Class ListenerCallQueue<L>
java.lang.Object
com.google.common.util.concurrent.ListenerCallQueue<L>
A list of listeners for implementing a concurrency friendly observable object.
Listeners are registered once via addListener(L, java.util.concurrent.Executor)
and then may be invoked by enqueueing and then dispatching events.
The API of this class is designed to make it easy to achieve the following properties
- Multiple events for the same listener are never dispatched concurrently.
- Events for the different listeners are dispatched concurrently.
- All events for a given listener dispatch on the provided
invalid reference
#executor
- It is easy for the user to ensure that listeners are never invoked while holding locks.
directExecutor()
or be otherwise re-entrant (call back into your
object). So it is important to not call dispatch()
while holding any locks. This is why
enqueue(com.google.common.util.concurrent.ListenerCallQueue.Event<L>)
and dispatch()
are 2 different methods. It is expected that the decision
to run a particular event is made during the state change, but the decision to actually invoke
the listeners can be delayed slightly so that locks can be dropped. Also, because dispatch()
is expected to be called concurrently, it is idempotent.-
Nested Class Summary
Nested ClassesModifier and TypeClassDescription(package private) static interface
Method reference-compatible listener event.private static final class
A special purpose queue/executor that dispatches listener events serially on a configured executor. -
Field Summary
FieldsModifier and TypeFieldDescriptionprivate final List
<ListenerCallQueue.PerListenerQueue<L>> private static final LazyLogger
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
addListener
(L listener, Executor executor) Adds a listener that will be called using the given executor when events are laterenqueued
anddispatched
.void
dispatch()
Dispatches all events enqueued prior to this call, serially and in order, for every listener.void
enqueue
(ListenerCallQueue.Event<L> event) Enqueues an event to be run on currently known listeners.void
enqueue
(ListenerCallQueue.Event<L> event, String label) Enqueues an event to be run on currently known listeners, with a label.private void
enqueueHelper
(ListenerCallQueue.Event<L> event, Object label)
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Field Details
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logger
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listeners
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Constructor Details
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ListenerCallQueue
ListenerCallQueue()
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Method Details
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addListener
Adds a listener that will be called using the given executor when events are laterenqueued
anddispatched
. -
enqueue
Enqueues an event to be run on currently known listeners.The
toString
method of the Event itself will be used to describe the event in the case of an error.- Parameters:
event
- the callback to execute ondispatch()
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enqueue
Enqueues an event to be run on currently known listeners, with a label.- Parameters:
event
- the callback to execute ondispatch()
label
- a description of the event to use in the case of an error
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enqueueHelper
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dispatch
public void dispatch()Dispatches all events enqueued prior to this call, serially and in order, for every listener.Note: this method is idempotent and safe to call from any thread
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