org.glassfish.jersey.internal.util.collection.DataStructures Maven / Gradle / Ivy
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package org.glassfish.jersey.internal.util.collection;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.glassfish.jersey.internal.util.JdkVersion;
/**
* Utility class, which tries to pickup the best collection implementation depending
* on running environment.
*
* @author Gustav Trede
* @author Marek Potociar (marek.potociar at oracle.com)
* @since 2.3
*/
public final class DataStructures {
private static final Class LTQ_CLASS;
static {
String className = null;
Class c;
try {
final JdkVersion jdkVersion = JdkVersion.getJdkVersion();
final JdkVersion minimumVersion = JdkVersion.parseVersion("1.7.0");
className = (minimumVersion.compareTo(jdkVersion) <= 0)
? "java.util.concurrent.LinkedTransferQueue"
: "org.glassfish.jersey.internal.util.collection.LinkedTransferQueue";
c = getAndVerify(className);
Logger.getLogger(DataStructures.class.getName()).log(Level.FINE, "USING LTQ class:{0}", c);
} catch (final Throwable t) {
Logger.getLogger(DataStructures.class.getName()).log(Level.FINE,
"failed loading data structure class:" + className
+ " fallback to embedded one", t);
c = LinkedBlockingQueue.class; // fallback to LinkedBlockingQueue
}
LTQ_CLASS = c;
}
/**
* Default concurrency level calculated based on the number of available CPUs.
*/
public static final int DEFAULT_CONCURENCY_LEVEL = ceilingNextPowerOfTwo(Runtime.getRuntime().availableProcessors());
private static int ceilingNextPowerOfTwo(final int x) {
// Hacker's Delight, Chapter 3, Harry S. Warren Jr.
return 1 << (Integer.SIZE - Integer.numberOfLeadingZeros(x - 1));
}
private static Class getAndVerify(final String cn) throws Throwable {
try {
return AccessController.doPrivileged(new PrivilegedExceptionAction>() {
@Override
public Class run() throws Exception {
return DataStructures.class.getClassLoader().loadClass(cn).newInstance().getClass();
}
});
} catch (final PrivilegedActionException ex) {
throw ex.getCause();
}
}
/**
* Create an instance of a {@link BlockingQueue} that is based on
* {@code LinkedTransferQueue} implementation from JDK 7.
*
* When running on JDK 7 or higher, JDK {@code LinkedTransferQueue} implementation is used,
* on JDK 6 an internal Jersey implementation class is used.
*
*
* @param the type of elements held in the queue.
* @return new instance of a {@link BlockingQueue} that is based on {@code LinkedTransferQueue}
* implementation from JDK 7.
*/
@SuppressWarnings("unchecked")
public static BlockingQueue createLinkedTransferQueue() {
try {
return AccessController.doPrivileged(new PrivilegedExceptionAction>() {
@Override
public BlockingQueue run() throws Exception {
return (BlockingQueue) LTQ_CLASS.newInstance();
}
});
} catch (final PrivilegedActionException ex) {
final Throwable cause = ex.getCause();
if (cause instanceof RuntimeException) {
throw (RuntimeException) cause;
} else {
throw new RuntimeException(cause);
}
}
}
/**
* Creates a new, empty map with a default initial capacity (16),
* load factor (0.75) and concurrencyLevel (16).
*
* On Oracle JDK, the factory method will return an instance of
*
* {@code ConcurrentHashMapV8}
* that is supposed to be available in JDK 8 and provides better performance and memory characteristics than
* {@link ConcurrentHashMap} implementation from JDK 7 or earlier. On non-Oracle JDK,
* the factory instantiates the standard {@code ConcurrentHashMap} from JDK.
*
*
* @return the map.
*/
public static ConcurrentMap createConcurrentMap() {
return JdkVersion.getJdkVersion().isUnsafeSupported()
? new ConcurrentHashMapV8()
: new ConcurrentHashMap();
}
/**
* Creates a new map with the same mappings as the given map.
*
* On Oracle JDK, the factory method will return an instance of
*
* {@code ConcurrentHashMapV8}
* that is supposed to be available in JDK 8 and provides better performance and memory characteristics than
* {@link ConcurrentHashMap} implementation from JDK 7 or earlier. On non-Oracle JDK,
* the factory instantiates the standard {@code ConcurrentHashMap} from JDK.
*
*
* @param map the map.
*/
public static ConcurrentMap createConcurrentMap(
final Map map) {
return JdkVersion.getJdkVersion().isUnsafeSupported()
? new ConcurrentHashMapV8(map)
: new ConcurrentHashMap(map);
}
/**
* Creates a new, empty map with an initial table size accommodating the specified
* number of elements without the need to dynamically resize.
*
* On Oracle JDK, the factory method will return an instance of
*
* {@code ConcurrentHashMapV8}
* that is supposed to be available in JDK 8 and provides better performance and memory characteristics than
* {@link ConcurrentHashMap} implementation from JDK 7 or earlier. On non-Oracle JDK,
* the factory instantiates the standard {@code ConcurrentHashMap} from JDK.
*
*
* @param initialCapacity The implementation performs internal
* sizing to accommodate this many elements.
* @throws IllegalArgumentException if the initial capacity of
* elements is negative.
*/
public static ConcurrentMap createConcurrentMap(
final int initialCapacity) {
return JdkVersion.getJdkVersion().isUnsafeSupported()
? new ConcurrentHashMapV8(initialCapacity)
: new ConcurrentHashMap(initialCapacity);
}
/**
* Creates a new, empty map with an initial table size based on the given number of elements
* ({@code initialCapacity}), table density ({@code loadFactor}), and number of concurrently
* updating threads ({@code concurrencyLevel}).
*
* On Oracle JDK, the factory method will return an instance of
*
* {@code ConcurrentHashMapV8}
* that is supposed to be available in JDK 8 and provides better performance and memory characteristics than
* {@link ConcurrentHashMap} implementation from JDK 7 or earlier. On non-Oracle JDK,
* the factory instantiates the standard {@code ConcurrentHashMap} from JDK.
*
*
* @param initialCapacity the initial capacity. The implementation
* performs internal sizing to accommodate this many elements,
* given the specified load factor.
* @param loadFactor the load factor (table density) for
* establishing the initial table size.
* @param concurrencyLevel the estimated number of concurrently
* updating threads. The implementation may use this value as
* a sizing hint.
* @throws IllegalArgumentException if the initial capacity is
* negative or the load factor or concurrencyLevel are
* not positive.
*/
public static ConcurrentMap createConcurrentMap(
final int initialCapacity, final float loadFactor,
final int concurrencyLevel) {
return JdkVersion.getJdkVersion().isUnsafeSupported()
? new ConcurrentHashMapV8(initialCapacity, loadFactor, concurrencyLevel)
: new ConcurrentHashMap(initialCapacity, loadFactor, concurrencyLevel);
}
}