java.nio.channels.spi.SelectorProvider Maven / Gradle / Ivy
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
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*
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package java.nio.channels.spi;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.ProtocolFamily;
import java.nio.channels.Channel;
import java.nio.channels.DatagramChannel;
import java.nio.channels.Pipe;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Iterator;
import java.util.Objects;
import java.util.ServiceLoader;
import java.util.ServiceConfigurationError;
/**
* Service-provider class for selectors and selectable channels.
*
* A selector 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.
*
*
The system-wide default provider is used by the static {@code open}
* methods of the {@link java.nio.channels.DatagramChannel#open
* DatagramChannel}, {@link java.nio.channels.Pipe#open Pipe}, {@link
* java.nio.channels.Selector#open Selector}, {@link
* java.nio.channels.ServerSocketChannel#open ServerSocketChannel}, and {@link
* java.nio.channels.SocketChannel#open SocketChannel} classes. It is also
* used by the {@link java.lang.System#inheritedChannel System.inheritedChannel()}
* method. A program may make use of a provider other than the default provider
* by instantiating that provider and then directly invoking the {@code open}
* methods defined in this class.
*
*
All of the methods in this class are safe for use by multiple concurrent
* threads.
*
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
*/
public abstract class SelectorProvider {
private static Void checkPermission() {
@SuppressWarnings("removal")
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(new RuntimePermission("selectorProvider"));
return null;
}
private SelectorProvider(Void ignore) { }
/**
* Initializes a new instance of this class.
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link RuntimePermission}{@code ("selectorProvider")}
*/
protected SelectorProvider() {
this(checkPermission());
}
private static class Holder {
static final SelectorProvider INSTANCE = provider();
@SuppressWarnings("removal")
static SelectorProvider provider() {
PrivilegedAction pa = () -> {
SelectorProvider sp;
if ((sp = loadProviderFromProperty()) != null)
return sp;
if ((sp = loadProviderAsService()) != null)
return sp;
return sun.nio.ch.DefaultSelectorProvider.get();
};
return AccessController.doPrivileged(pa);
}
private static SelectorProvider loadProviderFromProperty() {
String cn = System.getProperty("java.nio.channels.spi.SelectorProvider");
if (cn == null)
return null;
try {
Class clazz = Class.forName(cn, true, ClassLoader.getSystemClassLoader());
return (SelectorProvider) clazz.getConstructor().newInstance();
} catch (ClassNotFoundException |
NoSuchMethodException |
IllegalAccessException |
InvocationTargetException |
InstantiationException |
SecurityException x) {
throw new ServiceConfigurationError(null, x);
}
}
private static SelectorProvider loadProviderAsService() {
ServiceLoader sl =
ServiceLoader.load(SelectorProvider.class,
ClassLoader.getSystemClassLoader());
Iterator 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 selector provider for this invocation of
* the Java virtual machine.
*
* The first invocation of this method locates the default provider
* object as follows:
*
*
*
* If the system property
* {@systemProperty java.nio.channels.spi.SelectorProvider} 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.
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.SelectorProvider} 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.
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.
*
* @return The system-wide default selector provider
*/
public static SelectorProvider provider() {
return Holder.INSTANCE;
}
/**
* Opens a datagram channel.
*
* @return The new channel
*
* @throws IOException
* If an I/O error occurs
*/
public abstract DatagramChannel openDatagramChannel()
throws IOException;
/**
* Opens a datagram channel.
*
* @param family
* The protocol family
*
* @return A new datagram channel
*
* @throws UnsupportedOperationException
* If the specified protocol family is not supported
* @throws IOException
* If an I/O error occurs
*
* @since 1.7
*/
public abstract DatagramChannel openDatagramChannel(ProtocolFamily family)
throws IOException;
/**
* Opens a pipe.
*
* @return The new pipe
*
* @throws IOException
* If an I/O error occurs
*/
public abstract Pipe openPipe()
throws IOException;
/**
* Opens a selector.
*
* @return The new selector
*
* @throws IOException
* If an I/O error occurs
*/
public abstract AbstractSelector openSelector()
throws IOException;
/**
* Opens a server-socket channel.
*
* @return The new channel
*
* @throws IOException
* If an I/O error occurs
*/
public abstract ServerSocketChannel openServerSocketChannel()
throws IOException;
/**
* Opens a socket channel.
*
* @return The new channel
*
* @throws IOException
* If an I/O error occurs
*/
public abstract SocketChannel openSocketChannel()
throws IOException;
/**
* Returns the channel inherited from the entity that created this
* Java virtual machine.
*
* On many operating systems a process, such as a Java virtual
* machine, can be started in a manner that allows the process to
* inherit a channel from the entity that created the process. The
* manner in which this is done is system dependent, as are the
* possible entities to which the channel may be connected. For example,
* on UNIX systems, the Internet services daemon (inetd) is used to
* start programs to service requests when a request arrives on an
* associated network port. In this example, the process that is started,
* inherits a channel representing a network socket.
*
*
In cases where the inherited channel is for an Internet protocol
* socket then the {@link Channel Channel} type returned
* by this method is determined as follows:
*
*
*
* If the inherited channel is for a stream-oriented connected
* socket then a {@link SocketChannel SocketChannel} is returned. The
* socket channel is, at least initially, in blocking mode, bound
* to a socket address, and connected to a peer.
*
If the inherited channel is for a stream-oriented listening
* socket then a {@link ServerSocketChannel ServerSocketChannel} is returned.
* The server-socket channel is, at least initially, in blocking mode,
* and bound to a socket address.
*
If the inherited channel is a datagram-oriented socket then a
* {@link DatagramChannel DatagramChannel} is returned. The datagram channel
* is, at least initially, in blocking mode, and bound to a socket address.
*
*
* In cases where the inherited channel is for a Unix domain
* socket then the {@link Channel} type returned is the same as for
* Internet protocol sockets as described above, except that
* datagram-oriented sockets are not supported.
*
*
In addition to the two types of socket just described, this method
* may return other types in the future.
*
*
The first invocation of this method creates the channel that is
* returned. Subsequent invocations of this method return the same
* channel.
*
* @implSpec The default implementation of this method returns
* {@code null}.
*
* @return The inherited channel, if any, otherwise {@code null}.
*
* @throws IOException
* If an I/O error occurs
*
* @throws SecurityException
* If a security manager has been installed and it denies
* {@link RuntimePermission}{@code ("inheritedChannel")}
*
* @since 1.5
*/
public Channel inheritedChannel() throws IOException {
return null;
}
/**
* Opens a socket channel.
*
* @implSpec The default implementation of this method first checks that
* the given protocol {@code family} is not {@code null},
* then throws {@link UnsupportedOperationException}.
*
* @param family
* The protocol family
*
* @return The new channel
*
* @throws UnsupportedOperationException
* If the specified protocol family is not supported
* @throws IOException
* If an I/O error occurs
*
* @since 15
*/
public SocketChannel openSocketChannel(ProtocolFamily family) throws IOException {
Objects.requireNonNull(family);
throw new UnsupportedOperationException("Protocol family not supported");
}
/**
* Opens a server-socket channel.
*
* @implSpec The default implementation of this method first checks that
* the given protocol {@code family} is not {@code null},
* then throws {@link UnsupportedOperationException}.
*
* @param family
* The protocol family
*
* @return The new channel
*
* @throws UnsupportedOperationException
* If the specified protocol family is not supported
* @throws IOException
* If an I/O error occurs
*
* @since 15
*/
public ServerSocketChannel openServerSocketChannel(ProtocolFamily family) throws IOException {
Objects.requireNonNull(family);
throw new UnsupportedOperationException("Protocol family not supported");
}
}