核心的概念

Netty的异步事件驱动模型主要涉及到下面几个核心的概念:

  • Channel:表示一个与socket关联的通道
  • ChannelPipeline: 管道,一个Channel拥有一个ChannelPipeline,ChannelPipeline维护着一个处理链(严格的说是两个:upstream、downstream),处理链是由很多处理句柄ChannelHandler所构成,每个ChannelHandler处理完以后会传递给链中的下一个处理句柄继续处理。
  • ChannelHandler:处理句柄,用户可以定义自己的处理句柄来处理每个请求,或发出请求前进行预处理,典型的有编码/解码器:decoder、encoder。
  • ChannelEvent:事件,是整个模型的处理对象,当产生或触发(fire)一个事件时,该事件会沿着ChannelPipeline处理链依次被处理。
  • ChannelFuture: 异步结果,这个是异步事件处理的关键,当一个事件被处理时,可以直接以ChannelFuture的形式直接返回,不用在当前操作中被阻塞。可以通过 ChannelFuture得到最终的执行结果,具体的做法是在ChannelFuture添加监听器listener,当操作最终被执行完 后,listener会被触发,我们可以在listener的回调函数中预定义我们的业务代码。
  • EventLoopGroup:事件循环组,
  • EventExecutorGroup(接口):继承自java并发包ScheduledExecutorService,执行定时任务,只要使用其next()方法
  • BootStrap:启动辅助类,

Channel

Channel

ChannelPipeline

Channel

ChannelFuture && ChannelPromise

  • ChannelFuture: The result of an asynchronous Channel I/O operation.
  • ChannelPromise: Special ChannelFuture which is writable.

Channel

NioEventLoop.png

  • EventExecutorGroup: The EventExecutorGroup is responsible for providing the EventExecutor’s to use via its next() method. Besides this, it is also responsible for handling their life-cycle and allows shutting them down in a global fashion.
  • EventExecutor: The EventExecutor is a special EventExecutorGroup which comes with some handy methods to see if a Thread is executed in a event loop. Besides this, it also extends the EventExecutorGroup to allow for a generic way to access methods.
  • EventLoopGroup: Special EventExecutorGroup which allows registering Channels that get processed for later selection during the event loop.

Channel

NioEventLoopGroup

Channel

SimpleChannelInboundHandler

Channel

参考资料