Java tutorial
/********************************************************************************** * $URL: https://source.sakaiproject.org/svn/kernel/trunk/kernel-util/src/main/java/org/sakaiproject/util/Xml.java $ * $Id: Xml.java 90064 2011-03-19 12:04:59Z david.horwitz@uct.ac.za $ *********************************************************************************** * * Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008 Sakai Foundation * * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.sakaiproject.util; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.Reader; import java.io.StringReader; import java.io.StringWriter; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.w3c.dom.DOMImplementation; import org.w3c.dom.Document; import org.w3c.dom.ls.DOMImplementationLS; import org.w3c.dom.ls.LSOutput; import org.w3c.dom.ls.LSSerializer; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; /** * Special utils used in the storage utils * (some duplication from the other kernel Xml utils) */ public class StorageUtils { private static Log M_log = LogFactory.getLog(StorageUtils.class); private static SAXParserFactory parserFactory; /** * Create a new DOM Document. * * @return A new DOM document. */ public static Document createDocument() { try { DocumentBuilder builder = getDocumentBuilder(); Document doc = builder.newDocument(); return doc; } catch (Exception any) { M_log.warn("createDocument: " + any.toString()); return null; } } /** * Read a DOM Document from xml in a file. * * @param name * The file name for the xml file. * @return A new DOM Document with the xml contents. */ public static Document readDocument(String name) { Document doc = null; // first try using whatever character encoding the XML itself specifies InputStream fis = null; try { DocumentBuilder docBuilder = getDocumentBuilder(); fis = new FileInputStream(name); doc = docBuilder.parse(fis); } catch (Exception e) { doc = null; } finally { if (fis != null) { try { fis.close(); } catch (IOException e) { } } } if (doc != null) return doc; // OK, that didn't work - the document is probably ISO-8859-1 try { DocumentBuilder docBuilder = getDocumentBuilder(); InputStreamReader in = new InputStreamReader(new FileInputStream(name), "ISO-8859-1"); InputSource inputSource = new InputSource(in); doc = docBuilder.parse(inputSource); } catch (Exception any) { doc = null; } if (doc != null) return doc; // try forcing UTF-8 try { DocumentBuilder docBuilder = getDocumentBuilder(); InputStreamReader in = new InputStreamReader(new FileInputStream(name), "UTF-8"); InputSource inputSource = new InputSource(in); doc = docBuilder.parse(inputSource); } catch (Exception any) { M_log.warn("readDocument failed on file: " + name + " with exception: " + any.toString()); doc = null; } return doc; } /** * Read a DOM Document from xml in a string. * * @param in * The string containing the XML * @return A new DOM Document with the xml contents. */ public static Document readDocumentFromString(String in) { try { DocumentBuilder docBuilder = getDocumentBuilder(); InputSource inputSource = new InputSource(new StringReader(in)); Document doc = docBuilder.parse(inputSource); return doc; } catch (Exception any) { M_log.warn("readDocumentFromString: " + any.toString()); return null; } } /** * Process a string of XML using SAX and a default handler * @param in * @param dh * @throws SAXException * @throws IOException */ public static void processString(String in, DefaultHandler dh) throws SAXException, IOException { Reader r = new StringReader(in); processReader(r, dh); r.close(); } /** * SAX Process a Reader using the Default handler * @param in * @param dh * @throws SAXException * @throws IOException */ public static void processReader(Reader in, DefaultHandler dh) throws SAXException, IOException { InputSource ss = new InputSource(in); SAXParser p = null; if (parserFactory == null) { parserFactory = SAXParserFactory.newInstance(); parserFactory.setNamespaceAware(false); parserFactory.setValidating(false); } try { p = parserFactory.newSAXParser(); } catch (ParserConfigurationException e) { throw new SAXException("Failed to get a parser ", e); } p.parse(ss, dh); } /** * Write a DOM Document to an xml file. * * @param doc * The DOM Document to write. * @param fileName * The complete file name path. */ public static void writeDocument(Document doc, String fileName) { OutputStream out = null; try { out = new FileOutputStream(fileName); // get an instance of the DOMImplementation registry DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); DOMImplementation impl = builder.getDOMImplementation(); DOMImplementationLS feature = (DOMImplementationLS) impl.getFeature("LS", "3.0"); LSSerializer serializer = feature.createLSSerializer(); LSOutput output = feature.createLSOutput(); output.setByteStream(out); output.setEncoding("UTF-8"); serializer.write(doc, output); out.close(); } catch (Exception any) { M_log.warn("writeDocument: " + any.toString()); } finally { if (out != null) { try { out.close(); } catch (IOException e) { } } } } /** * Write a DOM Document to an output stream. * * @param doc * The DOM Document to write. * @param out * The output stream. */ public static String writeDocumentToString(Document doc) { try { StringWriter sw = new StringWriter(); DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); DOMImplementation impl = builder.getDOMImplementation(); DOMImplementationLS feature = (DOMImplementationLS) impl.getFeature("LS", "3.0"); LSSerializer serializer = feature.createLSSerializer(); LSOutput output = feature.createLSOutput(); output.setCharacterStream(sw); output.setEncoding("UTF-8"); serializer.write(doc, output); sw.flush(); return sw.toString(); } catch (Exception any) { M_log.warn("writeDocumentToString: " + any.toString()); return null; } } /** * Escape the SQL to ensure it is valid (and protect against SQL injection attacks) * @param value SQL string or fragment * @return escaped SQL string */ public static String escapeSql(String value) { if (value == null) return ""; try { StringBuilder buf = new StringBuilder(); for (int i = 0; i < value.length(); i++) { char c = value.charAt(i); if (c == '\'') { buf.append("''"); } else { buf.append(c); } } String rv = buf.toString(); return rv; } catch (Exception e) { M_log.warn("Validator.escapeSql: " + e, e); return ""; } } /** * @return a DocumentBuilder object for XML parsing. */ private static DocumentBuilder getDocumentBuilder() throws ParserConfigurationException { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); return dbf.newDocumentBuilder(); } }