初探guava 執行緒回撥
阿新 • • 發佈：2019-05-05
程式碼
public class ExecutorFactor { /*固定執行緒池數量，MoreExecutors只是為原有的執行緒池做代理而已，且包裝成ListeningExecutorService 這種型別 ，下面在submit才能返回ListenableFuture 型別的future*/ private static ListeningExecutorService EXECUTOR_SERVICE = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool()); public static void exec(final FutureService objService, final Object... args) { // 非同步處理 ListenableFuture<Object> future = EXECUTOR_SERVICE.submit( new Callable<Object>() { public Object call() throws Exception { Object o = objService.handler(args); return o; } }); Futures.addCallback(future,new FutureCallback<Object>() { @Override public void onSuccess(Object o) { // TODO 成功處理 objService.onSuccess(o, args); } @Override public void onFailure(Throwable throwable) { // TODO 失敗處理 objService.onFailure(throwable, args); } },EXECUTOR_SERVICE); } }
這裡我們不妨看下Futures 是如何新增listener 的，點進去
public static <V> void addCallback(
final ListenableFuture<V> future,
final FutureCallback<? super V> callback,
//。。。
這裡我們看下CallbackListener這個類
future.addListener(new CallbackListener<V>(future, callback), executor);
}
private static final class CallbackListener<V> implements Runnable {
//發現是個Runnable 型別的類，那麼主要看它的run方法
@Override
public void run() {
final V value;
try {
value = getDone(future);
} catch (ExecutionException e) {
//如果發生異常就呼叫異常回調
callback.onFailure(e.getCause());
return;
} catch (RuntimeException e) {
callback.onFailure(e);
return;
} catch (Error e) {
callback.onFailure(e);
return;
}
//如果正常就呼叫正常回調
callback.onSuccess(value);
}
}