ChannelHandlerContext的writeAndFlush方法会将数据写到ChannelPipeline中当前ChannelHandler的下一个ChannelHandler开始处理。
ChannelHandlerContext#writeAndFlush实现源码：
private void write(Object msg, boolean flush, ChannelPromise promise) { AbstractChannelHandlerContext next = findContextOutbound(); final Object m = pipeline.touch(msg, next); EventExecutor executor = next.executor(); if (executor.inEventLoop()) { if (flush) { next.invokeWriteAndFlush(m, promise); } else { next.invokeWrite(m, promise); } } else { AbstractWriteTask task; if (flush) { task = WriteAndFlushTask.newInstance(next, m, promise); } else { task = WriteTask.newInstance(next, m, promise); } safeExecute(executor, task, promise, m); } } private AbstractChannelHandlerContext findContextOutbound() { AbstractChannelHandlerContext ctx = this; do { ctx = ctx.prev; } while (!ctx.outbound); return ctx; }Channel的writeAndFlush方法会将数据写到ChannelPipeline中最后一个ChannelHandler然后数据从尾部开始向头部方向流动会经过所有的ChannelHandler, ChannelPipeline中的所有ChannelHandler都可以处理数据。
public final ChannelFuture writeAndFlush(Object msg) { return tail.writeAndFlush(msg); }