org.apache.tomcat.util.digester.XercesParser.java Source code

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Here is the source code for org.apache.tomcat.util.digester.XercesParser.java

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/* $Id: XercesParser.java 467222 2006-10-24 03:17:11Z markt $
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.tomcat.util.digester;

import java.lang.reflect.Method;
import java.util.Properties;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;

/**
 * Create a <code>SAXParser</code> based on the underlying Xerces version.
 * Currently, Xerces 2.3 and up doesn't implement schema validation the same way
 * 2.1 was. In other to support schema validation in a portable way between 
 * parser, some features/properties need to be set.
 *
 * @since 1.6
 */

public class XercesParser {

    /**
     * The Log to which all SAX event related logging calls will be made.
     */
    protected static Log log = LogFactory.getLog("org.apache.commons.digester.Digester.sax");

    /**
     * The JAXP 1.2 property required to set up the schema location.
     */
    private static final String JAXP_SCHEMA_SOURCE = "http://java.sun.com/xml/jaxp/properties/schemaSource";

    /**
     * The JAXP 1.2 property to set up the schemaLanguage used.
     */
    protected static String JAXP_SCHEMA_LANGUAGE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage";

    /**
     * Xerces dynamic validation property
     */
    protected static String XERCES_DYNAMIC = "http://apache.org/xml/features/validation/dynamic";

    /**
     * Xerces schema validation property
     */
    protected static String XERCES_SCHEMA = "http://apache.org/xml/features/validation/schema";

    /**
     * A <code>float</code> representing the underlying Xerces version
     */
    protected static float version;

    /**
     * The current Xerces version.
     */
    protected static String versionNumber = null;

    /**
     * Return the current Xerces version.
     * @return the current Xerces version.
     */
    private static String getXercesVersion() {
        // If for some reason we can't get the version, set it to 1.0.
        String versionNumber = "1.0";
        try {
            // Use reflection to avoid a build dependency with Xerces.
            Class versionClass = Class.forName("org.apache.xerces.impl.Version");
            // Will return Xerces-J 2.x.0
            Method method = versionClass.getMethod("getVersion", (Class[]) null);
            String version = (String) method.invoke(null, (Object[]) null);
            versionNumber = version.substring("Xerces-J".length(), version.lastIndexOf("."));
        } catch (Exception ex) {
            // Do nothing.
        }
        return versionNumber;
    }

    /**
     * Create a <code>SAXParser</code> based on the underlying
     * <code>Xerces</code> version.
     * @param properties parser specific properties/features
     * @return an XML Schema/DTD enabled <code>SAXParser</code>
     */
    public static SAXParser newSAXParser(Properties properties)
            throws ParserConfigurationException, SAXException, SAXNotSupportedException {

        SAXParserFactory factory = (SAXParserFactory) properties.get("SAXParserFactory");

        if (versionNumber == null) {
            versionNumber = getXercesVersion();
            version = new Float(versionNumber).floatValue();
        }

        // Note: 2.2 is completely broken (with XML Schema). 
        if (version > 2.1) {

            configureXerces(factory);
            return factory.newSAXParser();
        } else {
            SAXParser parser = factory.newSAXParser();
            configureOldXerces(parser, properties);
            return parser;
        }
    }

    /**
     * Configure schema validation as recommended by the JAXP 1.2 spec.
     * The <code>properties</code> object may contains information about
     * the schema local and language. 
     * @param properties parser optional info
     */
    private static void configureOldXerces(SAXParser parser, Properties properties)
            throws ParserConfigurationException, SAXNotSupportedException {

        String schemaLocation = (String) properties.get("schemaLocation");
        String schemaLanguage = (String) properties.get("schemaLanguage");

        try {
            if (schemaLocation != null) {
                parser.setProperty(JAXP_SCHEMA_LANGUAGE, schemaLanguage);
                parser.setProperty(JAXP_SCHEMA_SOURCE, schemaLocation);
            }
        } catch (SAXNotRecognizedException e) {
            log.info(parser.getClass().getName() + ": " + e.getMessage() + " not supported.");
        }

    }

    /**
     * Configure schema validation as recommended by the Xerces spec. 
     * Both DTD and Schema validation will be enabled simultaneously.
     * @param factory SAXParserFactory to be configured
     */
    private static void configureXerces(SAXParserFactory factory)
            throws ParserConfigurationException, SAXNotRecognizedException, SAXNotSupportedException {

        factory.setFeature(XERCES_DYNAMIC, true);
        factory.setFeature(XERCES_SCHEMA, true);

    }
}