Package com.inductiveautomation.perspective.gateway.driven

Class LockGuardedDrivenValue<T>

java.lang.Object

com.inductiveautomation.perspective.gateway.driven.LockGuardedDrivenValue<T>

Type Parameters:

T - The type of the driven value

All Implemented Interfaces:

DrivenValue<T>

Direct Known Subclasses:

ExpressionDrivenValue, LockGuardedDrivenValueCollection

public abstract class LockGuardedDrivenValue<T>
extends java.lang.Object
implements DrivenValue<T>

A LockGuardedDrivenValue is a DrivenValue which holds a lock object and asserts that Threads which call isReady(), isDirty(), and getAndClear() hold this lock. Client code must synchronize on the lock before calling any of these methods.

See Also:

Thread.holdsLock(Object)

Field Summary

Fields

Modifier and Type	Field	Description
protected java.lang.Object	lock

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	LockGuardedDrivenValue(java.lang.Object lock)

Method Summary

Modifier and Type	Method	Description
java.util.Optional<T>	getAndClear()	Fetch the current driven value
protected abstract java.util.Optional<T>	getAndClearInternal()	Called after asserting that the calling thread holds the injected lock.
boolean	isDirty()
protected abstract boolean	isDirtyInternal()	Called after asserting that the calling thread holds the injected lock.
boolean	isReady()
protected abstract boolean	isReadyInternal()	Called after asserting that the calling thread holds the injected lock.
java.util.Collection<PropertyReference>	resolveReferences()	Call before startup() to resolve and collect any references this value might depend on.
protected abstract java.util.Collection<PropertyReference>	resolveReferencesInternal()

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.inductiveautomation.perspective.gateway.driven.DrivenValue

shutdown, startup

Field Detail

lock

protected final java.lang.Object lock

Constructor Detail

LockGuardedDrivenValue

protected LockGuardedDrivenValue(@Nonnull
                                 java.lang.Object lock)

Method Detail

isReadyInternal

protected abstract boolean isReadyInternal()

Called after asserting that the calling thread holds the injected lock.

See Also:

isReady()

isReady

public boolean isReady()

Specified by:

isReady in interface DrivenValue<T>

Returns:

true if the driven value is ready to fetch

isDirtyInternal

protected abstract boolean isDirtyInternal()

Called after asserting that the calling thread holds the injected lock.

See Also:

isDirty()

isDirty

public boolean isDirty()

Specified by:

isDirty in interface DrivenValue<T>

Returns:

true if the driven value has changed since the last time it was fetched

resolveReferencesInternal

protected abstract java.util.Collection<PropertyReference> resolveReferencesInternal()

resolveReferences

public java.util.Collection<PropertyReference> resolveReferences()

Description copied from interface: DrivenValue

Call before startup() to resolve and collect any references this value might depend on.

Specified by:

resolveReferences in interface DrivenValue<T>

getAndClearInternal

@Nonnull
protected abstract java.util.Optional<T> getAndClearInternal()

Called after asserting that the calling thread holds the injected lock.

See Also:

getAndClear()

getAndClear

@Nonnull
public java.util.Optional<T> getAndClear()

Description copied from interface: DrivenValue

Fetch the current driven value

Specified by:

getAndClear in interface DrivenValue<T>

Returns:

An Optional containing the current driven value, if present, or an empty Optional if the driven value is null / not present.