1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20 package org.apache.commons.pipeline.util;
21
22 /**
23 * An implementation of this interface should define a strategy that will
24 * allow a unique identifier to be generated for an object. This identifier
25 * may be mutually comparable with identifiers generated for a different
26 * object type; it is used to permit signalling between drivers in
27 * separate pipeline branches.
28 *
29 *
30 */
31 public interface KeyFactory<T,K> {
32 /**
33 * Generates a unique identifier of type K for an object of type T.
34 * @return the newly created identifier
35 */
36 public K generateKey(T source);
37
38 /**
39 * Trivial key factory that produces the object's hash code as a key.
40 */
41 public static class HashKeyFactory implements KeyFactory<Object,Integer> {
42 public Integer generateKey(Object source) {
43 return source.hashCode();
44 }
45 }
46 }