Package com.github.mike10004.xvfbmanager

Class Poller<T>

java.lang.Object

com.github.mike10004.xvfbmanager.Poller<T>

Type Parameters:

T - type of content returned upon resolution

Direct Known Subclasses:

Poller.SimplePoller

public abstract class Poller<T>
extends Object

Class that facilitates polling for an arbitrary condition. Polling is the act of repeatedly querying the state at defined intervals. Polling stops when this poller's evaluation function answers with a reason to stop, or the iterator of intervals to wait between polls is exhausted. Reasons to stop include resolution, meaning the poller is satisfied with the result, or abortion meaning polling must stop early without a resolution.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Poller.PollAction	Enumeration of actions a poller's check function can return.
static class	Poller.PollAnswer<E>	Class that represents an answer in response to a poll request.
static class	Poller.PollOutcome<E>	Class that represents the outcome of a poll.
protected static class	Poller.RegularIntervals
protected static class	Poller.SimplePoller
static class	Poller.StopReason	Enmeration of reasons that polling stopped.

Constructor Summary

Constructors

Modifier	Constructor	Description
	Poller()	Creates a new poller.
protected	Poller(Sleeper sleeper)

Method Summary

Modifier and Type	Method	Description
protected static <E> Poller.PollAnswer<E>	abortPolling()
protected static <E> Poller.PollAnswer<E>	abortPolling(E value)
protected abstract Poller.PollAnswer<T>	check(int pollAttemptsSoFar)	Checks whether the state being questioned has been resolved.
static Poller<Void>	checking(Supplier<Boolean> condition)	Creates a simple poller that evaluates a condition on each poll.
protected static <E> Poller.PollAnswer<E>	continuePolling()
Poller.PollOutcome<T>	poll(long intervalMs, int maxNumPolls)	Polls at regular intervals.
Poller.PollOutcome<T>	poll(Iterator<Long> intervalsMs)	Starts polling and returns an outcome when polling stops.
protected static <E> Poller.PollAnswer<E>	resolve(E value)

Methods inherited from class java.lang.Object

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

Constructor Detail

Poller

public Poller()

Creates a new poller. The poller waits between polls using the default Sleeper. Subclasses can use an alternate sleeper, is helpful if you want to test your poller without actually waiting.

Poller

protected Poller(Sleeper sleeper)

Method Detail

poll

public Poller.PollOutcome<T> poll(long intervalMs,
                                  int maxNumPolls)
                           throws InterruptedException

Polls at regular intervals.

Parameters:

intervalMs - the interval in milliseconds

maxNumPolls - the maximum number of polls to be executed

Returns:

the poll outcome

Throws:

InterruptedException - if waiting is interrupted

poll

public Poller.PollOutcome<T> poll(Iterator<Long> intervalsMs)
                           throws InterruptedException

Starts polling and returns an outcome when polling stops.

Parameters:

intervalsMs - an iterator of interval lengths in milliseconds

Returns:

the poll outcome

Throws:

InterruptedException - if waiting is interrupted

resolve

protected static <E> Poller.PollAnswer<E> resolve(@Nullable
                                                  E value)

continuePolling

protected static <E> Poller.PollAnswer<E> continuePolling()

abortPolling

protected static <E> Poller.PollAnswer<E> abortPolling(@Nullable
                                                       E value)

abortPolling

protected static <E> Poller.PollAnswer<E> abortPolling()

check

protected abstract Poller.PollAnswer<T> check(int pollAttemptsSoFar)

Checks whether the state being questioned has been resolved. Subclasses must override this method to return an answer that may or may not contain a content object. In a conventional implementation, if the state has been resolved, this method would return an answer with content object representing a resolution along with Poller.PollAction.RESOLVE; if the state has not yet been resolved, this method would return null as the answer content along with Poller.PollAction.CONTINUE if we should continue polling or Poller.PollAction.ABORT if polling should stop immediately anyway.

Implementations of this method should return an answer constructed with the continuePolling(), abortPolling(), or resolve(Object) methods.

Unconventional implementations may elect to return a non-null content object with Poller.PollAction.ABORT to provide the poll() caller a degenerate answer, perhaps indicating why state will never be resolved.

Parameters:

pollAttemptsSoFar - the number of poll attempts prior to this poll attempt

Returns:

a poll answer

checking

public static Poller<Void> checking(Supplier<Boolean> condition)

Creates a simple poller that evaluates a condition on each poll.

Parameters:

condition - the condition to evaluate; poll will be resolved if it returns true, and if it returns false, the poller will keep polling

Returns:

the poller