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.XMLConstants;
029import javax.xml.parsers.DocumentBuilder;
030import javax.xml.parsers.DocumentBuilderFactory;
031import javax.xml.parsers.ParserConfigurationException;
032
033import org.apache.activemq.command.Message;
034import org.apache.activemq.util.JMSExceptionSupport;
035import org.slf4j.Logger;
036import org.slf4j.LoggerFactory;
037
038/**
039 * Used to evaluate an XPath Expression in a JMS selector.
040 */
041public final class XPathExpression implements BooleanExpression {
042
043    private static final Logger LOG = LoggerFactory.getLogger(XPathExpression.class);
044    private static final String EVALUATOR_SYSTEM_PROPERTY = "org.apache.activemq.XPathEvaluatorClassName";
045    private static final String DEFAULT_EVALUATOR_CLASS_NAME = "org.apache.activemq.filter.JAXPXPathEvaluator";
046    public static final String DOCUMENT_BUILDER_FACTORY_FEATURE = "org.apache.activemq.documentBuilderFactory.feature";
047
048    private static final Constructor EVALUATOR_CONSTRUCTOR;
049    private static DocumentBuilder builder = null;
050
051    static {
052        String cn = System.getProperty(EVALUATOR_SYSTEM_PROPERTY, DEFAULT_EVALUATOR_CLASS_NAME);
053        Constructor m = null;
054        try {
055            try {
056                m = getXPathEvaluatorConstructor(cn);
057                DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
058                builderFactory.setNamespaceAware(true);
059                builderFactory.setIgnoringElementContentWhitespace(true);
060                builderFactory.setIgnoringComments(true);
061                try {
062                    // set some reasonable defaults
063                    builderFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, Boolean.TRUE);
064                    builderFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);
065                    builderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
066                    builderFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
067                } catch (ParserConfigurationException e) {
068                    LOG.warn("Error setting document builder factory feature", e);
069                }
070                // setup the feature from the system property
071                setupFeatures(builderFactory);
072                builder = builderFactory.newDocumentBuilder();
073            } catch (Throwable e) {
074                LOG.warn("Invalid " + XPathEvaluator.class.getName() + " implementation: " + cn + ", reason: " + e, e);
075                cn = DEFAULT_EVALUATOR_CLASS_NAME;
076                try {
077                    m = getXPathEvaluatorConstructor(cn);
078                } catch (Throwable e2) {
079                    LOG.error("Default XPath evaluator could not be loaded", e);
080                }
081            }
082        } finally {
083            EVALUATOR_CONSTRUCTOR = m;
084        }
085    }
086
087    private final String xpath;
088    private final XPathEvaluator evaluator;
089
090    public static interface XPathEvaluator {
091        boolean evaluate(Message message) throws JMSException;
092    }
093
094    XPathExpression(String xpath) {
095        this.xpath = xpath;
096        this.evaluator = createEvaluator(xpath);
097    }
098
099    private static Constructor getXPathEvaluatorConstructor(String cn) throws ClassNotFoundException, SecurityException, NoSuchMethodException {
100        Class c = XPathExpression.class.getClassLoader().loadClass(cn);
101        if (!XPathEvaluator.class.isAssignableFrom(c)) {
102            throw new ClassCastException("" + c + " is not an instance of " + XPathEvaluator.class);
103        }
104        return c.getConstructor(new Class[] {String.class, DocumentBuilder.class});
105    }
106
107    protected static void setupFeatures(DocumentBuilderFactory factory) {
108        Properties properties = System.getProperties();
109        List<String> features = new ArrayList<String>();
110        for (Map.Entry<Object, Object> prop : properties.entrySet()) {
111            String key = (String) prop.getKey();
112            if (key.startsWith(DOCUMENT_BUILDER_FACTORY_FEATURE)) {
113                String uri = key.split(DOCUMENT_BUILDER_FACTORY_FEATURE + ":")[1];
114                Boolean value = Boolean.valueOf((String)prop.getValue());
115                try {
116                    factory.setFeature(uri, value);
117                    features.add("feature " + uri + " value " + value);
118                } catch (ParserConfigurationException e) {
119                    LOG.warn("DocumentBuilderFactory doesn't support the feature {} with value {}, due to {}.", new Object[]{uri, value, e});
120                }
121            }
122        }
123        if (features.size() > 0) {
124            StringBuffer featureString = new StringBuffer();
125            // just log the configured feature
126            for (String feature : features) {
127                if (featureString.length() != 0) {
128                    featureString.append(", ");
129                }
130                featureString.append(feature);
131            }
132        }
133
134    }
135
136    private XPathEvaluator createEvaluator(String xpath2) {
137        try {
138            return (XPathEvaluator)EVALUATOR_CONSTRUCTOR.newInstance(new Object[] {xpath, builder});
139        } catch (InvocationTargetException e) {
140            Throwable cause = e.getCause();
141            if (cause instanceof RuntimeException) {
142                throw (RuntimeException)cause;
143            }
144            throw new RuntimeException("Invalid XPath Expression: " + xpath + " reason: " + e.getMessage(), e);
145        } catch (Throwable e) {
146            throw new RuntimeException("Invalid XPath Expression: " + xpath + " reason: " + e.getMessage(), e);
147        }
148    }
149
150    public Object evaluate(MessageEvaluationContext message) throws JMSException {
151        try {
152            if (message.isDropped()) {
153                return null;
154            }
155            return evaluator.evaluate(message.getMessage()) ? Boolean.TRUE : Boolean.FALSE;
156        } catch (IOException e) {
157            throw JMSExceptionSupport.create(e);
158        }
159
160    }
161
162    public String toString() {
163        return "XPATH " + ConstantExpression.encodeString(xpath);
164    }
165
166    /**
167     * @param message
168     * @return true if the expression evaluates to Boolean.TRUE.
169     * @throws JMSException
170     */
171    public boolean matches(MessageEvaluationContext message) throws JMSException {
172        Object object = evaluate(message);
173        return object != null && object == Boolean.TRUE;
174    }
175
176}