org.springframework.scheduling.annotation.AsyncResult Maven / Gradle / Ivy
/*
* Copyright 2002-2018 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
*
* https://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.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import org.springframework.lang.Nullable;
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.
*
* 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.
*
*
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
* @param the value type
* @see Async
* @see #forValue(Object)
* @see #forExecutionException(Throwable)
*/
public class AsyncResult implements ListenableFuture {
@Nullable
private final V value;
@Nullable
private final Throwable executionException;
/**
* Create a new AsyncResult holder.
* @param value the value to pass through
*/
public AsyncResult(@Nullable V value) {
this(value, null);
}
/**
* Create a new AsyncResult holder.
* @param value the value to pass through
*/
private AsyncResult(@Nullable V value, @Nullable Throwable 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
@Nullable
public V get() throws ExecutionException {
if (this.executionException != null) {
throw (this.executionException instanceof ExecutionException ?
(ExecutionException) this.executionException :
new ExecutionException(this.executionException));
}
return this.value;
}
@Override
@Nullable
public V get(long timeout, TimeUnit unit) throws ExecutionException {
return get();
}
@Override
public void addCallback(ListenableFutureCallback callback) {
addCallback(callback, callback);
}
@Override
public void addCallback(SuccessCallback successCallback, FailureCallback failureCallback) {
try {
if (this.executionException != null) {
failureCallback.onFailure(exposedException(this.executionException));
}
else {
successCallback.onSuccess(this.value);
}
}
catch (Throwable ex) {
// Ignore
}
}
@Override
public CompletableFuture completable() {
if (this.executionException != null) {
CompletableFuture completable = new CompletableFuture<>();
completable.completeExceptionally(exposedException(this.executionException));
return completable;
}
else {
return CompletableFuture.completedFuture(this.value);
}
}
/**
* 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 ListenableFuture 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 ListenableFuture forExecutionException(Throwable ex) {
return new AsyncResult<>(null, ex);
}
/**
* Determine the exposed exception: either the cause of a given
* {@link ExecutionException}, or the original exception as-is.
* @param original the original as given to {@link #forExecutionException}
* @return the exposed exception
*/
private static Throwable exposedException(Throwable original) {
if (original instanceof ExecutionException) {
Throwable cause = original.getCause();
if (cause != null) {
return cause;
}
}
return original;
}
}