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package java.nio.channels.spi;

import java.nio.channels.*;
import java.io.IOException;
import java.util.Iterator;
import java.util.ServiceLoader;
import java.util.ServiceConfigurationError;
import java.util.concurrent.*;
import java.security.AccessController;
import java.security.PrivilegedAction;

Service-provider class for asynchronous channels.

An asynchronous channel provider is a concrete subclass of this class that has a zero-argument constructor and implements the abstract methods specified below. A given invocation of the Java virtual machine maintains a single system-wide default provider instance, which is returned by the provider method. The first invocation of that method will locate the default provider as specified below.

All of the methods in this class are safe for use by multiple concurrent threads.

Since:1.7
/** * Service-provider class for asynchronous channels. * * <p> An asynchronous channel provider is a concrete subclass of this class that * has a zero-argument constructor and implements the abstract methods specified * below. A given invocation of the Java virtual machine maintains a single * system-wide default provider instance, which is returned by the {@link * #provider() provider} method. The first invocation of that method will locate * the default provider as specified below. * * <p> All of the methods in this class are safe for use by multiple concurrent * threads. </p> * * @since 1.7 */
public abstract class AsynchronousChannelProvider { private static Void checkPermission() { SecurityManager sm = System.getSecurityManager(); if (sm != null) sm.checkPermission(new RuntimePermission("asynchronousChannelProvider")); return null; } private AsynchronousChannelProvider(Void ignore) { }
Initializes a new instance of this class.
Throws:
  • SecurityException – If a security manager has been installed and it denies RuntimePermission("asynchronousChannelProvider")
/** * Initializes a new instance of this class. * * @throws SecurityException * If a security manager has been installed and it denies * {@link RuntimePermission}{@code ("asynchronousChannelProvider")} */
protected AsynchronousChannelProvider() { this(checkPermission()); } // lazy initialization of default provider private static class ProviderHolder { static final AsynchronousChannelProvider provider = load(); private static AsynchronousChannelProvider load() { return AccessController .doPrivileged(new PrivilegedAction<>() { public AsynchronousChannelProvider run() { AsynchronousChannelProvider p; p = loadProviderFromProperty(); if (p != null) return p; p = loadProviderAsService(); if (p != null) return p; return sun.nio.ch.DefaultAsynchronousChannelProvider.create(); }}); } private static AsynchronousChannelProvider loadProviderFromProperty() { String cn = System.getProperty("java.nio.channels.spi.AsynchronousChannelProvider"); if (cn == null) return null; try { @SuppressWarnings("deprecation") Object tmp = Class.forName(cn, true, ClassLoader.getSystemClassLoader()).newInstance(); return (AsynchronousChannelProvider)tmp; } catch (ClassNotFoundException x) { throw new ServiceConfigurationError(null, x); } catch (IllegalAccessException x) { throw new ServiceConfigurationError(null, x); } catch (InstantiationException x) { throw new ServiceConfigurationError(null, x); } catch (SecurityException x) { throw new ServiceConfigurationError(null, x); } } private static AsynchronousChannelProvider loadProviderAsService() { ServiceLoader<AsynchronousChannelProvider> sl = ServiceLoader.load(AsynchronousChannelProvider.class, ClassLoader.getSystemClassLoader()); Iterator<AsynchronousChannelProvider> i = sl.iterator(); for (;;) { try { return (i.hasNext()) ? i.next() : null; } catch (ServiceConfigurationError sce) { if (sce.getCause() instanceof SecurityException) { // Ignore the security exception, try the next provider continue; } throw sce; } } } }
Returns the system-wide default asynchronous channel provider 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.nio.channels.spi.AsynchronousChannelProvider 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 error 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.nio.channels.spi.AsynchronousChannelProvider 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 error 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 AsynchronousChannel provider
/** * Returns the system-wide default asynchronous channel provider 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 * {@systemProperty java.nio.channels.spi.AsynchronousChannelProvider} 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 error 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.nio.channels.spi.AsynchronousChannelProvider} 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 error 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 AsynchronousChannel provider */
public static AsynchronousChannelProvider provider() { return ProviderHolder.provider; }
Constructs a new asynchronous channel group with a fixed thread pool.
Params:
  • nThreads – The number of threads in the pool
  • threadFactory – The factory to use when creating new threads
Throws:
See Also:
Returns: A new asynchronous channel group
/** * Constructs a new asynchronous channel group with a fixed thread pool. * * @param nThreads * The number of threads in the pool * @param threadFactory * The factory to use when creating new threads * * @return A new asynchronous channel group * * @throws IllegalArgumentException * If {@code nThreads <= 0} * @throws IOException * If an I/O error occurs * * @see AsynchronousChannelGroup#withFixedThreadPool */
public abstract AsynchronousChannelGroup openAsynchronousChannelGroup(int nThreads, ThreadFactory threadFactory) throws IOException;
Constructs a new asynchronous channel group with the given thread pool.
Params:
  • executor – The thread pool
  • initialSize – A value >=0 or a negative value for implementation specific default
Throws:
See Also:
Returns: A new asynchronous channel group
/** * Constructs a new asynchronous channel group with the given thread pool. * * @param executor * The thread pool * @param initialSize * A value {@code >=0} or a negative value for implementation * specific default * * @return A new asynchronous channel group * * @throws IOException * If an I/O error occurs * * @see AsynchronousChannelGroup#withCachedThreadPool */
public abstract AsynchronousChannelGroup openAsynchronousChannelGroup(ExecutorService executor, int initialSize) throws IOException;
Opens an asynchronous server-socket channel.
Params:
  • group – The group to which the channel is bound, or null to bind to the default group
Throws:
Returns: The new channel
/** * Opens an asynchronous server-socket channel. * * @param group * The group to which the channel is bound, or {@code null} to * bind to the default group * * @return The new channel * * @throws IllegalChannelGroupException * If the provider that created the group differs from this provider * @throws ShutdownChannelGroupException * The group is shutdown * @throws IOException * If an I/O error occurs */
public abstract AsynchronousServerSocketChannel openAsynchronousServerSocketChannel (AsynchronousChannelGroup group) throws IOException;
Opens an asynchronous socket channel.
Params:
  • group – The group to which the channel is bound, or null to bind to the default group
Throws:
Returns: The new channel
/** * Opens an asynchronous socket channel. * * @param group * The group to which the channel is bound, or {@code null} to * bind to the default group * * @return The new channel * * @throws IllegalChannelGroupException * If the provider that created the group differs from this provider * @throws ShutdownChannelGroupException * The group is shutdown * @throws IOException * If an I/O error occurs */
public abstract AsynchronousSocketChannel openAsynchronousSocketChannel (AsynchronousChannelGroup group) throws IOException; }