamedLock

public FileLockNamedLock(String name,
 FileChannel fileChannel,
 NamedLockFactorySupport factory)

Method Details

doLockShared

protected boolean doLockShared(long time,
 TimeUnit unit)
                        throws InterruptedException

Specified by:

doLockShared in class NamedLockSupport

Throws:

InterruptedException

doLockExclusively

protected boolean doLockExclusively(long time,
 TimeUnit unit)
                             throws InterruptedException

Specified by:

doLockExclusively in class NamedLockSupport

Throws:

InterruptedException

doLockShared

private Boolean doLockShared()

doLockExclusively

private Boolean doLockExclusively()

doUnlock

protected void doUnlock()

Specified by:

doUnlock in class NamedLockSupport

anyOtherThreadHasSteps

private boolean anyOtherThreadHasSteps()

Returns true if any other than this thread using this instance has any step recorded.

obtainFileLock

private FileLock obtainFileLock(boolean shared)

Attempts to obtain real FileLock, returns non-null value is succeeds, or null if cannot.