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137 lines
4.2 KiB
Java
137 lines
4.2 KiB
Java
// XMLReaderFactory.java - factory for creating a new reader.
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// Written by David Megginson, sax@megginson.com
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// NO WARRANTY! This class is in the Public Domain.
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// $Id: XMLReaderFactory.java,v 1.1 2000/10/02 02:43:20 sboag Exp $
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package org.xml.sax.helpers;
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import org.xml.sax.Parser;
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import org.xml.sax.XMLReader;
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import org.xml.sax.SAXException;
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/**
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* Factory for creating an XML reader.
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*
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* <blockquote>
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* <em>This module, both source code and documentation, is in the
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* Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
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* </blockquote>
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*
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* <p>This class contains static methods for creating an XML reader
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* from an explicit class name, or for creating an XML reader based
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* on the value of the <code>org.xml.sax.driver</code> system
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* property:</p>
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*
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* <pre>
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* try {
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* XMLReader myReader = XMLReaderFactory.createXMLReader();
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* } catch (SAXException e) {
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* System.err.println(e.getMessage());
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* }
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* </pre>
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*
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* <p>Note that these methods will not be usable in environments where
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* system properties are not accessible or where the application or
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* applet is not permitted to load classes dynamically.</p>
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*
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* <p><strong>Note to implementors:</strong> SAX implementations in specialized
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* environments may replace this class with a different one optimized for the
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* environment, as long as its method signatures remain the same.</p>
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*
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* @since SAX 2.0
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* @author David Megginson,
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* <a href="mailto:sax@megginson.com">sax@megginson.com</a>
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* @version 2.0
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* @see org.xml.sax.XMLReader
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*/
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final public class XMLReaderFactory
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{
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/**
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* Private constructor.
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*
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* <p>This constructor prevents the class from being instantiated.</p>
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*/
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private XMLReaderFactory ()
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{
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}
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/**
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* Attempt to create an XML reader from a system property.
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*
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* <p>This method uses the value of the system property
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* "org.xml.sax.driver" as the full name of a Java class
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* and tries to instantiate that class as a SAX2
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* XMLReader.</p>
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*
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* <p>Note that many Java interpreters allow system properties
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* to be specified on the command line.</p>
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*
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* @return A new XMLReader.
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* @exception org.xml.sax.SAXException If the value of the
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* "org.xml.sax.driver" system property is null,
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* or if the class cannot be loaded and instantiated.
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* @see #createXMLReader(java.lang.String)
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*/
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public static XMLReader createXMLReader ()
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throws SAXException
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{
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String className = System.getProperty("org.xml.sax.driver");
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if (className == null) {
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Parser parser;
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try {
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parser = ParserFactory.makeParser();
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} catch (Exception e) {
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parser = null;
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}
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if (parser == null) {
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throw new
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SAXException("System property org.xml.sax.driver not specified");
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} else {
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return new ParserAdapter(parser);
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}
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} else {
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return createXMLReader(className);
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}
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}
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/**
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* Attempt to create an XML reader from a class name.
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*
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* <p>Given a class name, this method attempts to load
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* and instantiate the class as an XML reader.</p>
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*
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* @return A new XML reader.
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* @exception org.xml.sax.SAXException If the class cannot be
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* loaded, instantiated, and cast to XMLReader.
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* @see #createXMLReader()
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*/
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public static XMLReader createXMLReader (String className)
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throws SAXException
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{
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try {
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return (XMLReader)(Class.forName(className).newInstance());
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} catch (ClassNotFoundException e1) {
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throw new SAXException("SAX2 driver class " + className +
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" not found", e1);
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} catch (IllegalAccessException e2) {
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throw new SAXException("SAX2 driver class " + className +
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" found but cannot be loaded", e2);
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} catch (InstantiationException e3) {
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throw new SAXException("SAX2 driver class " + className +
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" loaded but cannot be instantiated (no empty public constructor?)",
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e3);
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} catch (ClassCastException e4) {
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throw new SAXException("SAX2 driver class " + className +
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" does not implement XMLReader", e4);
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}
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}
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}
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// end of XMLReaderFactory.java
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