com.hazelcast.util

Class ContextMutexFactory

java.lang.Object

com.hazelcast.util.ContextMutexFactory

public final class ContextMutexFactory
extends Object

Provides reference-counted mutexes suitable for synchronization in the context of a supplied object.

Context objects and their associated mutexes are stored in a Map. Client code is responsible to invoke ContextMutexFactory.Mutex.close() on the obtained ContextMutexFactory.Mutex after having synchronized on the mutex; failure to do so will leave an entry residing in the internal Map which may have adverse effects on the ability to garbage collect the context object and the mutex.

The returned ContextMutexFactory.Mutexes implement Closeable, so can be conveniently used in a try-with-resources statement.

Typical usage would allow, for example, synchronizing access to a ConcurrentMap on a per-key basis, to avoid blocking other threads which could perform updates on other entries of the Map.

    class Test {

        private final ContextMutexFactory mutexFactory = new ContextMutexFactory();
        private final ConcurrentMap<String, String> mapToSync = new ConcurrentHashMap<String, String>();

        public String getValueForKey(String key) {
            ContextMutexFactory.Mutex mutex = mutexFactory.mutexFor(key);
            try {
                synchronized (mutex) {
                    // critical section - this thread is the only one trying to add value under this key
                    String value = mapToSync.get(key);
                    if (value == null) {
                        value = ...; // compute the value
                        mapToSync.put(key, value);
                    }
                    return value;
                }
            } finally {
                mutex.close();
            }
        }
    }
 

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	ContextMutexFactory.Mutex Reference counted mutex, which will remove itself from the mutexMap when it is no longer referenced.

Constructor Summary

Constructors

Constructor and Description
ContextMutexFactory()

Method Summary

Modifier and Type	Method and Description
ContextMutexFactory.Mutex	mutexFor(Object mutexKey)

Methods inherited from class java.lang.Object

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

Constructor Detail

ContextMutexFactory

public ContextMutexFactory()

Method Detail

mutexFor

public ContextMutexFactory.Mutex mutexFor(Object mutexKey)