Java tutorial
package org.apache.torque.engine.database.transform; /* * 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. */ import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.util.Stack; import java.util.Vector; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.torque.engine.EngineException; import org.apache.torque.engine.database.model.Column; import org.apache.torque.engine.database.model.Database; import org.apache.torque.engine.database.model.Domain; import org.apache.torque.engine.database.model.ForeignKey; import org.apache.torque.engine.database.model.Index; import org.apache.torque.engine.database.model.Table; import org.apache.torque.engine.database.model.Unique; import org.xml.sax.Attributes; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.SAXParseException; import org.xml.sax.helpers.DefaultHandler; /** * A Class that is used to parse an input xml schema file and creates a Database * java structure. * * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a> * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> * @author <a href="mailto:mpoeschl@marmot.at">Martin Poeschl</a> * @author <a href="mailto:dlr@collab.net">Daniel Rall</a> * @author <a href="mailto:fischer@seitenbau.de">Thomas Fischer</a> * @author <a href="mailto:monroe@dukece.com>Greg Monroe</a> * @version $Id: XmlToAppData.java,v 1.1 2007-10-21 07:57:26 abyrne Exp $ */ public class XmlToAppData extends DefaultHandler { /** Logging class from commons.logging */ private static Log log = LogFactory.getLog(XmlToAppData.class); private Database database; private Table currTable; private Column currColumn; private ForeignKey currFK; private Index currIndex; private Unique currUnique; private boolean firstPass; private boolean isExternalSchema; private String currentPackage; private String currentXmlFile; private String defaultPackage; private static SAXParserFactory saxFactory; /** remember all files we have already parsed to detect looping. */ private Vector alreadyReadFiles; /** this is the stack to store parsing data */ private Stack parsingStack = new Stack(); static { saxFactory = SAXParserFactory.newInstance(); saxFactory.setValidating(true); } /** * Creates a new instance for the specified database type. * * @param databaseType The type of database for the application. */ public XmlToAppData(String databaseType) { database = new Database(databaseType); firstPass = true; } /** * Creates a new instance for the specified database type. * * @param databaseType The type of database for the application. * @param defaultPackage the default java package used for the om */ public XmlToAppData(String databaseType, String defaultPackage) { database = new Database(databaseType); this.defaultPackage = defaultPackage; firstPass = true; } /** * Parses a XML input file and returns a newly created and * populated Database structure. * * @param xmlFile The input file to parse. * @return Database populated by <code>xmlFile</code>. */ public Database parseFile(String xmlFile) throws EngineException { try { // in case I am missing something, make it obvious if (!firstPass) { throw new Error("No more double pass"); } // check to see if we alread have parsed the file if ((alreadyReadFiles != null) && alreadyReadFiles.contains(xmlFile)) { return database; } else if (alreadyReadFiles == null) { alreadyReadFiles = new Vector(3, 1); } // remember the file to avoid looping alreadyReadFiles.add(xmlFile); currentXmlFile = xmlFile; SAXParser parser = saxFactory.newSAXParser(); FileInputStream fileInputStream = null; try { fileInputStream = new FileInputStream(xmlFile); } catch (FileNotFoundException fnfe) { throw new FileNotFoundException(new File(xmlFile).getAbsolutePath()); } BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream); try { log.info("Parsing file: '" + (new File(xmlFile)).getName() + "'"); InputSource is = new InputSource(bufferedInputStream); is.setSystemId(new File(xmlFile).getAbsolutePath()); parser.parse(is, this); } finally { bufferedInputStream.close(); } } catch (SAXParseException e) { throw new EngineException("Sax error on line " + e.getLineNumber() + " column " + e.getColumnNumber() + " : " + e.getMessage(), e); } catch (Exception e) { throw new EngineException(e); } if (!isExternalSchema) { firstPass = false; } database.doFinalInitialization(); return database; } /** * EntityResolver implementation. Called by the XML parser * * @param publicId The public identifier of the external entity * @param systemId The system identifier of the external entity * @return an InputSource for the database.dtd file * @see DTDResolver#resolveEntity(String, String) */ public InputSource resolveEntity(String publicId, String systemId) throws SAXException { try { return new DTDResolver().resolveEntity(publicId, systemId); } catch (Exception e) { throw new SAXException(e); } } /** * Handles opening elements of the xml file. * * @param uri * @param localName The local name (without prefix), or the empty string if * Namespace processing is not being performed. * @param rawName The qualified name (with prefix), or the empty string if * qualified names are not available. * @param attributes The specified or defaulted attributes */ public void startElement(String uri, String localName, String rawName, Attributes attributes) throws SAXException { try { if (rawName.equals("database")) { if (isExternalSchema) { currentPackage = attributes.getValue("package"); if (currentPackage == null) { currentPackage = defaultPackage; } } else { database.loadFromXML(attributes); if (database.getPackage() == null) { database.setPackage(defaultPackage); } } } else if (rawName.equals("external-schema")) { String xmlFile = attributes.getValue("filename"); if (xmlFile.charAt(0) != '/') { File f = new File(currentXmlFile); xmlFile = new File(f.getParent(), xmlFile).getPath(); } // put current state onto the stack ParseStackElement.pushState(this); isExternalSchema = true; parseFile(xmlFile); // get the last state from the stack ParseStackElement.popState(this); } else if (rawName.equals("domain")) { Domain domain = new Domain(); domain.loadFromXML(attributes, database.getPlatform()); database.addDomain(domain); } else if (rawName.equals("table")) { currTable = database.addTable(attributes); if (isExternalSchema) { currTable.setForReferenceOnly(true); currTable.setPackage(currentPackage); } } else if (rawName.equals("column")) { currColumn = currTable.addColumn(attributes); } else if (rawName.equals("inheritance")) { currColumn.addInheritance(attributes); } else if (rawName.equals("foreign-key")) { currFK = currTable.addForeignKey(attributes); } else if (rawName.equals("reference")) { currFK.addReference(attributes); } else if (rawName.equals("index")) { currIndex = currTable.addIndex(attributes); } else if (rawName.equals("index-column")) { currIndex.addColumn(attributes); } else if (rawName.equals("unique")) { currUnique = currTable.addUnique(attributes); } else if (rawName.equals("unique-column")) { currUnique.addColumn(attributes); } else if (rawName.equals("id-method-parameter")) { currTable.addIdMethodParameter(attributes); } else if (rawName.equals("option")) { setOption(attributes); } } catch (Exception e) { throw new SAXException(e); } } /** * Handles closing elements of the xml file. * * @param uri * @param localName The local name (without prefix), or the empty string if * Namespace processing is not being performed. * @param rawName The qualified name (with prefix), or the empty string if * qualified names are not available. */ public void endElement(String uri, String localName, String rawName) throws SAXException { if (log.isDebugEnabled()) { log.debug("endElement(" + uri + ", " + localName + ", " + rawName + ") called"); } try { // Reset working objects to null to allow option to know // which element it is associated with. if (rawName.equals("table")) { currTable = null; } else if (rawName.equals("column")) { currColumn = null; } else if (rawName.equals("foreign-key")) { currFK = null; } else if (rawName.equals("index")) { currIndex = null; } else if (rawName.equals("unique")) { currUnique = null; } } catch (Exception e) { throw new SAXException(e); } } public void setOption(Attributes attributes) { // Look thru supported model elements in reverse order to // find one that this option statement applies to. String key = attributes.getValue("key"); String value = attributes.getValue("value"); if (currUnique != null) { currUnique.addOption(key, value); } else if (currIndex != null) { currIndex.addOption(key, value); } else if (currFK != null) { currFK.addOption(key, value); } else if (currColumn != null) { currColumn.addOption(key, value); } else if (currTable != null) { currTable.addOption(key, value); } else { // Must be a db level option. database.addOption(key, value); } } /** * Handles exception which occur when the xml file is parsed * @param e the exception which occured while parsing * @throws SAXException always */ public void error(SAXParseException e) throws SAXException { log.error("Sax parser threw an Exception", e); throw new SAXException("Error while parsing " + currentXmlFile + " at line " + e.getLineNumber() + " column " + e.getColumnNumber() + " : " + e.getMessage()); } /** * When parsing multiple files that use nested <external-schema> tags we * need to use a stack to remember some values. */ private static class ParseStackElement { private boolean isExternalSchema; private String currentPackage; private String currentXmlFile; private boolean firstPass; /** * * @param parser */ public ParseStackElement(XmlToAppData parser) { // remember current state of parent object isExternalSchema = parser.isExternalSchema; currentPackage = parser.currentPackage; currentXmlFile = parser.currentXmlFile; firstPass = parser.firstPass; // push the state onto the stack parser.parsingStack.push(this); } /** * Removes the top element from the stack and activates the stored state * * @param parser */ public static void popState(XmlToAppData parser) { if (!parser.parsingStack.isEmpty()) { ParseStackElement elem = (ParseStackElement) parser.parsingStack.pop(); // activate stored state parser.isExternalSchema = elem.isExternalSchema; parser.currentPackage = elem.currentPackage; parser.currentXmlFile = elem.currentXmlFile; parser.firstPass = elem.firstPass; } } /** * Stores the current state on the top of the stack. * * @param parser */ public static void pushState(XmlToAppData parser) { new ParseStackElement(parser); } } }