jaxp-api-1.4/src/main/java/javax/xml/xpath/XPathFactoryFinder.java - servicemix-specs - Git at Google

 /*
  * 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 446598 2006-09-15 12:55:40Z jeremias $

 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 <a href="Kohsuke.Kawaguchi@Sun.com">Kohsuke Kawaguchi</a>
  * @version $Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
  * @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;
         }
     }

     /**
      * <p>Cache properties for performance.</p>
      */
 	private static Properties cacheProps = new Properties();

 	/**
 	 * <p>First time requires initialization overhead.</p>
 	 */
 	private static boolean firstTime = true;

     /**
      * <p>Conditional debug printing.</p>
      *
      * @param msg to print
      */
     private static void debugPrintln(String msg) {
         if (debug) {
             System.err.println("JAXP: " + msg);
         }
     }

     /**
      * <p><code>ClassLoader</code> to use to find <code>SchemaFactory</code>.</p>
      */
     private final ClassLoader classLoader;

     /**
      * <p>Constructor that specifies <code>ClassLoader</code> to use
      * to find <code>SchemaFactory</code>.</p>
      *
      * @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;
             }
         } 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");
     }

     /**
      * <p>Creates a new {@link XPathFactory} object for the specified
      * schema language.</p>
      *
      * @param uri
      *       Identifies the underlying object model.
      *
      * @return <code>null</code> 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;
     }

     /**
      * <p>Lookup a {@link XPathFactory} for the given object model.</p>
      *
      * @param uri identifies the object model.
      *
      * @return {@link XPathFactory} for the given object model.
      */
     private XPathFactory _newFactory(String uri) {
         XPathFactory sf;

         String propertyName = SERVICE_CLASS.getName() + ":" + uri;

         try {
             // If we are deployed into an OSGi environment, leverage it
             Class spiClass = org.apache.servicemix.specs.locator.OsgiLocator.locate(SERVICE_CLASS);
             if (spiClass != null) {
                 return (XPathFactory) spiClass.newInstance();
             }
         } catch (Throwable e) {
         }

         // system property look up
         try {
             if (debug) debugPrintln("Looking up system property '"+propertyName+"'" );
             String r = SecuritySupport.getSystemProperty(propertyName);
             if(r!=null) {
                 if (debug) debugPrintln("The value is '"+r+"'");
                 sf = createInstance(r);
                 if(sf!=null)    return sf;
             }
             else if (debug) {
                 debugPrintln("The property is undefined.");
             }
         } 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) {
                 sf = createInstance(factoryClassName);
                 if(sf != null){
                     return sf;
                 }
             }
         } 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 {
                 sf = loadFromServicesFile(uri, resource.toExternalForm(), SecuritySupport.getURLInputStream(resource));
                 if(sf!=null)    return sf;
             } 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");
             XPathFactory f = createInstance("com.sun.org.apache.xpath.internal.jaxp.XPathFactoryImpl");
             if (f == null) {
                 //IBM JDK
                 f = createInstance("org.apache.xpath.jaxp.XPathFactoryImpl");
             }
             return f;
         }

         if (debug) debugPrintln("all things were tried, but none was found. bailing out.");
         return null;
     }

     /**
      * <p>Creates an instance of the specified and returns it.</p>
      *
      * @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());
         } 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() );
     }

     /**
      * <p>Search the specified classloader for the given classname.</p>
      *
      * @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;
         }
     }
 }
	/*
	* 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 446598 2006-09-15 12:55:40Z jeremias $

	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 <a href="Kohsuke.Kawaguchi@Sun.com">Kohsuke Kawaguchi</a>
	* @version $Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
	* @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;
	}
	}

	/**
	* <p>Cache properties for performance.</p>
	*/
	private static Properties cacheProps = new Properties();

	/**
	* <p>First time requires initialization overhead.</p>
	*/
	private static boolean firstTime = true;

	/**
	* <p>Conditional debug printing.</p>
	*
	* @param msg to print
	*/
	private static void debugPrintln(String msg) {
	if (debug) {
	System.err.println("JAXP: " + msg);
	}
	}

	/**
	* <p><code>ClassLoader</code> to use to find <code>SchemaFactory</code>.</p>
	*/
	private final ClassLoader classLoader;

	/**
	* <p>Constructor that specifies <code>ClassLoader</code> to use
	* to find <code>SchemaFactory</code>.</p>
	*
	* @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;
	}
	} 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");
	}

	/**
	* <p>Creates a new {@link XPathFactory} object for the specified
	* schema language.</p>
	*
	* @param uri
	* Identifies the underlying object model.
	*
	* @return <code>null</code> 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;
	}

	/**
	* <p>Lookup a {@link XPathFactory} for the given object model.</p>
	*
	* @param uri identifies the object model.
	*
	* @return {@link XPathFactory} for the given object model.
	*/
	private XPathFactory _newFactory(String uri) {
	XPathFactory sf;

	String propertyName = SERVICE_CLASS.getName() + ":" + uri;

	try {
	// If we are deployed into an OSGi environment, leverage it
	Class spiClass = org.apache.servicemix.specs.locator.OsgiLocator.locate(SERVICE_CLASS);
	if (spiClass != null) {
	return (XPathFactory) spiClass.newInstance();
	}
	} catch (Throwable e) {
	}

	// system property look up
	try {
	if (debug) debugPrintln("Looking up system property '"+propertyName+"'" );
	String r = SecuritySupport.getSystemProperty(propertyName);
	if(r!=null) {
	if (debug) debugPrintln("The value is '"+r+"'");
	sf = createInstance(r);
	if(sf!=null) return sf;
	}
	else if (debug) {
	debugPrintln("The property is undefined.");
	}
	} 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) {
	sf = createInstance(factoryClassName);
	if(sf != null){
	return sf;
	}
	}
	} 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 {
	sf = loadFromServicesFile(uri, resource.toExternalForm(), SecuritySupport.getURLInputStream(resource));
	if(sf!=null) return sf;
	} 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");
	XPathFactory f = createInstance("com.sun.org.apache.xpath.internal.jaxp.XPathFactoryImpl");
	if (f == null) {
	//IBM JDK
	f = createInstance("org.apache.xpath.jaxp.XPathFactoryImpl");
	}
	return f;
	}

	if (debug) debugPrintln("all things were tried, but none was found. bailing out.");
	return null;
	}

	/**
	* <p>Creates an instance of the specified and returns it.</p>
	*
	* @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());
	} 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() );
	}

	/**
	* <p>Search the specified classloader for the given classname.</p>
	*
	* @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;
	}
	}
	}