* This module, both source code and documentation, is in the * Public Domain, and comes with NO WARRANTY. * See http://www.saxproject.org * for further information. ** *
This class contains static methods for creating an XML reader * from an explicit class name, or based on runtime defaults: * *
* try {
* XMLReader myReader = XMLReaderFactory.createXMLReader();
* } catch (SAXException e) {
* System.err.println(e.getMessage());
* }
*
*
* Note to Distributions bundled with parsers: * You should modify the implementation of the no-arguments * createXMLReader to handle cases where the external * configuration mechanisms aren't set up. That method should do its * best to return a parser when one is in the class path, even when * nothing bound its class name to {@code org.xml.sax.driver} so * those configuration mechanisms would see it. * * @since 1.4, SAX 2.0 * @author David Megginson, David Brownell * @version 2.0.1 (sax2r2) */ final public class XMLReaderFactory { /** * Private constructor. * *
This constructor prevents the class from being instantiated. */ private XMLReaderFactory () { } private static final String property = "org.xml.sax.driver"; private static SecuritySupport ss = new SecuritySupport(); private static String _clsFromJar = null; private static boolean _jarread = false; /** * Attempt to create an XMLReader from system defaults. * In environments which can support it, the name of the XMLReader * class is determined by trying each these options in order, and * using the first one which succeeds: *
In environments such as small embedded systems, which can not * support that flexibility, other mechanisms to determine the default * may be used. * *
Note that many Java environments allow system properties to be * initialized on a command line. This means that in most cases * setting a good value for that property ensures that calls to this * method will succeed, except when security policies intervene. * This will also maximize application portability to older SAX * environments, with less robust implementations of this method. * * * @return A new XMLReader. * @exception org.xml.sax.SAXException If no default XMLReader class * can be identified and instantiated. * @see #createXMLReader(java.lang.String) */ public static XMLReader createXMLReader () throws SAXException { String className = null; ClassLoader cl = ss.getContextClassLoader(); // 1. try the JVM-instance-wide system property try { className = ss.getSystemProperty(property); } catch (RuntimeException e) { /* continue searching */ } // 2. if that fails, try META-INF/services/ if (className == null) { if (!_jarread) { _jarread = true; String service = "META-INF/services/" + property; InputStream in; BufferedReader reader; try { if (cl != null) { in = ss.getResourceAsStream(cl, service); // If no provider found then try the current ClassLoader if (in == null) { cl = null; in = ss.getResourceAsStream(cl, service); } } else { // No Context ClassLoader, try the current ClassLoader in = ss.getResourceAsStream(cl, service); } if (in != null) { reader = new BufferedReader (new InputStreamReader (in, "UTF8")); _clsFromJar = reader.readLine (); in.close (); } } catch (Exception e) { } } className = _clsFromJar; } // 3. Distro-specific fallback if (className == null) { // BEGIN DISTRIBUTION-SPECIFIC // EXAMPLE: // className = "com.example.sax.XmlReader"; // or a $JAVA_HOME/jre/lib/*properties setting... className = "com.sun.org.apache.xerces.internal.parsers.SAXParser"; // END DISTRIBUTION-SPECIFIC } // do we know the XMLReader implementation class yet? if (className != null) return loadClass (cl, className); // 4. panic -- adapt any SAX1 parser try { return new ParserAdapter (ParserFactory.makeParser ()); } catch (Exception e) { throw new SAXException ("Can't create default XMLReader; " + "is system property org.xml.sax.driver set?"); } } /** * Attempt to create an XML reader from a class name. * *
Given a class name, this method attempts to load * and instantiate the class as an XML reader. * *
Note that this method will not be usable in environments where * the caller (perhaps an applet) is not permitted to load classes * dynamically. * * @return A new XML reader. * @exception org.xml.sax.SAXException If the class cannot be * loaded, instantiated, and cast to XMLReader. * @see #createXMLReader() */ public static XMLReader createXMLReader (String className) throws SAXException { return loadClass (ss.getContextClassLoader(), className); } private static XMLReader loadClass (ClassLoader loader, String className) throws SAXException { try { return (XMLReader) NewInstance.newInstance (loader, className); } catch (ClassNotFoundException e1) { throw new SAXException("SAX2 driver class " + className + " not found", e1); } catch (IllegalAccessException e2) { throw new SAXException("SAX2 driver class " + className + " found but cannot be loaded", e2); } catch (InstantiationException e3) { throw new SAXException("SAX2 driver class " + className + " loaded but cannot be instantiated (no empty public constructor?)", e3); } catch (ClassCastException e4) { throw new SAXException("SAX2 driver class " + className + " does not implement XMLReader", e4); } } }