1 /***
2 * Copyright 2003-2010 Terracotta, Inc.
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
17 package net.sf.ehcache.search.attribute;
18
19 import java.io.Serializable;
20
21 import net.sf.ehcache.Element;
22
23 /***
24 * Used to extract a search attribute value for a given cache element.<br>
25 * <br>
26 * Instances must be {@link Serializable} in order to ensure identical
27 * extractors are used in distributed caches
28 *
29 * @author teck
30 */
31 public interface AttributeExtractor extends Serializable {
32
33 /***
34 * Extract the attribute value. The instance returned from this method must
35 * be one of:
36 * <ul>
37 * <li>java.lang.Boolean
38 * <li>java.lang.Byte
39 * <li>java.lang.Character
40 * <li>java.lang.Double
41 * <li>java.lang.Float
42 * <li>java.lang.Integer
43 * <li>java.lang.Long
44 * <li>java.lang.Short
45 * <li>java.lang.String
46 * <li>java.util.Date
47 * <li>java.sql.Date
48 * <li>java.lang.Enum
49 * </ul>
50 * <p/>
51 * NOTE: null is a legal return here as well indicating that this attribute will not be available for the given element
52 *
53 * @param element the cache element to inspect
54 * @param attributeName the name of the requested attribute
55 * @return the attribute value
56 * @throws AttributeExtractorException if the attribute cannot be found or extracted
57 */
58 Object attributeFor(Element element, String attributeName) throws AttributeExtractorException;
59 }