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 */ 017package org.apache.activemq.filter; 018 019import java.io.IOException; 020import java.lang.reflect.Constructor; 021import java.lang.reflect.InvocationTargetException; 022import java.util.ArrayList; 023import java.util.List; 024import java.util.Map; 025import java.util.Properties; 026 027import javax.jms.JMSException; 028import javax.xml.parsers.DocumentBuilder; 029import javax.xml.parsers.DocumentBuilderFactory; 030import javax.xml.parsers.ParserConfigurationException; 031 032import org.apache.activemq.command.Message; 033import org.apache.activemq.util.JMSExceptionSupport; 034import org.slf4j.Logger; 035import org.slf4j.LoggerFactory; 036 037/** 038 * Used to evaluate an XPath Expression in a JMS selector. 039 */ 040public 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 = "org.apache.activemq.filter.XalanXPathEvaluator"; 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}