001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.activemq.filter;
018
019 import java.io.IOException;
020 import java.lang.reflect.Constructor;
021 import java.lang.reflect.InvocationTargetException;
022 import java.util.ArrayList;
023 import java.util.List;
024 import java.util.Map;
025 import java.util.Properties;
026
027 import javax.jms.JMSException;
028 import javax.xml.parsers.DocumentBuilder;
029 import javax.xml.parsers.DocumentBuilderFactory;
030 import javax.xml.parsers.ParserConfigurationException;
031
032 import org.apache.activemq.command.Message;
033 import org.apache.activemq.util.JMSExceptionSupport;
034 import org.slf4j.Logger;
035 import org.slf4j.LoggerFactory;
036
037 /**
038 * Used to evaluate an XPath Expression in a JMS selector.
039 */
040 public final class XPathExpression implements BooleanExpression {
041
042 private static final Logger LOG = LoggerFactory.getLogger(XPathExpression.class);
043 private static final String EVALUATOR_SYSTEM_PROPERTY = "org.apache.activemq.XPathEvaluatorClassName";
044 private static final String DEFAULT_EVALUATOR_CLASS_NAME = XalanXPathEvaluator.class.getName();
045 public static final String DOCUMENT_BUILDER_FACTORY_FEATURE = "org.apache.activemq.documentBuilderFactory.feature";
046
047 private static final Constructor EVALUATOR_CONSTRUCTOR;
048 private static DocumentBuilder builder = null;
049
050 static {
051 String cn = System.getProperty(EVALUATOR_SYSTEM_PROPERTY, DEFAULT_EVALUATOR_CLASS_NAME);
052 Constructor m = null;
053 try {
054 try {
055 m = getXPathEvaluatorConstructor(cn);
056 DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
057 builderFactory.setNamespaceAware(true);
058 builderFactory.setIgnoringElementContentWhitespace(true);
059 builderFactory.setIgnoringComments(true);
060 try {
061 // set some reasonable defaults
062 builderFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);
063 builderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
064 builderFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
065 } catch (ParserConfigurationException e) {
066 LOG.warn("Error setting document builder factory feature", e);
067 }
068 // setup the feature from the system property
069 setupFeatures(builderFactory);
070 builder = builderFactory.newDocumentBuilder();
071 } catch (Throwable e) {
072 LOG.warn("Invalid " + XPathEvaluator.class.getName() + " implementation: " + cn + ", reason: " + e, e);
073 cn = DEFAULT_EVALUATOR_CLASS_NAME;
074 try {
075 m = getXPathEvaluatorConstructor(cn);
076 } catch (Throwable e2) {
077 LOG.error("Default XPath evaluator could not be loaded", e);
078 }
079 }
080 } finally {
081 EVALUATOR_CONSTRUCTOR = m;
082 }
083 }
084
085 private final String xpath;
086 private final XPathEvaluator evaluator;
087
088 public static interface XPathEvaluator {
089 boolean evaluate(Message message) throws JMSException;
090 }
091
092 XPathExpression(String xpath) {
093 this.xpath = xpath;
094 this.evaluator = createEvaluator(xpath);
095 }
096
097 private static Constructor getXPathEvaluatorConstructor(String cn) throws ClassNotFoundException, SecurityException, NoSuchMethodException {
098 Class c = XPathExpression.class.getClassLoader().loadClass(cn);
099 if (!XPathEvaluator.class.isAssignableFrom(c)) {
100 throw new ClassCastException("" + c + " is not an instance of " + XPathEvaluator.class);
101 }
102 return c.getConstructor(new Class[] {String.class, DocumentBuilder.class});
103 }
104
105 protected static void setupFeatures(DocumentBuilderFactory factory) {
106 Properties properties = System.getProperties();
107 List<String> features = new ArrayList<String>();
108 for (Map.Entry<Object, Object> prop : properties.entrySet()) {
109 String key = (String) prop.getKey();
110 if (key.startsWith(DOCUMENT_BUILDER_FACTORY_FEATURE)) {
111 String uri = key.split(DOCUMENT_BUILDER_FACTORY_FEATURE + ":")[1];
112 Boolean value = Boolean.valueOf((String)prop.getValue());
113 try {
114 factory.setFeature(uri, value);
115 features.add("feature " + uri + " value " + value);
116 } catch (ParserConfigurationException e) {
117 LOG.warn("DocumentBuilderFactory doesn't support the feature {} with value {}, due to {}.", new Object[]{uri, value, e});
118 }
119 }
120 }
121 if (features.size() > 0) {
122 StringBuffer featureString = new StringBuffer();
123 // just log the configured feature
124 for (String feature : features) {
125 if (featureString.length() != 0) {
126 featureString.append(", ");
127 }
128 featureString.append(feature);
129 }
130 }
131
132 }
133
134 private XPathEvaluator createEvaluator(String xpath2) {
135 try {
136 return (XPathEvaluator)EVALUATOR_CONSTRUCTOR.newInstance(new Object[] {xpath, builder});
137 } catch (InvocationTargetException e) {
138 Throwable cause = e.getCause();
139 if (cause instanceof RuntimeException) {
140 throw (RuntimeException)cause;
141 }
142 throw new RuntimeException("Invalid XPath Expression: " + xpath + " reason: " + e.getMessage(), e);
143 } catch (Throwable e) {
144 throw new RuntimeException("Invalid XPath Expression: " + xpath + " reason: " + e.getMessage(), e);
145 }
146 }
147
148 public Object evaluate(MessageEvaluationContext message) throws JMSException {
149 try {
150 if (message.isDropped()) {
151 return null;
152 }
153 return evaluator.evaluate(message.getMessage()) ? Boolean.TRUE : Boolean.FALSE;
154 } catch (IOException e) {
155 throw JMSExceptionSupport.create(e);
156 }
157
158 }
159
160 public String toString() {
161 return "XPATH " + ConstantExpression.encodeString(xpath);
162 }
163
164 /**
165 * @param message
166 * @return true if the expression evaluates to Boolean.TRUE.
167 * @throws JMSException
168 */
169 public boolean matches(MessageEvaluationContext message) throws JMSException {
170 Object object = evaluate(message);
171 return object != null && object == Boolean.TRUE;
172 }
173
174 }