Module io.helidon.integrations.cdi.referencecountedcontext

Package io.helidon.integrations.cdi.referencecountedcontext

Class ReferenceCountedContext

java.lang.Object

io.helidon.integrations.cdi.referencecountedcontext.ReferenceCountedContext

All Implemented Interfaces:

AlterableContext, Context

public final class ReferenceCountedContext
extends Object
implements AlterableContext

A somewhat special-purpose AlterableContext that destroys a contextual instance when its thread-specific reference count drops to zero or less than zero.

A contextual instance's thread-specific reference count is incremented when either the get(Contextual) or get(Contextual, CreationalContext) method is called. It is decremented when the obtained instance is passed to the decrementReferenceCount(Contextual) method, which is indirectly and solely responsible for that instance's ultimate removal from this ReferenceCountedContext.

Internally, the destroy(Contextual) method simply calls decrementReferenceCount(Contextual).

Thread Safety

Instances of this class are safe for concurrent use by multiple threads.

See Also:

decrementReferenceCount(Contextual), destroy(Contextual), get(Contextual, CreationalContext), ReferenceCounted

Method Summary

Modifier and Type	Method	Description
int	decrementReferenceCount(Contextual<?> c)	Decrements the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual, destroying the instance if and only if the reference count becomes less than or equal to zero, and returns the resulting reference count.
int	decrementReferenceCount(Contextual<?> c, int amount)	Decrements the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual, destroying the instance if and only if the reference count becomes less than or equal to zero, and returns the resulting reference count.
void	destroy(Contextual<?> contextual)	Calls the decrementReferenceCount(Contextual) method with the supplied Contextual, destroying it if and only if its thread-specific reference count becomes less than or equal to zero.
<T> T	get(Contextual<T> contextual)	Returns the contextual instance associated with the current thread and the supplied Contextual, or null if no such contextual instance exists.
<T> T	get(Contextual<T> contextual, CreationalContext<T> cc)	Returns the contextual instance associated with the current thread and the supplied Contextual, creating it if necessary.
static ReferenceCountedContext	getInstanceFrom(BeanManager beanManager)	Returns the sole ReferenceCountedContext that is registered with the supplied BeanManager.
int	getReferenceCount(Contextual<?> c)	Returns the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual.
Class<? extends Annotation>	getScope()	Returns ReferenceCounted.class when invoked.
boolean	isActive()	Returns true when invoked.

Methods inherited from class java.lang.Object

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

Method Detail

decrementReferenceCount

public int decrementReferenceCount(Contextual<?> c)

Decrements the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual, destroying the instance if and only if the reference count becomes less than or equal to zero, and returns the resulting reference count.

Parameters:

c - the Contextual whose instance's reference count should be decremented; may be null in which case no action will be taken and 0 will be returned

Returns:

the resulting reference count

See Also:

Contextual.destroy(Object, CreationalContext), get(Contextual, CreationalContext)

decrementReferenceCount

public int decrementReferenceCount(Contextual<?> c,
                                   int amount)

Decrements the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual, destroying the instance if and only if the reference count becomes less than or equal to zero, and returns the resulting reference count.

Most users will never have to call this method.

Parameters:

c - the Contextual whose instance's reference count should be decremented; may be null in which case no action will be taken and 0 will be returned

amount - the amount by which to decrement; must be greater than or (trivially) equal to 0

Returns:

the resulting reference count

Throws:

IllegalArgumentException - if amount is less than 0

See Also:

Contextual.destroy(Object, CreationalContext), get(Contextual, CreationalContext), decrementReferenceCount(Contextual)

getReferenceCount

public int getReferenceCount(Contextual<?> c)

Returns the reference count of the contextual instance, if any, associated with the combination of the current thread and the supplied Contextual.

Most users will never have to call this method.

This method never returns a negative number.

Parameters:

c - the Contextual whose instance's reference count should be returned; may be null in which case 0 will be returned

Returns:

the reference count in question; never a negative number

destroy

public void destroy(Contextual<?> contextual)

Calls the decrementReferenceCount(Contextual) method with the supplied Contextual, destroying it if and only if its thread-specific reference count becomes less than or equal to zero.

Specified by:

destroy in interface AlterableContext

Parameters:

contextual - the Contextual to destroy; may be null in which case no action will be taken

See Also:

decrementReferenceCount(Contextual), get(Contextual, CreationalContext)

get

public <T> T get(Contextual<T> contextual)

Returns the contextual instance associated with the current thread and the supplied Contextual, or null if no such contextual instance exists.

Specified by:

get in interface Context

Parameters:

contextual - the Contextual in question; may be null in which case null wil be returned

Returns:

the contextual instance associated with the current thread and the supplied Contextual, or null

get

public <T> T get(Contextual<T> contextual,
                 CreationalContext<T> cc)

Returns the contextual instance associated with the current thread and the supplied Contextual, creating it if necessary.

Specified by:

get in interface Context

Parameters:

contextual - the Contextual in question; may be null in which case null wil be returned

cc - a CreationalContext that will hold dependent instances; may be null

Returns:

the contextual instance associated with the current thread and the supplied Contextual; may strictly speaking be null but normally is not

getScope

public Class<? extends Annotation> getScope()

Returns ReferenceCounted.class when invoked.

Specified by:

getScope in interface Context

Returns:

ReferenceCounted.class in all cases

isActive

public boolean isActive()

Returns true when invoked.

Specified by:

isActive in interface Context

Returns:

true in all cases

getInstanceFrom

public static ReferenceCountedContext getInstanceFrom(BeanManager beanManager)

Returns the sole ReferenceCountedContext that is registered with the supplied BeanManager.

Strictly speaking, this method may return null if the ReferenceCountedExtension has been deliberately disabled and hence has not had a chance to install a ReferenceCountedContext. In all normal usage this method will not return null.

Parameters:

beanManager - the BeanManager whose ReferenceCountedContext should be returned; must not be null

Returns:

a ReferenceCountedContext, or null in exceptionally rare situations

Throws:

NullPointerException - if beanManager is null