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XMLReaderFactory.javaAPI DocJava SE 6 API6981Tue Jun 10 00:27:38 BST 2008org.xml.sax.helpers

XMLReaderFactory

public final class XMLReaderFactory extends Object
Factory for creating an XML reader.
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 org.xml.sax.driver so those configuration mechanisms would see it.

since
SAX 2.0
author
David Megginson, David Brownell
version
2.0.1 (sax2r2)

Fields Summary
private static final String
property
Constructors Summary
private XMLReaderFactory()
Private constructor.

This constructor prevents the class from being instantiated.
Methods Summary
public static org.xml.sax.XMLReadercreateXMLReader()
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:

  • If the system property org.xml.sax.driver has a value, that is used as an XMLReader class name.
  • The JAR "Services API" is used to look for a class name in the META-INF/services/org.xml.sax.driver file in jarfiles available to the runtime.
  • 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.
  • 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 org.xml.sax.parser system property will often be usable.)

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)


                                                                                                                                                                                                                                                                         
        
	 
    
	String		className = null;
	ClassLoader	loader = NewInstance.getClassLoader ();
	
	// 1. try the JVM-instance-wide system property
	try { className = System.getProperty (property); }
	catch (RuntimeException e) { /* normally fails for applets */ }

	// 2. if that fails, try META-INF/services/
	if (className == null) {
	    try {
		String		service = "META-INF/services/" + property;
		InputStream	in;
		BufferedReader	reader;

		if (loader == null)
		    in = ClassLoader.getSystemResourceAsStream (service);
		else
		    in = loader.getResourceAsStream (service);

		if (in != null) {
		    reader = new BufferedReader (
			    new InputStreamReader (in, "UTF8"));
		    className = reader.readLine ();
		    in.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...
            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 (Exception e) {
	    throw new SAXException ("Can't create default XMLReader; "
		    + "is system property org.xml.sax.driver set?");
	}
public static org.xml.sax.XMLReadercreateXMLReader(java.lang.String className)
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()

	return loadClass (NewInstance.getClassLoader (), className);
private static org.xml.sax.XMLReaderloadClass(java.lang.ClassLoader loader, java.lang.String className)

	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);
	}