1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.lang3.concurrent;
18
19 /**
20 * <p>
21 * Definition of an interface for the thread-safe initialization of objects.
22 * </p>
23 * <p>
24 * The idea behind this interface is to provide access to an object in a
25 * thread-safe manner. A {@code ConcurrentInitializer} can be passed to multiple
26 * threads which can all access the object produced by the initializer. Through
27 * the {@link #get()} method the object can be queried.
28 * </p>
29 * <p>
30 * Concrete implementations of this interface will use different strategies for
31 * the creation of the managed object, e.g. lazy initialization or
32 * initialization in a background thread. This is completely transparent to
33 * client code, so it is possible to change the initialization strategy without
34 * affecting clients.
35 * </p>
36 *
37 * @since 3.0
38 * @version $Id: ConcurrentInitializer.java 1088899 2011-04-05 05:31:27Z bayard $
39 * @param <T> the type of the object managed by this initializer class
40 */
41 public interface ConcurrentInitializer<T> {
42 /**
43 * Returns the fully initialized object produced by this {@code
44 * ConcurrentInitializer}. A concrete implementation here returns the
45 * results of the initialization process. This method may block until
46 * results are available. Typically, once created the result object is
47 * always the same.
48 *
49 * @return the object created by this {@code ConcurrentException}
50 * @throws ConcurrentException if an error occurred during initialization of
51 * the object
52 */
53 T get() throws ConcurrentException;
54 }