VFS-2.0-RC1/core/src/main/java/org/apache/commons/vfs/impl/StandardFileSystemManager.java - commons-vfs - 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.
  */
 package org.apache.commons.vfs.impl;

 import java.io.IOException;
 import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Enumeration;

 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
 import javax.xml.parsers.ParserConfigurationException;

 import org.apache.commons.vfs.FileSystemException;
 import org.apache.commons.vfs.VfsLog;
 import org.apache.commons.vfs.operations.FileOperationProvider;
 import org.apache.commons.vfs.provider.FileProvider;
 import org.apache.commons.vfs.util.Messages;
 import org.w3c.dom.Element;
 import org.w3c.dom.NodeList;

 /**
  * A {@link org.apache.commons.vfs.FileSystemManager} that configures itself
  * from an XML (Default: providers.xml) configuration file.<br>
  * Certain providers are only loaded and available if the dependend library is in your
  * classpath. You have to configure your debugging facility to log "debug" messages to see
  * if a provider was skipped due to "unresolved externals".
  *
  * @author <a href="mailto:adammurdoch@apache.org">Adam Murdoch</a>
  * @version $Revision$ $Date$
  */
 public class StandardFileSystemManager
     extends DefaultFileSystemManager
 {
     private static final String CONFIG_RESOURCE = "providers.xml";
     private static final String PLUGIN_CONFIG_RESOURCE = "META-INF/vfs-providers.xml";

     private URL configUri;
     private ClassLoader classLoader;

     /**
      * Sets the configuration file for this manager.
      * @param configUri The URI for this manager.
      */
     public void setConfiguration(final String configUri)
     {
         try
         {
             setConfiguration(new URL(configUri));
         }
         catch (MalformedURLException e)
         {
             getLogger().warn(e.getLocalizedMessage(), e);
         }
     }

     /**
      * Sets the configuration file for this manager.
      * @param configUri The URI forthis manager.
      */
     public void setConfiguration(final URL configUri)
     {
         this.configUri = configUri;
     }

     /**
      * Sets the ClassLoader to use to load the providers.  Default is to
      * use the ClassLoader that loaded this class.
      * @param classLoader The ClassLoader.
      */
     public void setClassLoader(final ClassLoader classLoader)
     {
         this.classLoader = classLoader;
     }

     /**
      * Initializes this manager.  Adds the providers and replicator.
      * @throws FileSystemException if an error occurs.
      */
     public void init() throws FileSystemException
     {
         // Set the replicator and temporary file store (use the same component)
         final DefaultFileReplicator replicator = createDefaultFileReplicator();
         setReplicator(new PrivilegedFileReplicator(replicator));
         setTemporaryFileStore(replicator);

         /* replaced by findClassLoader
         if (classLoader == null)
         {
             // Use default classloader
             classLoader = getClass().getClassLoader();
         }
         */

         if (configUri == null)
         {
             // Use default config
             final URL url = getClass().getResource(CONFIG_RESOURCE);
             if (url == null)
             {
                 throw new FileSystemException("vfs.impl/find-config-file.error", CONFIG_RESOURCE);
             }
             configUri = url;
         }

         // Configure
         configure(configUri);

         // Configure Plugins
         configurePlugins();

         // Initialise super-class
         super.init();
     }

     /**
      * Scans the classpath to find any droped plugin.<br />
      * The plugin-description has to be in /META-INF/vfs-providers.xml
      * @throws FileSystemException if an error occurs.
      */
     protected void configurePlugins() throws FileSystemException
     {
         ClassLoader cl = findClassLoader();

         Enumeration enumResources;
         try
         {
             enumResources = cl.getResources(PLUGIN_CONFIG_RESOURCE);
         }
         catch (IOException e)
         {
             throw new FileSystemException(e);
         }

         while (enumResources.hasMoreElements())
         {
             URL url = (URL) enumResources.nextElement();
             configure(url);
         }
     }

     private ClassLoader findClassLoader()
     {
         if (classLoader != null)
         {
             return classLoader;
         }

         ClassLoader cl = Thread.currentThread().getContextClassLoader();
         if (cl == null)
         {
             cl = getClass().getClassLoader();
         }

         return cl;
     }

     protected DefaultFileReplicator createDefaultFileReplicator()
     {
         return new DefaultFileReplicator();
     }

     /**
      * Configures this manager from an XML configuration file.
      * @param configUri The URI of the configuration.
      * @throws FileSystemException if an error occus.
      */
     private void configure(final URL configUri) throws FileSystemException
     {
         InputStream configStream = null;
         try
         {
             // Load up the config
             // TODO - validate
             final DocumentBuilder builder = createDocumentBuilder();
             configStream = configUri.openStream();
             final Element config = builder.parse(configStream).getDocumentElement();

             configure(config);
         }
         catch (final Exception e)
         {
             throw new FileSystemException("vfs.impl/load-config.error", configUri.toString(), e);
         }
         finally
         {
             if (configStream != null)
             {
                 try
                 {
                     configStream.close();
                 }
                 catch (IOException e)
                 {
                     getLogger().warn(e.getLocalizedMessage(), e);
                 }
             }
         }
     }

     /**
      * Configures this manager from an XML configuration file.
      * @param configUri The URI of the configuration.
      * @param configStream An InputStream containing the configuration.
      * @throws FileSystemException if an error occurs.
      */
     private void configure(final String configUri, final InputStream configStream)
             throws FileSystemException
     {
         try
         {
             // Load up the config
             // TODO - validate
             final DocumentBuilder builder = createDocumentBuilder();
             final Element config = builder.parse(configStream).getDocumentElement();

             configure(config);

         }
         catch (final Exception e)
         {
             throw new FileSystemException("vfs.impl/load-config.error", configUri, e);
         }
     }

     /**
      * Configure and create a DocumentBuilder
      * @return A DocumentBuilder for the configuration.
      * @throws ParserConfigurationException if an error occurs.
      */
     private DocumentBuilder createDocumentBuilder() throws ParserConfigurationException
     {
         final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
         factory.setIgnoringElementContentWhitespace(true);
         factory.setIgnoringComments(true);
         factory.setExpandEntityReferences(true);
         return  factory.newDocumentBuilder();
     }

     /**
      * Configures this manager from an parsed XML configuration file
      * @param config The configuration Element.
      * @throws FileSystemException if an error occurs.
      */
     private void configure(final Element config) throws FileSystemException
     {
         // Add the providers
         final NodeList providers = config.getElementsByTagName("provider");
         final int count = providers.getLength();
         for (int i = 0; i < count; i++)
         {
             final Element provider = (Element) providers.item(i);
             addProvider(provider, false);
         }

         // Add the operation providers
         final NodeList operationProviders = config.getElementsByTagName("operationProvider");
         for (int i = 0; i < operationProviders.getLength(); i++)
         {
             final Element operationProvider = (Element) operationProviders.item(i);
             addOperationProvider(operationProvider);
         }

         // Add the default provider
         final NodeList defProviders = config.getElementsByTagName("default-provider");
         if (defProviders.getLength() > 0)
         {
             final Element provider = (Element) defProviders.item(0);
             addProvider(provider, true);
         }

         // Add the mime-type maps
         final NodeList mimeTypes = config.getElementsByTagName("mime-type-map");
         for (int i = 0; i < mimeTypes.getLength(); i++)
         {
             final Element map = (Element) mimeTypes.item(i);
             addMimeTypeMap(map);
         }

         // Add the extension maps
         final NodeList extensions = config.getElementsByTagName("extension-map");
         for (int i = 0; i < extensions.getLength(); i++)
         {
             final Element map = (Element) extensions.item(i);
             addExtensionMap(map);
         }
     }

     /**
      * Adds an extension map.
      * @param map containing the Elements.
      */
     private void addExtensionMap(final Element map)
     {
         final String extension = map.getAttribute("extension");
         final String scheme = map.getAttribute("scheme");
         if (scheme != null && scheme.length() > 0)
         {
             addExtensionMap(extension, scheme);
         }
     }

     /**
      * Adds a mime-type map.
      * @param map containing the Elements.
      */
     private void addMimeTypeMap(final Element map)
     {
         final String mimeType = map.getAttribute("mime-type");
         final String scheme = map.getAttribute("scheme");
         addMimeTypeMap(mimeType, scheme);
     }

     /**
      * Adds a provider from a provider definition.
      * @param providerDef the provider definition
      * @param isDefault true if the default should be used.
      * @throws FileSystemException if an error occurs.
      */
     private void addProvider(final Element providerDef, final boolean isDefault)
         throws FileSystemException
     {
         final String classname = providerDef.getAttribute("class-name");

         // Make sure all required schemes are available
         final String[] requiredSchemes = getRequiredSchemes(providerDef);
         for (int i = 0; i < requiredSchemes.length; i++)
         {
             final String requiredScheme = requiredSchemes[i];
             if (!hasProvider(requiredScheme))
             {
                 final String msg = Messages.getString("vfs.impl/skipping-provider-scheme.debug",
                     new String[]{classname, requiredScheme});
                 VfsLog.debug(getLogger(), getLogger(), msg);
                 return;
             }
         }

         // Make sure all required classes are in classpath
         final String[] requiredClasses = getRequiredClasses(providerDef);
         for (int i = 0; i < requiredClasses.length; i++)
         {
             final String requiredClass = requiredClasses[i];
             if (!findClass(requiredClass))
             {
                 final String msg = Messages.getString("vfs.impl/skipping-provider.debug",
                     new String[]{classname, requiredClass});
                 VfsLog.debug(getLogger(), getLogger(), msg);
                 return;
             }
         }

         // Create and register the provider
         final FileProvider provider = (FileProvider) createInstance(classname);
         final String[] schemas = getSchemas(providerDef);
         if (schemas.length > 0)
         {
             addProvider(schemas, provider);
         }

         // Set as default, if required
         if (isDefault)
         {
             setDefaultProvider(provider);
         }
     }

     /**
      * Adds a operationProvider from a operationProvider definition.
      */
     private void addOperationProvider(final Element providerDef) throws FileSystemException
     {
         final String classname = providerDef.getAttribute("class-name");

         // Attach only to available schemas
         final String[] schemas = getSchemas(providerDef);
         for (int i = 0; i < schemas.length; i++)
         {
             final String schema = schemas[i];
             if (hasProvider(schema))
             {
                 final FileOperationProvider operationProvider = (FileOperationProvider) createInstance(classname);
                 addOperationProvider(schema, operationProvider);
             }
         }
     }

     /**
      * Tests if a class is available.
      */
     private boolean findClass(final String className)
     {
         try
         {
             findClassLoader().loadClass(className);
             return true;
         }
         catch (final ClassNotFoundException e)
         {
             return false;
         }
     }

     /**
      * Extracts the required classes from a provider definition.
      */
     private String[] getRequiredClasses(final Element providerDef)
     {
         final ArrayList classes = new ArrayList();
         final NodeList deps = providerDef.getElementsByTagName("if-available");
         final int count = deps.getLength();
         for (int i = 0; i < count; i++)
         {
             final Element dep = (Element) deps.item(i);
             String className = dep.getAttribute("class-name");
             if (className != null && className.length() > 0)
             {
                 classes.add(className);
             }
         }
         return (String[]) classes.toArray(new String[classes.size()]);
     }

     /**
      * Extracts the required schemes from a provider definition.
      */
     private String[] getRequiredSchemes(final Element providerDef)
     {
         final ArrayList schemes = new ArrayList();
         final NodeList deps = providerDef.getElementsByTagName("if-available");
         final int count = deps.getLength();
         for (int i = 0; i < count; i++)
         {
             final Element dep = (Element) deps.item(i);
             String scheme = dep.getAttribute("scheme");
             if (scheme != null && scheme.length() > 0)
             {
                 schemes.add(scheme);
             }
         }
         return (String[]) schemes.toArray(new String[schemes.size()]);
     }

     /**
      * Extracts the schema names from a provider definition.
      */
     private String[] getSchemas(final Element provider)
     {
         final ArrayList schemas = new ArrayList();
         final NodeList schemaElements = provider.getElementsByTagName("scheme");
         final int count = schemaElements.getLength();
         for (int i = 0; i < count; i++)
         {
             final Element scheme = (Element) schemaElements.item(i);
             schemas.add(scheme.getAttribute("name"));
         }
         return (String[]) schemas.toArray(new String[schemas.size()]);
     }

     /**
      * Creates a provider.
      */
     private Object createInstance(final String className)
         throws FileSystemException
     {
         try
         {
             final Class clazz = findClassLoader().loadClass(className);
             return clazz.newInstance();
         }
         catch (final Exception e)
         {
             throw new FileSystemException("vfs.impl/create-provider.error", className, e);
         }
     }
 }
	/*
	* 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.
	*/
	package org.apache.commons.vfs.impl;

	import java.io.IOException;
	import java.io.InputStream;
	import java.net.MalformedURLException;
	import java.net.URL;
	import java.util.ArrayList;
	import java.util.Enumeration;

	import javax.xml.parsers.DocumentBuilder;
	import javax.xml.parsers.DocumentBuilderFactory;
	import javax.xml.parsers.ParserConfigurationException;

	import org.apache.commons.vfs.FileSystemException;
	import org.apache.commons.vfs.VfsLog;
	import org.apache.commons.vfs.operations.FileOperationProvider;
	import org.apache.commons.vfs.provider.FileProvider;
	import org.apache.commons.vfs.util.Messages;
	import org.w3c.dom.Element;
	import org.w3c.dom.NodeList;

	/**
	* A {@link org.apache.commons.vfs.FileSystemManager} that configures itself
	* from an XML (Default: providers.xml) configuration file.<br>
	* Certain providers are only loaded and available if the dependend library is in your
	* classpath. You have to configure your debugging facility to log "debug" messages to see
	* if a provider was skipped due to "unresolved externals".
	*
	* @author <a href="mailto:adammurdoch@apache.org">Adam Murdoch</a>
	* @version $Revision$ $Date$
	*/
	public class StandardFileSystemManager
	extends DefaultFileSystemManager
	{
	private static final String CONFIG_RESOURCE = "providers.xml";
	private static final String PLUGIN_CONFIG_RESOURCE = "META-INF/vfs-providers.xml";

	private URL configUri;
	private ClassLoader classLoader;

	/**
	* Sets the configuration file for this manager.
	* @param configUri The URI for this manager.
	*/
	public void setConfiguration(final String configUri)
	{
	try
	{
	setConfiguration(new URL(configUri));
	}
	catch (MalformedURLException e)
	{
	getLogger().warn(e.getLocalizedMessage(), e);
	}
	}

	/**
	* Sets the configuration file for this manager.
	* @param configUri The URI forthis manager.
	*/
	public void setConfiguration(final URL configUri)
	{
	this.configUri = configUri;
	}

	/**
	* Sets the ClassLoader to use to load the providers. Default is to
	* use the ClassLoader that loaded this class.
	* @param classLoader The ClassLoader.
	*/
	public void setClassLoader(final ClassLoader classLoader)
	{
	this.classLoader = classLoader;
	}

	/**
	* Initializes this manager. Adds the providers and replicator.
	* @throws FileSystemException if an error occurs.
	*/
	public void init() throws FileSystemException
	{
	// Set the replicator and temporary file store (use the same component)
	final DefaultFileReplicator replicator = createDefaultFileReplicator();
	setReplicator(new PrivilegedFileReplicator(replicator));
	setTemporaryFileStore(replicator);

	/* replaced by findClassLoader
	if (classLoader == null)
	{
	// Use default classloader
	classLoader = getClass().getClassLoader();
	}
	*/

	if (configUri == null)
	{
	// Use default config
	final URL url = getClass().getResource(CONFIG_RESOURCE);
	if (url == null)
	{
	throw new FileSystemException("vfs.impl/find-config-file.error", CONFIG_RESOURCE);
	}
	configUri = url;
	}

	// Configure
	configure(configUri);

	// Configure Plugins
	configurePlugins();

	// Initialise super-class
	super.init();
	}

	/**
	* Scans the classpath to find any droped plugin.<br />
	* The plugin-description has to be in /META-INF/vfs-providers.xml
	* @throws FileSystemException if an error occurs.
	*/
	protected void configurePlugins() throws FileSystemException
	{
	ClassLoader cl = findClassLoader();

	Enumeration enumResources;
	try
	{
	enumResources = cl.getResources(PLUGIN_CONFIG_RESOURCE);
	}
	catch (IOException e)
	{
	throw new FileSystemException(e);
	}

	while (enumResources.hasMoreElements())
	{
	URL url = (URL) enumResources.nextElement();
	configure(url);
	}
	}

	private ClassLoader findClassLoader()
	{
	if (classLoader != null)
	{
	return classLoader;
	}

	ClassLoader cl = Thread.currentThread().getContextClassLoader();
	if (cl == null)
	{
	cl = getClass().getClassLoader();
	}

	return cl;
	}

	protected DefaultFileReplicator createDefaultFileReplicator()
	{
	return new DefaultFileReplicator();
	}

	/**
	* Configures this manager from an XML configuration file.
	* @param configUri The URI of the configuration.
	* @throws FileSystemException if an error occus.
	*/
	private void configure(final URL configUri) throws FileSystemException
	{
	InputStream configStream = null;
	try
	{
	// Load up the config
	// TODO - validate
	final DocumentBuilder builder = createDocumentBuilder();
	configStream = configUri.openStream();
	final Element config = builder.parse(configStream).getDocumentElement();

	configure(config);
	}
	catch (final Exception e)
	{
	throw new FileSystemException("vfs.impl/load-config.error", configUri.toString(), e);
	}
	finally
	{
	if (configStream != null)
	{
	try
	{
	configStream.close();
	}
	catch (IOException e)
	{
	getLogger().warn(e.getLocalizedMessage(), e);
	}
	}
	}
	}

	/**
	* Configures this manager from an XML configuration file.
	* @param configUri The URI of the configuration.
	* @param configStream An InputStream containing the configuration.
	* @throws FileSystemException if an error occurs.
	*/
	private void configure(final String configUri, final InputStream configStream)
	throws FileSystemException
	{
	try
	{
	// Load up the config
	// TODO - validate
	final DocumentBuilder builder = createDocumentBuilder();
	final Element config = builder.parse(configStream).getDocumentElement();

	configure(config);

	}
	catch (final Exception e)
	{
	throw new FileSystemException("vfs.impl/load-config.error", configUri, e);
	}
	}

	/**
	* Configure and create a DocumentBuilder
	* @return A DocumentBuilder for the configuration.
	* @throws ParserConfigurationException if an error occurs.
	*/
	private DocumentBuilder createDocumentBuilder() throws ParserConfigurationException
	{
	final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
	factory.setIgnoringElementContentWhitespace(true);
	factory.setIgnoringComments(true);
	factory.setExpandEntityReferences(true);
	return factory.newDocumentBuilder();
	}

	/**
	* Configures this manager from an parsed XML configuration file
	* @param config The configuration Element.
	* @throws FileSystemException if an error occurs.
	*/
	private void configure(final Element config) throws FileSystemException
	{
	// Add the providers
	final NodeList providers = config.getElementsByTagName("provider");
	final int count = providers.getLength();
	for (int i = 0; i < count; i++)
	{
	final Element provider = (Element) providers.item(i);
	addProvider(provider, false);
	}

	// Add the operation providers
	final NodeList operationProviders = config.getElementsByTagName("operationProvider");
	for (int i = 0; i < operationProviders.getLength(); i++)
	{
	final Element operationProvider = (Element) operationProviders.item(i);
	addOperationProvider(operationProvider);
	}

	// Add the default provider
	final NodeList defProviders = config.getElementsByTagName("default-provider");
	if (defProviders.getLength() > 0)
	{
	final Element provider = (Element) defProviders.item(0);
	addProvider(provider, true);
	}

	// Add the mime-type maps
	final NodeList mimeTypes = config.getElementsByTagName("mime-type-map");
	for (int i = 0; i < mimeTypes.getLength(); i++)
	{
	final Element map = (Element) mimeTypes.item(i);
	addMimeTypeMap(map);
	}

	// Add the extension maps
	final NodeList extensions = config.getElementsByTagName("extension-map");
	for (int i = 0; i < extensions.getLength(); i++)
	{
	final Element map = (Element) extensions.item(i);
	addExtensionMap(map);
	}
	}

	/**
	* Adds an extension map.
	* @param map containing the Elements.
	*/
	private void addExtensionMap(final Element map)
	{
	final String extension = map.getAttribute("extension");
	final String scheme = map.getAttribute("scheme");
	if (scheme != null && scheme.length() > 0)
	{
	addExtensionMap(extension, scheme);
	}
	}

	/**
	* Adds a mime-type map.
	* @param map containing the Elements.
	*/
	private void addMimeTypeMap(final Element map)
	{
	final String mimeType = map.getAttribute("mime-type");
	final String scheme = map.getAttribute("scheme");
	addMimeTypeMap(mimeType, scheme);
	}

	/**
	* Adds a provider from a provider definition.
	* @param providerDef the provider definition
	* @param isDefault true if the default should be used.
	* @throws FileSystemException if an error occurs.
	*/
	private void addProvider(final Element providerDef, final boolean isDefault)
	throws FileSystemException
	{
	final String classname = providerDef.getAttribute("class-name");

	// Make sure all required schemes are available
	final String[] requiredSchemes = getRequiredSchemes(providerDef);
	for (int i = 0; i < requiredSchemes.length; i++)
	{
	final String requiredScheme = requiredSchemes[i];
	if (!hasProvider(requiredScheme))
	{
	final String msg = Messages.getString("vfs.impl/skipping-provider-scheme.debug",
	new String[]{classname, requiredScheme});
	VfsLog.debug(getLogger(), getLogger(), msg);
	return;
	}
	}

	// Make sure all required classes are in classpath
	final String[] requiredClasses = getRequiredClasses(providerDef);
	for (int i = 0; i < requiredClasses.length; i++)
	{
	final String requiredClass = requiredClasses[i];
	if (!findClass(requiredClass))
	{
	final String msg = Messages.getString("vfs.impl/skipping-provider.debug",
	new String[]{classname, requiredClass});
	VfsLog.debug(getLogger(), getLogger(), msg);
	return;
	}
	}

	// Create and register the provider
	final FileProvider provider = (FileProvider) createInstance(classname);
	final String[] schemas = getSchemas(providerDef);
	if (schemas.length > 0)
	{
	addProvider(schemas, provider);
	}

	// Set as default, if required
	if (isDefault)
	{
	setDefaultProvider(provider);
	}
	}

	/**
	* Adds a operationProvider from a operationProvider definition.
	*/
	private void addOperationProvider(final Element providerDef) throws FileSystemException
	{
	final String classname = providerDef.getAttribute("class-name");

	// Attach only to available schemas
	final String[] schemas = getSchemas(providerDef);
	for (int i = 0; i < schemas.length; i++)
	{
	final String schema = schemas[i];
	if (hasProvider(schema))
	{
	final FileOperationProvider operationProvider = (FileOperationProvider) createInstance(classname);
	addOperationProvider(schema, operationProvider);
	}
	}
	}

	/**
	* Tests if a class is available.
	*/
	private boolean findClass(final String className)
	{
	try
	{
	findClassLoader().loadClass(className);
	return true;
	}
	catch (final ClassNotFoundException e)
	{
	return false;
	}
	}

	/**
	* Extracts the required classes from a provider definition.
	*/
	private String[] getRequiredClasses(final Element providerDef)
	{
	final ArrayList classes = new ArrayList();
	final NodeList deps = providerDef.getElementsByTagName("if-available");
	final int count = deps.getLength();
	for (int i = 0; i < count; i++)
	{
	final Element dep = (Element) deps.item(i);
	String className = dep.getAttribute("class-name");
	if (className != null && className.length() > 0)
	{
	classes.add(className);
	}
	}
	return (String[]) classes.toArray(new String[classes.size()]);
	}

	/**
	* Extracts the required schemes from a provider definition.
	*/
	private String[] getRequiredSchemes(final Element providerDef)
	{
	final ArrayList schemes = new ArrayList();
	final NodeList deps = providerDef.getElementsByTagName("if-available");
	final int count = deps.getLength();
	for (int i = 0; i < count; i++)
	{
	final Element dep = (Element) deps.item(i);
	String scheme = dep.getAttribute("scheme");
	if (scheme != null && scheme.length() > 0)
	{
	schemes.add(scheme);
	}
	}
	return (String[]) schemes.toArray(new String[schemes.size()]);
	}

	/**
	* Extracts the schema names from a provider definition.
	*/
	private String[] getSchemas(final Element provider)
	{
	final ArrayList schemas = new ArrayList();
	final NodeList schemaElements = provider.getElementsByTagName("scheme");
	final int count = schemaElements.getLength();
	for (int i = 0; i < count; i++)
	{
	final Element scheme = (Element) schemaElements.item(i);
	schemas.add(scheme.getAttribute("name"));
	}
	return (String[]) schemas.toArray(new String[schemas.size()]);
	}

	/**
	* Creates a provider.
	*/
	private Object createInstance(final String className)
	throws FileSystemException
	{
	try
	{
	final Class clazz = findClassLoader().loadClass(className);
	return clazz.newInstance();
	}
	catch (final Exception e)
	{
	throw new FileSystemException("vfs.impl/create-provider.error", className, e);
	}
	}
	}