* returns the Provider that appeared first in the      * configuration files. If an implementation for the protocol      * isn't found, throws NoSuchProviderException     *     * @param  protocol  Configured protocol (i.e. smtp, imap, etc)     * @return Currently configured Provider for the specified protocol     * @exception	NoSuchProviderException If a provider for the given     *			protocol is not found.     */    public synchronized Provider getProvider(String protocol)	                                throws NoSuchProviderException {	if (protocol == null || protocol.length() <= 0) {	    throw new NoSuchProviderException("Invalid protocol: null");	}	Provider _provider = null;	// check if the mail.<protocol>.class property exists	String _className = props.getProperty("mail."+protocol+".class");	if (_className != null) {	    if (debug) {		pr("DEBUG: mail."+protocol+				   ".class property exists and points to " + 				   _className);	    }	    _provider = (Provider)providersByClassName.get(_className);	} 	if (_provider != null) {	    return _provider;	} else {	    // returning currently default protocol in providersByProtocol	    _provider = (Provider)providersByProtocol.get(protocol);	}	if (_provider == null) {	    throw new NoSuchProviderException("No provider for " + protocol);	} else {	    if (debug) {		pr("DEBUG: getProvider() returning " + 				   _provider.toString());	    }	    return _provider;	}    }    /**     * Set the passed Provider to be the default implementation     * for the protocol in Provider.protocol overriding any previous values.     *     * @param provider Currently configured Provider which will be      * set as the default for the protocol     * @exception	NoSuchProviderException If the provider passed in     *			is invalid.     */    public synchronized void setProvider(Provider provider)				throws NoSuchProviderException {	if (provider == null) {	    throw new NoSuchProviderException("Can't set null provider");	}	providersByProtocol.put(provider.getProtocol(), provider);	props.put("mail." + provider.getProtocol() + ".class", 		  provider.getClassName());    }    /**     * Get a Store object that implements this user's desired Store     * protocol. The <code>mail.store.protocol</code> property specifies the     * desired protocol. If an appropriate Store object is not obtained,      * NoSuchProviderException is thrown     *     * @return 		a Store object      * @exception	NoSuchProviderException If a provider for the given     *			protocol is not found.     */    public Store getStore() throws NoSuchProviderException {	return getStore(getProperty("mail.store.protocol"));    }    /**     * Get a Store object that implements the specified protocol. If an     * appropriate Store object cannot be obtained,      * NoSuchProviderException is thrown.     *     * @param	        protocol     * @return		a Store object      * @exception	NoSuchProviderException If a provider for the given     *			protocol is not found.     */    public Store getStore(String protocol) throws NoSuchProviderException {	return getStore(new URLName(protocol, null, -1, null, null, null));    }    /**     * Get a Store object for the given URLName. If the requested Store     * object cannot be obtained, NoSuchProviderException is thrown.     *     * The "scheme" part of the URL string (Refer RFC 1738) is used      * to locate the Store protocol. <p>     *     * @param	url	URLName that represents the desired Store     * @return		a closed Store object     * @see		#getFolder(URLName)     * @see		javax.mail.URLName     * @exception	NoSuchProviderException If a provider for the given     *			URLName is not found.     */    public Store getStore(URLName url) throws NoSuchProviderException {	String protocol = url.getProtocol();	Provider p = getProvider(protocol);	return getStore(p, url);    }    /**     * Get an instance of the store specified by Provider. Instantiates     * the store and returns it.     *      * @param provider Store Provider that will be instantiated     * @return Instantiated Store     * @exception	NoSuchProviderException If a provider for the given     *			Provider is not found.     */    public Store getStore(Provider provider) throws NoSuchProviderException {	return getStore(provider, null);    }    /**     * Get an instance of the store specified by Provider. If the URLName     * is not null, uses it, otherwise creates a new one. Instantiates     * the store and returns it. This is a private method used by     * getStore(Provider) and getStore(URLName)     *      * @param provider Store Provider that will be instantiated     * @param url      URLName used to instantiate the Store     * @return Instantiated Store     * @exception	NoSuchProviderException If a provider for the given     *			Provider/URLName is not found.     */    private Store getStore(Provider provider, URLName url) 	throws NoSuchProviderException {	// make sure we have the correct type of provider	if (provider == null || provider.getType() != Provider.Type.STORE ) {	    throw new NoSuchProviderException("invalid provider");	}			try {	    return (Store) getService(provider, url);	} catch (ClassCastException cce) {	    throw new NoSuchProviderException("incorrect class");	}    }    /**     * Get a closed Folder object for the given URLName. If the requested     * Folder object cannot be obtained, null is returned. <p>     *     * The "scheme" part of the URL string (Refer RFC 1738) is used     * to locate the Store protocol. The rest of the URL string (that is,     * the "schemepart", as per RFC 1738) is used by that Store     * in a protocol dependent manner to locate and instantiate the     * appropriate Folder object. <p>     *     * Note that RFC 1738 also specifies the syntax for the      * "schemepart" for IP-based protocols (IMAP4, POP3, etc.).     * Providers of IP-based mail Stores should implement that     * syntax for referring to Folders. <p>     *     * @param	url	URLName that represents the desired folder     * @return		Folder     * @see		#getStore(URLName)     * @see		javax.mail.URLName     * @exception	NoSuchProviderException If a provider for the given     *			URLName is not found.     * @exception	MessagingException if the Folder could not be      *			located or created.     */    public Folder getFolder(URLName url)		throws MessagingException {	// First get the Store	Store store = getStore(url);	store.connect();	return store.getFolder(url);    }    /**     * Get a Transport object that implements this user's desired      * Transport protcol. The <code>mail.transport.protocol</code> property      * specifies the desired protocol. If an appropriate Transport      * object cannot be obtained, MessagingException is thrown.     *     * @return 		a Transport object      * @exception	NoSuchProviderException If the provider is not found.     */    public Transport getTransport() throws NoSuchProviderException {        return getTransport(getProperty("mail.transport.protocol"));    }    /**     * Get a Transport object that implements the specified protocol.     * If an appropriate Transport object cannot be obtained, null is     * returned.     *     * @return 		a Transport object      * @exception	NoSuchProviderException If provider for the given     *			protocol is not found.     */    public Transport getTransport(String protocol)				throws NoSuchProviderException {	return getTransport(new URLName(protocol, null, -1, null, null, null));    }    /**     * Get a Transport object for the given URLName. If the requested      * Transport object cannot be obtained, NoSuchProviderException is thrown.     *     * The "scheme" part of the URL string (Refer RFC 1738) is used      * to locate the Transport protocol. <p>     *     * @param	url	URLName that represents the desired Transport     * @return		a closed Transport object     * @see		javax.mail.URLName     * @exception	NoSuchProviderException If a provider for the given     *			URLName is not found.     */    public Transport getTransport(URLName url) throws NoSuchProviderException {	String protocol = url.getProtocol();	Provider p = getProvider(protocol);	return getTransport(p, url);    }    /**     * Get an instance of the transport specified in the Provider. Instantiates     * the transport and returns it.     *      * @param provider Transport Provider that will be instantiated     * @return Instantiated Transport     * @exception	NoSuchProviderException If provider for the given     *			provider is not found.     */    public Transport getTransport(Provider provider) 	                                     throws NoSuchProviderException {	return getTransport(provider, null);    }    /**     * Get a Transport object that can transport a Message to the     * specified address type.     *     * @param	address     * @return	A Transport object     * @see javax.mail.Address     * @exception	NoSuchProviderException If provider for the      *			Address type is not found     */    public Transport getTransport(Address address) 	                                     throws NoSuchProviderException {	String transportProtocol = (String)addressMap.get(address.getType());	if (transportProtocol == null) {	    throw new NoSuchProviderException("No provider for Address type: "+					      address.getType());	} else {	    return getTransport(transportProtocol);	}    }    /**     * Get a Transport object using the given provider and urlname.     *     * @param	provider	the provider to use     * @param	url		urlname to use (can be null)     * @return A Transport object     * @exception	NoSuchProviderException	If no provider or the provider     *			was the wrong class.	     */    private Transport getTransport(Provider provider, URLName url)					throws NoSuchProviderException {	// make sure we have the correct type of provider	if (provider == null || provider.getType() != Provider.Type.TRANSPORT) {	    throw new NoSuchProviderException("invalid provider");	}	try {	    return (Transport) getService(provider, url);	} catch (ClassCastException cce) {	    throw new NoSuchProviderException("incorrect class");	}    }    /**     * Get a Service object.  Needs a provider object, but will     * create a URLName if needed.  It attempts to instantiate     * the correct class.     *     * @param provider	which provider to use     * @param url	which URLName to use (can be null)     * @exception	NoSuchProviderException	thrown when the class cannot be     *			found or when it does not have the correct constructor     *			(Session, URLName), or if it is not derived from     *			Service.     */    private Object getService(Provider provider, URLName url)					throws NoSuchProviderException {	// need a provider and url	if (provider == null) {	    throw new NoSuchProviderException("null");	}	// create a url if needed	if (url == null) {	    url = new URLName(provider.getProtocol(), null, -1, 			      null, null, null);	}	Object service = null;		// get the ClassLoader associated with the Authenticator	ClassLoader cl;	if (authenticator != null)	    cl = authenticator.getClass().getClassLoader();	else	    cl = this.getClass().getClassLoader();	// now load the class	Class serviceClass = null;	try {	    // First try the "application's" class loader.	    ClassLoader ccl = getContextClassLoader();	    if (ccl != null)		try {		    serviceClass = ccl.loadClass(provider.getClassName());		} catch (ClassNotFoundException ex) {		    // ignore it		}	    if (serviceClass == null)		serviceClass = cl.loadClass(provider.getClassName());	} catch (Exception ex1) {	    // That didn't work, now try the "system" class loader.	    // (Need both of these because JDK 1.1 class loaders	    // may not delegate to their parent class loader.)	    try {		serviceClass = Class.forName(provider.getClassName());	    } catch (Exception ex) {		// Nothing worked, give up.		if (debug) ex.printStackTrace(getDebugOut());		throw new NoSuchProviderException(provider.getProtocol());	    }	}	// construct an instance of the class	try {	    Class[] c = {javax.mail.Session.class, javax.mail.URLName.class};	    Constructor cons = serviceClass.getConstructor(c);	    Object[] o = {this, url};	    service = cons.newInstance(o);	} catch (Exception ex) {	    if (debug) ex.printStackTrace(getDebugOut());	    throw new NoSuchProviderException(provider.getProtocol());	}	return service;    }    /**     * Save a PasswordAuthentication for this (store or transport) URLName.     * If pw is null the entry corresponding to the URLName is removed.     * <p>     * This is normally used only by the store or transport implementations     * to allow authentication information to be shared among multiple     * uses of a session.     */    public void setPasswordAuthentication(URLName url,					  PasswordAuthentication pw) {	if (pw == null)	    authTable.remove(url);	else	    authTable.put(url, pw);    }    /**     * Return any saved PasswordAuthentication for this (store or transport)     * URLName.  Normally used only by store or transport implementations.     *     * @return	the PasswordAuthentication corresponding to the URLName     */    public PasswordAuthentication getPasswordAuthentication(URLName url) {	return (PasswordAuthentication)authTable.get(url);    }    /**     * Call back to the application to get the needed user name and password.     * The application should put up a dialog something like:     * <p> <pre>     * Connecting to &lt;protocol&gt; mail service on host &lt;addr&gt;, port &lt;port&gt;.     * &lt;prompt&gt;     *     * User Name: &lt;defaultUserName&gt;     * Password:     * </pre>     *     * @param	addr		InetAddress of the host.  may be null.     * @param	protocol	protocol scheme (e.g. imap, pop3, etc.)     * @param	prompt		any additional String to show as part of     *                          the prompt; may be null.     * @param	defaultUserName	the default username. may be null.     * @return	the authentication which was collected by the authenticator;      *          may be null.     */    public PasswordAuthentication requestPasswordAuthentication(	InetAddress addr, int port,	String protocol, String prompt, String defaultUserName) {	if (authenticator != null) {	    return authenticator.requestPasswordAuthentication(		addr, port, protocol, prompt, defaultUserName);	} else {	    return null;	}