/*
* 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:<p/> <ul>
*
* <li>If the system property <code>org.xml.sax.driver</code>
* has a value, that is used as an XMLReader class name. </li>
*
* <li>The JAR "Services API" is used to look for a class name
* in the <em>META-INF/services/org.xml.sax.driver</em> file in
* jarfiles available to the runtime.</li>
*
* <li> SAX parser distributions are strongly encouraged to provide
* a default XMLReader class name that will take effect only when
* previous options (on this list) are not successful.</li>
*
* <li>Finally, if {@link ParserFactory#makeParser()} can
* return a system default SAX1 parser, that parser is wrapped in
* a {@link ParserAdapter}. (This is a migration aid for SAX1
* environments, where the <code>org.xml.sax.parser</code> system
* property will often be usable.) </li>
*
* </ul>
*
* <p> In environments such as small embedded systems, which can not
* support that flexibility, other mechanisms to determine the default
* may be used. </p>
*
* <p>Note that many Java environments allow system properties to be
* initialized on a command line. This means that <em>in most cases</em>
* 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.
* </p>
*
* @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;
java.lang.ClassLoader loader = NewInstance.getClassLoader();
// 1. try the JVM-instance-wide system property
try { className = java.lang.SystemJ.getProperty(property); }
catch (java.lang.RuntimeException e) { /* normally fails for applets */ }
// 2. if that fails, try META-INF/services/
if (className == null)
{
try {
String service = "META-INF/services/" + property;
java.io.InputStream input;
java.io.BufferedReader reader;
if (loader == null)
{
input = java.lang.ClassLoader.getSystemResourceAsStream(service);
}
else
{
input = loader.getResourceAsStream(service);
}
if (input != null)
{
reader = new java.io.BufferedReader(
new java.io.InputStreamReader(input, "UTF8"));
className = reader.readLine();
input.close();
}
} catch (Exception e) {
}
}
// 3. Distro-specific fallback
if (className == null)
{
// BEGIN DISTRIBUTION-SPECIFIC
// EXAMPLE:
// className = "com.example.sax.XmlReader";
// or a $JAVA_HOME/jre/lib/*properties setting...
//Take a look in Java 7 shows: 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(loader, className));
}
// 4. panic -- adapt any SAX1 parser
try {
return(new ParserAdapter(ParserFactory.makeParser()));
} catch (java.lang.Exception e) {
throw new SAXException("Can't create default XMLReader; "
+ "is system property org.xml.sax.driver set?");
}
}
