1 /*
2 * Copyright 2006 the original author or authors.
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 org.springframework.xml.xpath;
18
19 import java.util.Collections;
20 import java.util.Map;
21
22 import org.apache.commons.logging.Log;
23 import org.apache.commons.logging.LogFactory;
24
25 import org.springframework.util.Assert;
26 import org.springframework.util.ClassUtils;
27 import org.springframework.xml.JaxpVersion;
28
29 /**
30 * Factory for compiled <code>XPathExpression</code>s, being aware of JAXP 1.3+ XPath functionality, and Jaxen. Mainly
31 * for internal use of the framework.
32 * <p/>
33 * The goal of this class is to avoid runtime dependencies a specific XPath engine, simply using the best XPath
34 * implementation that is available. Prefers JAXP 1.3+ XPath implementations to Jaxen.
35 *
36 * @author Arjen Poutsma
37 * @see XPathExpression
38 * @since 1.0.0
39 */
40 public abstract class XPathExpressionFactory {
41
42 private static final Log logger = LogFactory.getLog(XPathExpressionFactory.class);
43
44 private static final String JAXEN_CLASS_NAME = "org.jaxen.XPath";
45
46 private static boolean jaxp13Available;
47
48 private static boolean jaxenAvailable;
49
50 static {
51 // Check whether JAXP 1.3 is available
52 jaxp13Available = JaxpVersion.isAtLeastJaxp13();
53
54 // Check whether Jaxen is available
55 try {
56 ClassUtils.forName(JAXEN_CLASS_NAME);
57 jaxenAvailable = true;
58 }
59 catch (ClassNotFoundException ex) {
60 jaxenAvailable = false;
61 }
62 }
63
64 /**
65 * Create a compiled XPath expression using the given string.
66 *
67 * @param expression the XPath expression
68 * @return the compiled XPath expression
69 * @throws IllegalStateException if neither JAXP 1.3+, or Jaxen are available
70 * @throws XPathParseException if the given expression cannot be parsed
71 */
72 public static XPathExpression createXPathExpression(String expression)
73 throws IllegalStateException, XPathParseException {
74 return createXPathExpression(expression, Collections.EMPTY_MAP);
75 }
76
77 /**
78 * Create a compiled XPath expression using the given string and namespaces. The namespace map should consist of
79 * string prefixes mapped to string namespaces.
80 *
81 * @param expression the XPath expression
82 * @param namespaces a map that binds string prefixes to string namespaces
83 * @return the compiled XPath expression
84 * @throws IllegalStateException if neither JAXP 1.3+, or Jaxen are available
85 * @throws XPathParseException if the given expression cannot be parsed
86 */
87 public static XPathExpression createXPathExpression(String expression, Map namespaces)
88 throws IllegalStateException, XPathParseException {
89 Assert.hasLength(expression, "expression is empty");
90 if (jaxp13Available) {
91 try {
92 logger.trace("Creating [javax.xml.xpath.XPathExpression]");
93 return Jaxp13XPathExpressionFactory.createXPathExpression(expression, namespaces);
94 }
95 catch (XPathException e) {
96 throw e;
97 }
98 catch (Throwable e) {
99 jaxp13Available = false;
100 }
101 }
102 if (jaxenAvailable) {
103 logger.trace("Creating [org.jaxen.XPath]");
104 return JaxenXPathExpressionFactory.createXPathExpression(expression, namespaces);
105 }
106 throw new IllegalStateException(
107 "Could not create XPathExpression: could not locate JAXP 1.3, or Jaxen on the class path");
108 }
109
110
111 }