/* * Copyright 2002-2016 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.scheduling.annotation; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import org.springframework.util.concurrent.FailureCallback; import org.springframework.util.concurrent.ListenableFuture; import org.springframework.util.concurrent.ListenableFutureCallback; import org.springframework.util.concurrent.SuccessCallback; /** * A pass-through {@code Future} handle that can be used for method signatures * which are declared with a {@code Future} return type for asynchronous execution. * * <p>As of Spring 4.1, this class implements {@link ListenableFuture}, not just * plain {@link java.util.concurrent.Future}, along with the corresponding support * in {@code @Async} processing. * * <p>As of Spring 4.2, this class also supports passing execution exceptions back * to the caller. * * @author Juergen Hoeller * @author Rossen Stoyanchev * @since 3.0 * @see Async * @see #forValue(Object) * @see #forExecutionException(Throwable) */ public class AsyncResult<V> implements ListenableFuture<V> { private final V value; private final ExecutionException executionException; /** * Create a new AsyncResult holder. * @param value the value to pass through */ public AsyncResult(V value) { this(value, null); } /** * Create a new AsyncResult holder. * @param value the value to pass through */ private AsyncResult(V value, ExecutionException ex) { this.value = value; this.executionException = ex; } @Override public boolean cancel(boolean mayInterruptIfRunning) { return false; } @Override public boolean isCancelled() { return false; } @Override public boolean isDone() { return true; } @Override public V get() throws ExecutionException { if (this.executionException != null) { throw this.executionException; } return this.value; } @Override public V get(long timeout, TimeUnit unit) throws ExecutionException { return get(); } @Override public void addCallback(ListenableFutureCallback<? super V> callback) { addCallback(callback, callback); } @Override public void addCallback(SuccessCallback<? super V> successCallback, FailureCallback failureCallback) { try { if (this.executionException != null) { Throwable cause = this.executionException.getCause(); failureCallback.onFailure(cause != null ? cause : this.executionException); } else { successCallback.onSuccess(this.value); } } catch (Throwable ex) { // Ignore } } /** * Create a new async result which exposes the given value from {@link Future#get()}. * @param value the value to expose * @since 4.2 * @see Future#get() */ public static <V> ListenableFuture<V> forValue(V value) { return new AsyncResult<>(value, null); } /** * Create a new async result which exposes the given exception as an * {@link ExecutionException} from {@link Future#get()}. * @param ex the exception to expose (either an pre-built {@link ExecutionException} * or a cause to be wrapped in an {@link ExecutionException}) * @since 4.2 * @see ExecutionException */ public static <V> ListenableFuture<V> forExecutionException(Throwable ex) { return new AsyncResult<>(null, (ex instanceof ExecutionException ? (ExecutionException) ex : new ExecutionException(ex))); } }