1 /*
2 * Copyright 2006-2010 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.springframework.batch.poller;
17
18 import java.util.concurrent.Callable;
19 import java.util.concurrent.Future;
20
21 /**
22 * Interface for polling a {@link Callable} instance provided by the user. Use
23 * when you need to put something in the background (e.g. a remote invocation)
24 * and wait for the result, e.g.
25 *
26 * <pre>
27 * Poller<Result> poller = ...
28 *
29 * final long id = remoteService.execute(); // do something remotely
30 *
31 * Future<Result> future = poller.poll(new Callable<Result> {
32 * public Object call() {
33 * // Look for the result (null if not ready)
34 * return remoteService.get(id);
35 * }
36 * });
37 *
38 * Result result = future.get(1000L, TimeUnit.MILLSECONDS);
39 * </pre>
40 *
41 * @author Dave Syer
42 *
43 */
44 public interface Poller<T> {
45
46 /**
47 * Use the callable provided to poll for a non-null result. The callable
48 * might be executed multiple times searching for a result, but once either
49 * a result or an exception has been observed the polling stops.
50 *
51 * @param callable a {@link Callable} to use to retrieve a result
52 * @return a future which itself can be used to get the result
53 *
54 */
55 Future<T> poll(Callable<T> callable) throws Exception;
56
57 }