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Xerces2 is the next generation of high performance, fully compliant XML parsers in the Apache Xerces family.
This new version of Xerces introduces the Xerces Native Interface (XNI), a complete framework for building
parser components and configurations that is extremely modular and easy to program. The Apache Xerces2 parser is
the reference implementation of XNI but other parser components, configurations, and parsers can be written
using the Xerces Native Interface. For complete design and implementation documents, refer to the XNI Manual.
Xerces2 is a fully conforming XML Schema 1.0 processor. A partial experimental implementation of the XML Schema
1.1 Structures and Datatypes Working Drafts (December 2009) and an experimental implementation of the XML Schema
Definition Language (XSD): Component Designators (SCD) Candidate Recommendation (January 2010) are provided for
evaluation. For more information, refer to the XML Schema page. Xerces2 also provides a complete implementation
of the Document Object Model Level 3 Core and Load/Save W3C Recommendations and provides a complete
implementation of the XML Inclusions (XInclude) W3C Recommendation. It also provides support for OASIS XML
Catalogs v1.1. Xerces2 is able to parse documents written according to the XML 1.1 Recommendation, except that
it does not yet provide an option to enable normalization checking as described in section 2.13 of this
specification. It also handles namespaces according to the XML Namespaces 1.1 Recommendation, and will correctly
serialize XML 1.1 documents if the DOM level 3 load/save APIs are in use.
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// $Id: XPathFactoryFinder.java 670432 2008-06-23 02:02:08Z mrglavas $
package javax.xml.xpath;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Properties;
import javax.xml.validation.SchemaFactory;
/**
* Implementation of {@link XPathFactory#newInstance(String)}.
*
* @author Kohsuke Kawaguchi
* @version $Revision: 670432 $, $Date: 2008-06-22 22:02:08 -0400 (Sun, 22 Jun 2008) $
* @since 1.5
*/
final class XPathFactoryFinder {
/** debug support code. */
private static boolean debug = false;
/**
* Default columns per line.
*/
private static final int DEFAULT_LINE_LENGTH = 80;
static {
// Use try/catch block to support applets
try {
String val = SecuritySupport.getSystemProperty("jaxp.debug");
// Allow simply setting the prop to turn on debug
debug = val != null && (! "false".equals(val));
} catch (Exception _) {
debug = false;
}
}
/**
* Cache properties for performance.
*/
private static Properties cacheProps = new Properties();
/**
* First time requires initialization overhead.
*/
private static boolean firstTime = true;
/**
* Conditional debug printing.
*
* @param msg to print
*/
private static void debugPrintln(String msg) {
if (debug) {
System.err.println("JAXP: " + msg);
}
}
/**
* ClassLoader to use to find SchemaFactory.
*/
private final ClassLoader classLoader;
/**
* Constructor that specifies ClassLoader to use
* to find SchemaFactory.
*
* @param loader
* to be used to load resource, {@link SchemaFactory}, and
* {@link SchemaFactoryLoader} implementations during
* the resolution process.
* If this parameter is null, the default system class loader
* will be used.
*/
public XPathFactoryFinder(ClassLoader loader) {
this.classLoader = loader;
if( debug ) {
debugDisplayClassLoader();
}
}
private void debugDisplayClassLoader() {
try {
if( classLoader == SecuritySupport.getContextClassLoader() ) {
debugPrintln("using thread context class loader ("+classLoader+") for search");
return;
}
}
// The VM ran out of memory or there was some other serious problem. Re-throw.
catch (VirtualMachineError vme) {
throw vme;
}
// ThreadDeath should always be re-thrown
catch (ThreadDeath td) {
throw td;
}
catch (Throwable _) {
; // getContextClassLoader() undefined in JDK1.1
}
if( classLoader==ClassLoader.getSystemClassLoader() ) {
debugPrintln("using system class loader ("+classLoader+") for search");
return;
}
debugPrintln("using class loader ("+classLoader+") for search");
}
/**
* Creates a new {@link XPathFactory} object for the specified
* schema language.
*
* @param uri
* Identifies the underlying object model.
*
* @return null if the callee fails to create one.
*
* @throws NullPointerException
* If the parameter is null.
*/
public XPathFactory newFactory(String uri) {
if(uri==null) throw new NullPointerException();
XPathFactory f = _newFactory(uri);
if (debug) {
if (f != null) {
debugPrintln("factory '" + f.getClass().getName() + "' was found for " + uri);
} else {
debugPrintln("unable to find a factory for " + uri);
}
}
return f;
}
/**
* Lookup a {@link XPathFactory} for the given object model.
*
* @param uri identifies the object model.
*
* @return {@link XPathFactory} for the given object model.
*/
private XPathFactory _newFactory(String uri) {
XPathFactory xpf;
String propertyName = SERVICE_CLASS.getName() + ":" + uri;
// system property look up
try {
if (debug) debugPrintln("Looking up system property '"+propertyName+"'" );
String r = SecuritySupport.getSystemProperty(propertyName);
if (r != null && r.length() > 0) {
if (debug) debugPrintln("The value is '"+r+"'");
xpf = createInstance(r);
if(xpf!=null) return xpf;
}
else if (debug) {
debugPrintln("The property is undefined.");
}
}
// The VM ran out of memory or there was some other serious problem. Re-throw.
catch (VirtualMachineError vme) {
throw vme;
}
// ThreadDeath should always be re-thrown
catch (ThreadDeath td) {
throw td;
}
catch (Throwable t) {
if( debug ) {
debugPrintln("failed to look up system property '"+propertyName+"'" );
t.printStackTrace();
}
}
String javah = SecuritySupport.getSystemProperty( "java.home" );
String configFile = javah + File.separator +
"lib" + File.separator + "jaxp.properties";
String factoryClassName = null ;
// try to read from $java.home/lib/jaxp.properties
try {
if(firstTime){
synchronized(cacheProps){
if(firstTime){
File f=new File( configFile );
firstTime = false;
if(SecuritySupport.doesFileExist(f)){
if (debug) debugPrintln("Read properties file " + f);
cacheProps.load(SecuritySupport.getFileInputStream(f));
}
}
}
}
factoryClassName = cacheProps.getProperty(propertyName);
if (debug) debugPrintln("found " + factoryClassName + " in $java.home/jaxp.properties");
if (factoryClassName != null) {
xpf = createInstance(factoryClassName);
if(xpf != null){
return xpf;
}
}
} catch (Exception ex) {
if (debug) {
ex.printStackTrace();
}
}
// try META-INF/services files
Iterator sitr = createServiceFileIterator();
while(sitr.hasNext()) {
URL resource = (URL)sitr.next();
if (debug) debugPrintln("looking into " + resource);
try {
xpf = loadFromServicesFile(uri, resource.toExternalForm(), SecuritySupport.getURLInputStream(resource));
if(xpf!=null) return xpf;
} catch(IOException e) {
if( debug ) {
debugPrintln("failed to read "+resource);
e.printStackTrace();
}
}
}
// platform default
if(uri.equals(XPathFactory.DEFAULT_OBJECT_MODEL_URI)) {
if (debug) debugPrintln("attempting to use the platform default W3C DOM XPath lib");
return createInstance("org.apache.xpath.jaxp.XPathFactoryImpl");
}
if (debug) debugPrintln("all things were tried, but none was found. bailing out.");
return null;
}
/**
* Creates an instance of the specified and returns it.
*
* @param className
* fully qualified class name to be instanciated.
*
* @return null
* if it fails. Error messages will be printed by this method.
*/
XPathFactory createInstance( String className ) {
try {
if (debug) debugPrintln("instanciating "+className);
Class clazz;
if( classLoader!=null )
clazz = classLoader.loadClass(className);
else
clazz = Class.forName(className);
if(debug) debugPrintln("loaded it from "+which(clazz));
Object o = clazz.newInstance();
if( o instanceof XPathFactory )
return (XPathFactory)o;
if (debug) debugPrintln(className+" is not assignable to "+SERVICE_CLASS.getName());
}
// The VM ran out of memory or there was some other serious problem. Re-throw.
catch (VirtualMachineError vme) {
throw vme;
}
// ThreadDeath should always be re-thrown
catch (ThreadDeath td) {
throw td;
}
catch (Throwable t) {
if (debug) {
debugPrintln("failed to instanciate "+className);
t.printStackTrace();
}
}
return null;
}
/** Iterator that lazily computes one value and returns it. */
private static abstract class SingleIterator implements Iterator {
private boolean seen = false;
public final void remove() { throw new UnsupportedOperationException(); }
public final boolean hasNext() { return !seen; }
public final Object next() {
if(seen) throw new NoSuchElementException();
seen = true;
return value();
}
protected abstract Object value();
}
/** Searches for a XPathFactory for a given uri in a META-INF/services file. */
private XPathFactory loadFromServicesFile(String uri, String resourceName, InputStream in) {
if (debug) debugPrintln("Reading " + resourceName );
BufferedReader rd;
try {
rd = new BufferedReader(new InputStreamReader(in, "UTF-8"), DEFAULT_LINE_LENGTH);
} catch (java.io.UnsupportedEncodingException e) {
rd = new BufferedReader(new InputStreamReader(in), DEFAULT_LINE_LENGTH);
}
String factoryClassName = null;
XPathFactory resultFactory = null;
// See spec for provider-configuration files: http://java.sun.com/j2se/1.5.0/docs/guide/jar/jar.html#Provider%20Configuration%20File
while (true) {
try {
factoryClassName = rd.readLine();
} catch (IOException x) {
// No provider found
break;
}
if (factoryClassName != null) {
// Ignore comments in the provider-configuration file
int hashIndex = factoryClassName.indexOf('#');
if (hashIndex != -1) {
factoryClassName = factoryClassName.substring(0, hashIndex);
}
// Ignore leading and trailing whitespace
factoryClassName = factoryClassName.trim();
// If there's no text left or if this was a blank line, go to the next one.
if (factoryClassName.length() == 0) {
continue;
}
try {
// Found the right XPathFactory if its isObjectModelSupported(String uri) method returns true.
XPathFactory foundFactory = (XPathFactory) createInstance(factoryClassName);
if (foundFactory.isObjectModelSupported(uri)) {
resultFactory = foundFactory;
break;
}
}
catch (Exception e) {}
}
else {
break;
}
}
try {
// try to close the reader.
rd.close();
}
// Ignore the exception.
catch (IOException exc) {}
return resultFactory;
}
/**
* Returns an {@link Iterator} that enumerates all
* the META-INF/services files that we care.
*/
private Iterator createServiceFileIterator() {
if (classLoader == null) {
return new SingleIterator() {
protected Object value() {
ClassLoader classLoader = XPathFactoryFinder.class.getClassLoader();
return SecuritySupport.getResourceAsURL(classLoader, SERVICE_ID);
//return (ClassLoader.getSystemResource( SERVICE_ID ));
}
};
} else {
try {
//final Enumeration e = classLoader.getResources(SERVICE_ID);
final Enumeration e = SecuritySupport.getResources(classLoader, SERVICE_ID);
if (debug && !e.hasMoreElements()) {
debugPrintln("no "+SERVICE_ID+" file was found");
}
// wrap it into an Iterator.
return new Iterator() {
public void remove() {
throw new UnsupportedOperationException();
}
public boolean hasNext() {
return e.hasMoreElements();
}
public Object next() {
return e.nextElement();
}
};
} catch (IOException e) {
if (debug) {
debugPrintln("failed to enumerate resources "+SERVICE_ID);
e.printStackTrace();
}
return new ArrayList().iterator(); // empty iterator
}
}
}
private static final Class SERVICE_CLASS = XPathFactory.class;
private static final String SERVICE_ID = "META-INF/services/" + SERVICE_CLASS.getName();
private static String which( Class clazz ) {
return which( clazz.getName(), clazz.getClassLoader() );
}
/**
* Search the specified classloader for the given classname.
*
* @param classname the fully qualified name of the class to search for
* @param loader the classloader to search
*
* @return the source location of the resource, or null if it wasn't found
*/
private static String which(String classname, ClassLoader loader) {
String classnameAsResource = classname.replace('.', '/') + ".class";
if( loader==null ) loader = ClassLoader.getSystemClassLoader();
//URL it = loader.getResource(classnameAsResource);
URL it = SecuritySupport.getResourceAsURL(loader, classnameAsResource);
if (it != null) {
return it.toString();
} else {
return null;
}
}
}