Package org.jruby.javasupport.util

Class ObjectProxyCache<T,A>

java.lang.Object

org.jruby.javasupport.util.ObjectProxyCache<T,A>

public abstract class ObjectProxyCache<T,A>
extends Object

Maps Java objects to their proxies. Combines elements of WeakHashMap and ConcurrentHashMap to permit unsynchronized reads. May be configured to use either Weak (the default) or Soft references.

Note that both Java objects and their proxies are held by weak/soft references; because proxies (currently) keep strong references to their Java objects, if we kept strong references to them the Java objects would never be gc'ed. This presents a problem in the case where a user passes a Rubified Java object out to Java but keeps no reference in Ruby to the proxy; if the object is returned to Ruby after its proxy has been gc'ed, a new (and possibly very wrong, in the case of JRuby-defined subclasses) proxy will be created. Use of soft references may help reduce the likelihood of this occurring; users may be advised to keep Ruby-side references to prevent it occurring altogether.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	ObjectProxyCache.Entry<T>
private static interface	ObjectProxyCache.EntryRef<T>
static enum	ObjectProxyCache.ReferenceType
(package private) static class	ObjectProxyCache.Segment<T,A>
private static final class	ObjectProxyCache.SoftEntryRef<T>
private static final class	ObjectProxyCache.WeakEntryRef<T>

Field Summary

Fields

Modifier and Type	Field	Description
private static int	_nextId
private static final float	DEFAULT_LOAD_FACTOR
private static final int	DEFAULT_SEGMENT_SIZE
private static final int	DEFAULT_SEGMENTS
private final int	id
private static final Logger	LOG
private static final int	MAX_CAPACITY
private static final int	MAX_SEGMENTS
private final ObjectProxyCache.ReferenceType	referenceType
private final int	segmentMask
private final ObjectProxyCache.Segment<T,A>[]	segments
private final int	segmentShift
private static final int	VULTURE_RUN_FREQ_SECONDS

Constructor Summary

Constructors

Constructor	Description
ObjectProxyCache()
ObjectProxyCache(int numSegments, int initialSegCapacity, ObjectProxyCache.ReferenceType refType)
ObjectProxyCache(ObjectProxyCache.ReferenceType refType)

Method Summary

Modifier and Type	Method	Description
abstract T	allocateProxy(Object javaObject, A allocator)
T	get(Object javaObject)
T	getOrCreate(Object javaObject, A allocator)
private static int	hash(Object javaObject)
private static int	nextId()
void	put(Object javaObject, T proxy)
private ObjectProxyCache.Segment<T,A>	segmentFor(int hash)
int	size()	Returns the approximate size (elements in use) of the cache.
String	stats()

Methods inherited from class java.lang.Object

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

Field Details

LOG

private static final Logger LOG

DEFAULT_SEGMENTS

private static final int DEFAULT_SEGMENTS

See Also:

• Constant Field Values

DEFAULT_SEGMENT_SIZE

private static final int DEFAULT_SEGMENT_SIZE

See Also:

• Constant Field Values

DEFAULT_LOAD_FACTOR

private static final float DEFAULT_LOAD_FACTOR

See Also:

• Constant Field Values

MAX_CAPACITY

private static final int MAX_CAPACITY

See Also:

• Constant Field Values

MAX_SEGMENTS

private static final int MAX_SEGMENTS

See Also:

• Constant Field Values

VULTURE_RUN_FREQ_SECONDS

private static final int VULTURE_RUN_FREQ_SECONDS

See Also:

• Constant Field Values

_nextId

private static int _nextId

referenceType

private final ObjectProxyCache.ReferenceType referenceType

segments

private final ObjectProxyCache.Segment<T,A>[] segments

segmentShift

private final int segmentShift

segmentMask

private final int segmentMask

id

private final int id

Constructor Details

ObjectProxyCache

public ObjectProxyCache()

ObjectProxyCache

public ObjectProxyCache(ObjectProxyCache.ReferenceType refType)

ObjectProxyCache

public ObjectProxyCache(int numSegments,
 int initialSegCapacity,
 ObjectProxyCache.ReferenceType refType)

Method Details

nextId

private static int nextId()

allocateProxy

public abstract T allocateProxy(Object javaObject,
 A allocator)

get

public T get(Object javaObject)

getOrCreate

public T getOrCreate(Object javaObject,
 A allocator)

put

public void put(Object javaObject,
 T proxy)

hash

private static int hash(Object javaObject)

segmentFor

private ObjectProxyCache.Segment<T,A> segmentFor(int hash)

size

public int size()

Returns the approximate size (elements in use) of the cache. The sizes of the segments are summed. No effort is made to synchronize across segments, so the value returned may differ from the actual size at any point in time.

Returns:

stats

public String stats()