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Java > Open Source Codes > org > apache > velocity > anakia > XPathCache


1 package org.apache.velocity.anakia;
2
3 /*
4  * Copyright 2001,2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * 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, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import com.werken.xpath.XPath;
20 import java.util.Map JavaDoc;
21 import java.util.WeakHashMap JavaDoc;
22
23 /**
24  * Provides a cache for XPath expressions. Used by {@link NodeList} and
25  * {@link AnakiaElement} to minimize XPath parsing in their
26  * <code>selectNodes()</code> methods.
27  *
28  * @author <a HREF="mailto:szegedia@freemail.hu">Attila Szegedi</a>
29  * @version $Id: XPathCache.java,v 1.1.10.1 2004/03/03 23:22:04 geirm Exp $
30  */
31 class XPathCache
32 {
33     // Cache of already parsed XPath expressions, keyed by String representations
34 // of the expression as passed to getXPath().
35 private static final Map JavaDoc XPATH_CACHE = new WeakHashMap JavaDoc();
36
37     private XPathCache()
38     {
39     }
40     
41     /**
42      * Returns an XPath object representing the requested XPath expression.
43      * A cached object is returned if it already exists for the requested expression.
44      * @param xpathString the XPath expression to parse
45      * @return the XPath object that represents the parsed XPath expression.
46      */
47     static XPath getXPath(String JavaDoc xpathString)
48     {
49         XPath xpath = null;
50         synchronized(XPATH_CACHE)
51         {
52             xpath = (XPath)XPATH_CACHE.get(xpathString);
53             if(xpath == null)
54             {
55                 xpath = new XPath(xpathString);
56                 XPATH_CACHE.put(xpathString, xpath);
57             }
58         }
59         return xpath;
60     }
61 }
62
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