netty源碼分析 之四 transport(ChannelPipeline)

前面看了channel定義，以及接口定義，可知道實作類。

*                                                 I/O Request
 *                                            via {@link Channel} or
 *                                        {@link ChannelHandlerContext}
 *                                                      |
 *  +---------------------------------------------------+---------------+
 *  |                           ChannelPipeline         |               |
 *  |                                                  \|/              |
 *  |    +----------------------------------------------+----------+    |
 *  |    |                   ChannelHandler  N                     |    |
 *  |    +----------+-----------------------------------+----------+    |
 *  |              /|\                                  |               |
 *  |               |                                  \|/              |
 *  |    +----------+-----------------------------------+----------+    |
 *  |    |                   ChannelHandler N-1                    |    |
 *  |    +----------+-----------------------------------+----------+    |
 *  |              /|\                                  .               |
 *  |               .                                   .               |
 *  | ChannelHandlerContext.fireIN_EVT() ChannelHandlerContext.OUT_EVT()|
 *  |          [method call]                      [method call]         |
 *  |               .                                   .               |
 *  |               .                                  \|/              |
 *  |    +----------+-----------------------------------+----------+    |
 *  |    |                   ChannelHandler  2                     |    |
 *  |    +----------+-----------------------------------+----------+    |
 *  |              /|\                                  |               |
 *  |               |                                  \|/              |
 *  |    +----------+-----------------------------------+----------+    |
 *  |    |                   ChannelHandler  1                     |    |
 *  |    +----------+-----------------------------------+----------+    |
 *  |              /|\                                  |               |
 *  +---------------+-----------------------------------+---------------+
 *                  |                                  \|/
 *  +---------------+-----------------------------------+---------------+
 *  |               |                                   |               |
 *  |       [ Socket.read() ]                    [ Socket.write() ]     |
 *  |                                                                   |
 *  |  Netty Internal I/O Threads (Transport Implementation)            |
 *  +-------------------------------------------------------------------+
           

在看下接口方法

ChannelPipeline 主要是 inbound和outbound方法

inbound方法一般是内部定義的模闆方法，繼承實作之後就期待調用即可

outbound方法一般是對方提供api接口，比如bind connect read write等

DefaultChannelPipeline

然後我們看下channelPipeline的實作類，如何構造pipe的

final AbstractChannel channel;

    final AbstractChannelHandlerContext head;
    final AbstractChannelHandlerContext tail;

    private final Map<String, AbstractChannelHandlerContext> name2ctx =
            new HashMap<String, AbstractChannelHandlerContext>(4);

    /**
     * @see #findInvoker(EventExecutorGroup)
     */
    private Map<EventExecutorGroup, ChannelHandlerInvoker> childInvokers;

    DefaultChannelPipeline(AbstractChannel channel) {
        if (channel == null) {
            throw new NullPointerException("channel");
        }
        this.channel = channel;

        tail = new TailContext(this);
        head = new HeadContext(this);

        head.next = tail;
        tail.prev = head;
    }
           

關鍵的兩個類tailContext和headcontext,這樣的話就扯出我們下一個接口   ChannelHandler