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netty学习之Channel接口

发表于: 2013-01-11   作者:asialee   来源:转载   浏览次数:
摘要:     正如javadoc所说的,一个channel给用户提供下面四个服务:1. 当前channel的状态,是open还是connected2. 这个channel的一些配置信息3. 这个channel所支持的一些io操作4. 和这个channel相关联的ChannelPipelineChannel中所有的操作都是异步的,当发生io操作的时候将会返回一个 ChannelFutr

    正如javadoc所说的,一个channel给用户提供下面四个服务:
1. 当前channel的状态,是open还是connected
2. 这个channel的一些配置信息
3. 这个channel所支持的一些io操作
4. 和这个channel相关联的ChannelPipeline
Channel中所有的操作都是异步的,当发生io操作的时候将会返回一个
ChannelFutrue的接口,在这个里面可以处理操作成功、失败、取消后的动作。
在netty里面,随着Channel的创建者的不同可以分成不同的一些channel,比如它可以被ServerSocketChannel的accept之后,返回一个SocketChannel,这个SocketChannel的parent就是ServerSocketChannel了,在netty里面应该有三类Channel,这个会在以后详细讲解。
Channel里面的interestOps的和NIO里面的SelectionKey有点类似,这个会在以后进行详细的说明。

 

public interface Channel extends Comparable<Channel> {

    /**
     * The {@link #getInterestOps() interestOps} value which tells that only
     * read operation has been suspended.
     */
    static int OP_NONE = 0;

    /**
     * The {@link #getInterestOps() interestOps} value which tells that neither
     * read nor write operation has been suspended.
     */
    static int OP_READ = 1;

    /**
     * The {@link #getInterestOps() interestOps} value which tells that both
     * read and write operation has been suspended.
     */
    static int OP_WRITE = 4;

    /**
     * The {@link #getInterestOps() interestOps} value which tells that only
     * write operation has been suspended.
     */
    static int OP_READ_WRITE = OP_READ | OP_WRITE;

    /**
     * Returns the unique integer ID of this channel.
     */
    Integer getId();

    /**
     * Returns the {@link ChannelFactory} which created this channel.
     */
    ChannelFactory getFactory();

    /**
     * Returns the parent of this channel.
     *
     * @return the parent channel.
     *         {@code null} if this channel does not have a parent channel.
     */
    Channel getParent();

    /**
     * Returns the configuration of this channel.
     */
    ChannelConfig getConfig();

    /**
     * Returns the {@link ChannelPipeline} which handles {@link ChannelEvent}s
     * associated with this channel.
     */
    ChannelPipeline getPipeline();

    /**
     * Returns {@code true} if and only if this channel is open.
     */
    boolean isOpen();

    /**
     * Returns {@code true} if and only if this channel is bound to a
     * {@linkplain #getLocalAddress() local address}.
     */
    boolean isBound();

    /**
     * Returns {@code true} if and only if this channel is connected to a
     * {@linkplain #getRemoteAddress() remote address}.
     */
    boolean isConnected();

    /**
     * Returns the local address where this channel is bound to.  The returned
     * {@link SocketAddress} is supposed to be down-cast into more concrete
     * type such as {@link InetSocketAddress} to retrieve the detailed
     * information.
     *
     * @return the local address of this channel.
     *         {@code null} if this channel is not bound.
     */
    SocketAddress getLocalAddress();

    /**
     * Returns the remote address where this channel is connected to.  The
     * returned {@link SocketAddress} is supposed to be down-cast into more
     * concrete type such as {@link InetSocketAddress} to retrieve the detailed
     * information.
     *
     * @return the remote address of this channel.
     *         {@code null} if this channel is not connected.
     *         If this channel is not connected but it can receive messages
     *         from arbitrary remote addresses (e.g. {@link DatagramChannel},
     *         use {@link MessageEvent#getRemoteAddress()} to determine
     *         the origination of the received message as this method will
     *         return {@code null}.
     */
    SocketAddress getRemoteAddress();

    /**
     * Sends a message to this channel asynchronously.    If this channel was
     * created by a connectionless transport (e.g. {@link DatagramChannel})
     * and is not connected yet, you have to call {@link #write(Object, SocketAddress)}
     * instead.  Otherwise, the write request will fail with
     * {@link NotYetConnectedException} and an {@code 'exceptionCaught'} event
     * will be triggered.
     *
     * @param message the message to write
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         write request succeeds or fails
     *
     * @throws NullPointerException if the specified message is {@code null}
     */
    ChannelFuture write(Object message);

    /**
     * Sends a message to this channel asynchronously.  It has an additional
     * parameter that allows a user to specify where to send the specified
     * message instead of this channel's current remote address.  If this
     * channel was created by a connectionless transport (e.g. {@link DatagramChannel})
     * and is not connected yet, you must specify non-null address.  Otherwise,
     * the write request will fail with {@link NotYetConnectedException} and
     * an {@code 'exceptionCaught'} event will be triggered.
     *
     * @param message       the message to write
     * @param remoteAddress where to send the specified message.
     *                      This method is identical to {@link #write(Object)}
     *                      if {@code null} is specified here.
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         write request succeeds or fails
     *
     * @throws NullPointerException if the specified message is {@code null}
     */
    ChannelFuture write(Object message, SocketAddress remoteAddress);

    /**
     * Binds this channel to the specified local address asynchronously.
     *
     * @param localAddress where to bind
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         bind request succeeds or fails
     *
     * @throws NullPointerException if the specified address is {@code null}
     */
    ChannelFuture bind(SocketAddress localAddress);

    /**
     * Connects this channel to the specified remote address asynchronously.
     *
     * @param remoteAddress where to connect
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         connection request succeeds or fails
     *
     * @throws NullPointerException if the specified address is {@code null}
     */
    ChannelFuture connect(SocketAddress remoteAddress);

    /**
     * Disconnects this channel from the current remote address asynchronously.
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         disconnection request succeeds or fails
     */
    ChannelFuture disconnect();

    /**
     * Unbinds this channel from the current local address asynchronously.
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         unbind request succeeds or fails
     */
    ChannelFuture unbind();

    /**
     * Closes this channel asynchronously.  If this channel is bound or
     * connected, it will be disconnected and unbound first.  Once a channel
     * is closed, it can not be open again.  Calling this method on a closed
     * channel has no effect.  Please note that this method always returns the
     * same future instance.
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         close request succeeds or fails
     */
    ChannelFuture close();

    /**
     * Returns the {@link ChannelFuture} which will be notified when this
     * channel is closed.  This method always returns the same future instance.
     */
    ChannelFuture getCloseFuture();

    /**
     * Returns the current {@code interestOps} of this channel.
     *
     * @return {@link #OP_NONE}, {@link #OP_READ}, {@link #OP_WRITE}, or
     *         {@link #OP_READ_WRITE}
     */
    int getInterestOps();

    /**
     * Returns {@code true} if and only if the I/O thread will read a message
     * from this channel.  This method is a shortcut to the following code:
     * <pre>
     * return (getInterestOps() & OP_READ) != 0;
     * </pre>
     */
    boolean isReadable();

    /**
     * Returns {@code true} if and only if the I/O thread will perform the
     * requested write operation immediately.  Any write requests made when
     * this method returns {@code false} are queued until the I/O thread is
     * ready to process the queued write requests.  This method is a shortcut
     * to the following code:
     * <pre>
     * return (getInterestOps() & OP_WRITE) == 0;
     * </pre>
     */
    boolean isWritable();

    /**
     * Changes the {@code interestOps} of this channel asynchronously.
     *
     * @param interestOps the new {@code interestOps}
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         {@code interestOps} change request succeeds or fails
     */
    ChannelFuture setInterestOps(int interestOps);

    /**
     * Suspends or resumes the read operation of the I/O thread asynchronously.
     * This method is a shortcut to the following code:
     * <pre>
     * int interestOps = getInterestOps();
     * if (readable) {
     *     setInterestOps(interestOps | OP_READ);
     * } else {
     *     setInterestOps(interestOps & ~OP_READ);
     * }
     * </pre>
     *
     * @param readable {@code true} to resume the read operation and
     *                 {@code false} to suspend the read operation
     *
     * @return the {@link ChannelFuture} which will be notified when the
     *         {@code interestOps} change request succeeds or fails
     */
    ChannelFuture setReadable(boolean readable);
}

 

 

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