NetworkChannel接口定义

Channel接口定义：http://donald-draper.iteye.com/blog/2369111
AbstractInterruptibleChannel接口定义：http://donald-draper.iteye.com/blog/2369238
SelectableChannel接口定义:http://donald-draper.iteye.com/blog/2369317
SelectionKey定义：http://donald-draper.iteye.com/blog/2369499
SelectorProvider定义：http://donald-draper.iteye.com/blog/2369615
AbstractSelectableChannel定义：http://donald-draper.iteye.com/blog/2369742
先来回顾一下ServerSocketChannel继承结构树：

//ServerSocketChannel
public abstract class ServerSocketChannel
    extends AbstractSelectableChannel
    implements NetworkChannel

//AbstractSelectableChannel
public abstract class AbstractSelectableChannel
    extends SelectableChannel

//SelectableChannel
public abstract class SelectableChannel
    extends AbstractInterruptibleChannel
    implements Channel

到目前这篇文章之前我们，看完了socket的通道的一个可选择通道分支，在这个过程成，我们
看了一下选择key，通道选择器提供者的定义，今天我们来看另一个分支网络通道：

package java.nio.channels;

import java.net.SocketOption;
import java.net.SocketAddress;
import java.util.Set;
import java.io.IOException;

/**
 * A channel to a network socket.
 *
 * <p> A channel that implements this interface is a channel to a network
 * socket. The {@link #bind(SocketAddress) bind} method is used to bind the
 * socket to a local {@link SocketAddress address}, the {@link #getLocalAddress()
 * getLocalAddress} method returns the address that the socket is bound to, and
 * the {@link #setOption(SocketOption,Object) setOption} and {@link
 * #getOption(SocketOption) getOption} methods are used to set and query socket
 * options.  An implementation of this interface should specify the socket options
 * that it supports.
 *NetworkChannel是一个通道到网络socket的实现，#bind用于绑定一个本地socket地址，
 #getLocalAddress可以返回绑定的地址，#setOption和#getOption用于设置和获取网络通道
 的选项配置。接口的实现应该精确支持的选项配置集。
 * <p> The {@link #bind bind} and {@link #setOption setOption} methods that do
 * not otherwise have a value to return are specified to return the network
 * channel upon which they are invoked. This allows method invocations to be
 * chained. Implementations of this interface should specialize the return type
 * so that method invocations on the implementation class can be chained.
 * #bind和#setOption在调用时，不一定非要返回网络通道，允许被链式调用。网络通道的
 具体实现应该明确#bind和#setOption的返回类型，以便可以链式调用。
 * @since 1.7
 */

public interface NetworkChannel
    extends Channel
{
    /**
     * Binds the channel's socket to a local address.
     *绑定通道socket到本地地址
     * <p> This method is used to establish an association between the socket and
     * a local address. Once an association is established then the socket remains
     * bound until the channel is closed. If the {@code local} parameter has the
     * value {@code null} then the socket will be bound to an address that is
     * assigned automatically.
     *bind的方法用于建立socket和本地地址的关系。只要关系建立，在通道没关闭之前socket
     仍绑定着本地SocketAddress。如果socket地址参数为null，默认socket将绑定自动分配的地址
     * @param   local
     *          The address to bind the socket, or {@code null} to bind the socket
     *          to an automatically assigned socket address
     *
     * @return  This channel
     *
     * @throws  AlreadyBoundException 已绑定
     *          If the socket is already bound
     * @throws  UnsupportedAddressTypeException 不支持地址类型
     *          If the type of the given address is not supported
     * @throws  ClosedChannelException 通道关闭
     *          If the channel is closed
     * @throws  IOException 操作异常
     *          If some other I/O error occurs
     * @throws  SecurityException 权限访问异常
     *          If a security manager is installed and it denies an unspecified
     *          permission. An implementation of this interface should specify
     *          any required permissions.
     *
     * @see #getLocalAddress
     */
    NetworkChannel bind(SocketAddress local) throws IOException;

    /**
     * Returns the socket address that this channel's socket is bound to, or
     * {@code null} if the socket is not bound.
     *返回socket通道绑定的socket地址，如果为null，即没有绑定。
     * <p> Where the channel is {@link #bind bound} to an Internet Protocol
     * socket address then the return value from this method is of type {@link
     * java.net.InetSocketAddress}.
     *如果通道绑定到一个网络协议socket地址，将会返回一个InetSocketAddress的地址
     * @return  The socket address that the socket is bound to, or {@code null}
     *          if the channel's socket is not bound
     *
     * @throws  ClosedChannelException 通道已关闭
     *          If the channel is closed
     * @throws  IOException IO操作异常
     *          If an I/O error occurs
     */
    SocketAddress getLocalAddress() throws IOException;

    /**
     * Sets the value of a socket option.
     * 设置socket选项值
     * @param   name
     *          The socket option
     * @param   value，值为null，对某些socket选项也许是一个有效的值
     *          The value of the socket option. A value of {@code null} may be
     *          a valid value for some socket options.
     *
     * @return  This channel
     *
     * @throws  UnsupportedOperationException ，如果socket选项不被通道支持
     *          If the socket option is not supported by this channel
     * @throws  IllegalArgumentException  如果值对socket选项是一个无效的值
     *          If the value is not a valid value for this socket option
     * @throws  ClosedChannelException 通道关闭
     *          If this channel is closed
     * @throws  IOException 通道IO异常
     *          If an I/O error occurs
     *
     * @see java.net.StandardSocketOptions
     */
    <T> NetworkChannel setOption(SocketOption<T> name, T value) throws IOException;

    /**
     * Returns the value of a socket option.
     * 获取socket选项的值
     * @param   name
     *          The socket option
     *
     * @return  The value of the socket option. A value of {@code null} may be
     *          a valid value for some socket options.
     *
     * @throws  UnsupportedOperationException
     *          If the socket option is not supported by this channel
     * @throws  ClosedChannelException
     *          If this channel is closed
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @see java.net.StandardSocketOptions
     */
    <T> T getOption(SocketOption<T> name) throws IOException;

    /**
     * Returns a set of the socket options supported by this channel.
     *返回通道支持的socket选项
     * <p> This method will continue to return the set of options even after the
     * channel has been closed.
     *即使在通道关闭时，此方法仍返回socket配置选项集
     * @return  A set of the socket options supported by this channel
     */
    Set<SocketOption<?>> supportedOptions();
}

从网络通道NetworkChannel的定义来看，主要作用是绑定socket的local地址，获取绑定的地址，
以及设置或获取socket选项。

//SocketOption

package java.net;
/**
 * A socket option associated with a socket.
 * SocketOption为与socket关联的选项配置
 * <p> In the {@link java.nio.channels channels} package, the {@link
 * java.nio.channels.NetworkChannel} interface defines the {@link
 * java.nio.channels.NetworkChannel#setOption(SocketOption,Object) setOption}
 * and {@link java.nio.channels.NetworkChannel#getOption(SocketOption) getOption}
 * methods to set and query the channel's socket options.
 *在网络通道NetworkChannel中定义了设置和获取socket选择配置的方法。
 * @param   <T>     The type of the socket option value.
 *
 * @since 1.7
 *
 * @see StandardSocketOptions
 */

public interface SocketOption<T> {

    /**
     * Returns the name of the socket option.
     选型名称
     */
    String name();

    /**
     * Returns the type of the socket option value.
     选项类型
     */
    Class<T> type();
}