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
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
FieldsModifier and TypeFieldDescriptionprivate final ReentrantLock
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
TheFileChannel
this instance is about.private final AtomicReference<FileLock>
The reference ofFileLock
, if obtained.private static final long
private static final long
private static final long
Thread -> steps stack (true = shared, false = exclusive)Fields inherited from class org.eclipse.aether.named.support.NamedLockSupport
logger
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Constructor Summary
ConstructorsConstructorDescriptionFileLockNamedLock
(String name, FileChannel fileChannel, NamedLockFactorySupport factory) -
Method Summary
Modifier and TypeMethodDescriptionprivate boolean
Returnstrue
if any other than this thread using this instance has any step recorded.private Boolean
private Boolean
boolean
lockExclusively
(long time, TimeUnit unit) Tries to lock exclusively, may block for given time.boolean
lockShared
(long time, TimeUnit unit) Tries to lock shared, may block for given time.private FileLock
obtainFileLock
(boolean shared) Attempts to obtain realFileLock
, returns non-null value is succeeds, ornull
if cannot.void
unlock()
Unlocks the lock, must be invoked by caller after one of theNamedLock.lockShared(long, TimeUnit)
orNamedLock.lockExclusively(long, TimeUnit)
.Methods inherited from class org.eclipse.aether.named.support.NamedLockSupport
close, name
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Field Details
-
RETRY_SLEEP_MILLIS
private static final long RETRY_SLEEP_MILLIS- See Also:
-
LOCK_POSITION
private static final long LOCK_POSITION- See Also:
-
LOCK_SIZE
private static final long LOCK_SIZE- See Also:
-
threadSteps
Thread -> steps stack (true = shared, false = exclusive) -
fileChannel
TheFileChannel
this instance is about. -
fileLockRef
The reference ofFileLock
, if obtained. -
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
-
-
Method Details
-
lockExclusively
Description copied from interface:NamedLock
Tries to lock exclusively, may block for given time. If successful, returnstrue
.- Throws:
InterruptedException
-
doLockExclusively
-
unlock
public void unlock()Description copied from interface:NamedLock
Unlocks the lock, must be invoked by caller after one of theNamedLock.lockShared(long, TimeUnit)
orNamedLock.lockExclusively(long, TimeUnit)
. -
anyOtherThreadHasSteps
private boolean anyOtherThreadHasSteps()Returnstrue
if any other than this thread using this instance has any step recorded. -
obtainFileLock
Attempts to obtain realFileLock
, returns non-null value is succeeds, ornull
if cannot.