1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.http.impl.client.cache.memcached;
28
29
30 /**
31 * This is a {@link KeyHashingScheme} decorator that simply adds
32 * a known prefix to the results of another {@code KeyHashingScheme}.
33 * Primarily useful for namespacing a shared memcached cluster, for
34 * example.
35 */
36 public class PrefixKeyHashingScheme implements KeyHashingScheme {
37
38 private final String prefix;
39 private final KeyHashingScheme backingScheme;
40
41 /**
42 * Creates a new {@link KeyHashingScheme} that prepends the given
43 * prefix to the results of hashes from the given backing scheme.
44 * Users should be aware that memcached has a fixed maximum key
45 * length, so the combination of this prefix plus the results of
46 * the backing hashing scheme must still fit within these limits.
47 * @param prefix
48 * @param backingScheme
49 */
50 public PrefixKeyHashingScheme(final String prefix, final KeyHashingScheme backingScheme) {
51 this.prefix = prefix;
52 this.backingScheme = backingScheme;
53 }
54
55 @Override
56 public String hash(final String storageKey) {
57 return prefix + backingScheme.hash(storageKey);
58 }
59
60 }