001/*
002 * Copyright 2002-2016 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.scheduling.annotation;
018
019import java.util.concurrent.ExecutionException;
020import java.util.concurrent.Future;
021import java.util.concurrent.TimeUnit;
022
023import org.springframework.util.concurrent.FailureCallback;
024import org.springframework.util.concurrent.ListenableFuture;
025import org.springframework.util.concurrent.ListenableFutureCallback;
026import org.springframework.util.concurrent.SuccessCallback;
027
028/**
029 * A pass-through {@code Future} handle that can be used for method signatures
030 * which are declared with a {@code Future} return type for asynchronous execution.
031 *
032 * <p>As of Spring 4.1, this class implements {@link ListenableFuture}, not just
033 * plain {@link java.util.concurrent.Future}, along with the corresponding support
034 * in {@code @Async} processing.
035 *
036 * <p>As of Spring 4.2, this class also supports passing execution exceptions back
037 * to the caller.
038 *
039 * @author Juergen Hoeller
040 * @author Rossen Stoyanchev
041 * @since 3.0
042 * @see Async
043 * @see #forValue(Object)
044 * @see #forExecutionException(Throwable)
045 */
046public class AsyncResult<V> implements ListenableFuture<V> {
047
048        private final V value;
049
050        private final ExecutionException executionException;
051
052
053        /**
054         * Create a new AsyncResult holder.
055         * @param value the value to pass through
056         */
057        public AsyncResult(V value) {
058                this(value, null);
059        }
060
061        /**
062         * Create a new AsyncResult holder.
063         * @param value the value to pass through
064         */
065        private AsyncResult(V value, ExecutionException ex) {
066                this.value = value;
067                this.executionException = ex;
068        }
069
070
071        @Override
072        public boolean cancel(boolean mayInterruptIfRunning) {
073                return false;
074        }
075
076        @Override
077        public boolean isCancelled() {
078                return false;
079        }
080
081        @Override
082        public boolean isDone() {
083                return true;
084        }
085
086        @Override
087        public V get() throws ExecutionException {
088                if (this.executionException != null) {
089                        throw this.executionException;
090                }
091                return this.value;
092        }
093
094        @Override
095        public V get(long timeout, TimeUnit unit) throws ExecutionException {
096                return get();
097        }
098
099        @Override
100        public void addCallback(ListenableFutureCallback<? super V> callback) {
101                addCallback(callback, callback);
102        }
103
104        @Override
105        public void addCallback(SuccessCallback<? super V> successCallback, FailureCallback failureCallback) {
106                try {
107                        if (this.executionException != null) {
108                                Throwable cause = this.executionException.getCause();
109                                failureCallback.onFailure(cause != null ? cause : this.executionException);
110                        }
111                        else {
112                                successCallback.onSuccess(this.value);
113                        }
114                }
115                catch (Throwable ex) {
116                        // Ignore
117                }
118        }
119
120
121        /**
122         * Create a new async result which exposes the given value from {@link Future#get()}.
123         * @param value the value to expose
124         * @since 4.2
125         * @see Future#get()
126         */
127        public static <V> ListenableFuture<V> forValue(V value) {
128                return new AsyncResult<V>(value, null);
129        }
130
131        /**
132         * Create a new async result which exposes the given exception as an
133         * {@link ExecutionException} from {@link Future#get()}.
134         * @param ex the exception to expose (either an pre-built {@link ExecutionException}
135         * or a cause to be wrapped in an {@link ExecutionException})
136         * @since 4.2
137         * @see ExecutionException
138         */
139        public static <V> ListenableFuture<V> forExecutionException(Throwable ex) {
140                return new AsyncResult<V>(null,
141                                (ex instanceof ExecutionException ? (ExecutionException) ex : new ExecutionException(ex)));
142        }
143
144}