Java tutorial
/* * Copyright 2004-2008 the original author or authors. * * Licensed 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.springframework.webflow.engine.model.builder.xml; import java.io.IOException; import java.io.InputStream; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.core.io.Resource; import org.springframework.util.xml.SimpleSaxErrorHandler; import org.w3c.dom.Document; import org.xml.sax.EntityResolver; import org.xml.sax.SAXException; /** * The default document loader strategy for XSD-based XML documents with validation enabled by default. * <p> * Note: full XSD support requires JDK 5.0 or a capable parser such as Xerces 2.0. JDK 1.4 or < do not fully support XSD * out of the box. To use this implementation on JDK 1.4 make sure Xerces is available in your classpath or disable XSD * validation by {@link #setValidating(boolean) setting the validating property to false}. * * @author Keith Donald */ public class DefaultDocumentLoader implements DocumentLoader { private static final Log logger = LogFactory.getLog(DefaultDocumentLoader.class); /** * JAXP attribute used to configure the schema language for validation. */ private static final String SCHEMA_LANGUAGE_ATTRIBUTE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage"; /** * JAXP attribute value indicating the XSD schema language. */ private static final String XSD_SCHEMA_LANGUAGE = "http://www.w3.org/2001/XMLSchema"; /** * Flag indicating if the XML document parser will perform schema validation. */ private boolean validating = true; /** * The spring-webflow schema resolution strategy. */ private EntityResolver entityResolver = new WebFlowEntityResolver(); /** * Returns whether or not the XML parser will validate the document. */ public boolean isValidating() { return validating; } /** * Set if the XML parser should validate the document and thus enforce a schema. Defaults to true. */ public void setValidating(boolean validating) { this.validating = validating; } /** * Returns the SAX entity resolver used by the XML parser. */ public EntityResolver getEntityResolver() { return entityResolver; } /** * Set a SAX entity resolver to be used for parsing. Can be overridden for custom entity resolution, for example * relative to some specific base path. */ public void setEntityResolver(EntityResolver entityResolver) { this.entityResolver = entityResolver; } public Document loadDocument(Resource resource) throws IOException, ParserConfigurationException, SAXException { InputStream is = null; try { is = resource.getInputStream(); DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setValidating(isValidating()); factory.setNamespaceAware(true); try { factory.setAttribute(SCHEMA_LANGUAGE_ATTRIBUTE, XSD_SCHEMA_LANGUAGE); } catch (IllegalArgumentException ex) { throw new IllegalStateException("Unable to validate using XSD: Your JAXP provider [" + factory + "] does not support XML Schema. " + "Are you running on Java 1.4 or below with Apache Crimson? " + "If so you must upgrade to Apache Xerces (or Java 5 or >) for full XSD support."); } DocumentBuilder docBuilder = factory.newDocumentBuilder(); docBuilder.setErrorHandler(new SimpleSaxErrorHandler(logger)); docBuilder.setEntityResolver(getEntityResolver()); return docBuilder.parse(is); } finally { if (is != null) { is.close(); } } } }