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本文次要钻研一下cheddar的PendingResult
PendingResult
Cheddar/cheddar/cheddar-application/src/main/java/com/clicktravel/cheddar/application/pending/result/PendingResult.java
class PendingResult { private static final long TIMEOUT_SECONDS = 30; private final CountDownLatch countdownLatch = new CountDownLatch(1); private Result result; /** * Offers a {@link Result}, returning immediately. * @param result {@link Result} to offer */ public void offerResult(final Result result) { this.result = result; countdownLatch.countDown(); } /** * Polls for a {@link Result}, blocking until it is offered by some other thread. If the result has already been * offered, the result is returned immediately. * @return {@link Result} obtained, potentially after blocking * @throws InterruptedException, PendingResultTimeoutException */ public Result pollResult() throws InterruptedException, PendingResultTimeoutException { if (!countdownLatch.await(TIMEOUT_SECONDS, TimeUnit.SECONDS)) { throw new PendingResultTimeoutException(); } return result; }}PendingResult定义了offerResult、pollResult办法；offerResult办法设置result，而后通过countdownLatch通过pollResult；pollResult办法期待TIMEOUT_SECONDS，若还没有后果抛出PendingResultTimeoutException
PendingResultHandler
Cheddar/cheddar/cheddar-application/src/main/java/com/clicktravel/cheddar/application/pending/result/PendingResultHandler.java
@Componentpublic class PendingResultHandler { private final PendingResultsHolder pendingResultsHolder; private final String applicationName; private final XStream xStream = new XStream(); @Autowired public PendingResultHandler(final PendingResultsHolder pendingResultsHolder, @Value("${server.application.name}") final String applicationName) { this.pendingResultsHolder = pendingResultsHolder; this.applicationName = applicationName; } /** * Creates a {@link PendingResult} stored on the local application instance * @return pendingResultId Unique identifier of created {@PendingResult} */ public String createPendingResult() { return pendingResultsHolder.create(); } /** * Removes a {@link PendingResult} stored on the local application instance * @param pendingResultId ID of {@link PendingResult} to remove */ public void removePendingResult(final String pendingResultId) { pendingResultsHolder.remove(pendingResultId); } /** * Polls a {@link PendingResult} stored on the local application instance for a returned value, blocking until a * value is offered or an exception is thrown * @param pendingResultId ID of locally stored {@link PendingResult} * @return Value from returned result * @throws Exception If exception was thrown */ public Object pollValue(final String pendingResultId) throws Exception { final PendingResult pendingResult = pendingResultsHolder.get(pendingResultId); return pendingResult.pollResult().getValue(); } /** * Offers a return value for a {@link PendingResult}, which is possibly stored on a different (remote) application * instance * @param pendingResultId ID of {@link PendingResult} to offer value to * @param value Value to offer */ public void offerValue(final String pendingResultId, final Object value) { offerResult(pendingResultId, new SimpleResult(value)); } /** * Offers a thrown exception for a {@link PendingResult}, which is possibly stored on a different (remote) * application instance * @param pendingResultId of {@link PendingResult} to offer thrown exception to * @param exception Thrown exception to offer */ public void offerException(final String pendingResultId, final Exception exception) { offerResult(pendingResultId, new ExceptionResult(exception)); } private void offerResult(final String pendingResultId, final Result result) { final PendingResultOfferedEvent event = new PendingResultOfferedEvent(); event.setTargetApplicationName(applicationName); event.setPendingResultId(pendingResultId); event.setResultXml(toCompactXml(result)); SystemEventPublisher.instance().publishEvent(event); } private String toCompactXml(final Object object) { final StringWriter stringWriter = new StringWriter(); xStream.marshal(object, new CompactWriter(stringWriter)); return stringWriter.toString(); }}PendingResultHandler提供了removePendingResult、pollValue、offerValue、offerException办法；offerResult办法创立并公布PendingResultOfferedEvent
小结
cheddar的PendingResult定义了offerResult、pollResult办法；PendingResultHandler提供了removePendingResult、pollValue、offerValue、offerException办法。
doc
- Cheddar