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package sun.net.ftp;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ServiceConfigurationError;
//import java.util.ServiceLoader;

Service provider class for FtpClient. Sub-classes of FtpClientProvider provide an implementation of FtpClient and associated classes. Applications do not normally use this class directly. See provider() for how providers are found and loaded.
Since:1.7
/** * Service provider class for FtpClient. * Sub-classes of FtpClientProvider provide an implementation of {@link FtpClient} * and associated classes. Applications do not normally use this class directly. * See {@link #provider() } for how providers are found and loaded. * * @since 1.7 */
public abstract class FtpClientProvider {
Creates a FtpClient from this provider.
Returns:The created FtpClient.
/** * Creates a FtpClient from this provider. * * @return The created {@link FtpClient}. */
public abstract FtpClient createFtpClient(); private static final Object lock = new Object(); private static FtpClientProvider provider = null;
Initializes a new instance of this class.
Throws:
  • SecurityException – if a security manager is installed and it denies RuntimePermission("ftpClientProvider")
/** * Initializes a new instance of this class. * * @throws SecurityException if a security manager is installed and it denies * {@link RuntimePermission}{@code ("ftpClientProvider")} */
protected FtpClientProvider() { SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("ftpClientProvider")); } } private static boolean loadProviderFromProperty() { String cm = System.getProperty("sun.net.ftpClientProvider"); if (cm == null) { return false; } try { @SuppressWarnings("deprecation") Object o = Class.forName(cm, true, null).newInstance(); provider = (FtpClientProvider)o; return true; } catch (ClassNotFoundException | IllegalAccessException | InstantiationException | SecurityException x) { throw new ServiceConfigurationError(x.toString()); } } private static boolean loadProviderAsService() { // Iterator<FtpClientProvider> i = // ServiceLoader.load(FtpClientProvider.class, // ClassLoader.getSystemClassLoader()).iterator(); // // while (i.hasNext()) { // try { // provider = i.next(); // return true; // } catch (ServiceConfigurationError sce) { // if (sce.getCause() instanceof SecurityException) { // // Ignore, try next provider, if any // continue; // } // throw sce; // } // } return false; }
Returns the system wide default FtpClientProvider for this invocation of the Java virtual machine.

The first invocation of this method locates the default provider object as follows:

  1. If the system property java.net.FtpClientProvider is defined then it is taken to be the fully-qualified name of a concrete provider class. The class is loaded and instantiated; if this process fails then an unspecified unchecked error or exception is thrown.

  2. If a provider class has been installed in a jar file that is visible to the system class loader, and that jar file contains a provider-configuration file named java.net.FtpClientProvider in the resource directory META-INF/services, then the first class name specified in that file is taken. The class is loaded and instantiated; if this process fails then an unspecified unchecked error or exception is thrown.

  3. Finally, if no provider has been specified by any of the above means then the system-default provider class is instantiated and the result is returned.

Subsequent invocations of this method return the provider that was returned by the first invocation.

Returns: The system-wide default FtpClientProvider
/** * Returns the system wide default FtpClientProvider for this invocation of * the Java virtual machine. * * <p> The first invocation of this method locates the default provider * object as follows: </p> * * <ol> * * <li><p> If the system property * {@code java.net.FtpClientProvider} is defined then it is * taken to be the fully-qualified name of a concrete provider class. * The class is loaded and instantiated; if this process fails then an * unspecified unchecked error or exception is thrown. </p></li> * * <li><p> If a provider class has been installed in a jar file that is * visible to the system class loader, and that jar file contains a * provider-configuration file named * {@code java.net.FtpClientProvider} in the resource * directory {@code META-INF/services}, then the first class name * specified in that file is taken. The class is loaded and * instantiated; if this process fails then an unspecified unchecked error or exception is * thrown. </p></li> * * <li><p> Finally, if no provider has been specified by any of the above * means then the system-default provider class is instantiated and the * result is returned. </p></li> * * </ol> * * <p> Subsequent invocations of this method return the provider that was * returned by the first invocation. </p> * * @return The system-wide default FtpClientProvider */
public static FtpClientProvider provider() { synchronized (lock) { if (provider != null) { return provider; } return (FtpClientProvider) AccessController.doPrivileged( new PrivilegedAction<Object>() { public Object run() { if (loadProviderFromProperty()) { return provider; } if (loadProviderAsService()) { return provider; } provider = new sun.net.ftp.impl.DefaultFtpClientProvider(); return provider; } }); } } }