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);
}
}
/**
* Attempt to create an XML reader from a class name.
*
* <p>Given a class name, this method attempts to load and instantiate the class as an XML reader.
*
* <p>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(NewInstance.getClassLoader(), className);
}
/**
* 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:
*
* <ul>
* <li>If the system property <code>org.xml.sax.driver</code> has a value, that is used as an
* XMLReader class name.
* <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>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>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.)
* </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>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.
*
* @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 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) {
if (!_jarread) {
final ClassLoader loader1 = loader;
_jarread = true;
_clsFromJar =
(String)
AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
String clsName = null;
try {
String service = "META-INF/services/" + property;
InputStream in;
BufferedReader reader;
if (loader1 == null) in = ClassLoader.getSystemResourceAsStream(service);
else in = loader1.getResourceAsStream(service);
if (in != null) {
reader = new BufferedReader(new InputStreamReader(in, "UTF8"));
clsName = reader.readLine();
in.close();
}
} catch (Exception e) {
}
return clsName;
}
});
}
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(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?");
}
}
