剖析Netty之底层原理(三)

神秘北极圈 阿拉斯加的山巅

谁的脸出现海角的天边

忽然的瞬间在那遥远的地点

我看见恋人幸福的光点

灵魂在招唤唱着古老

陌生熟悉的歌谣 天空 在微笑

我的世界缤纷闪耀

前面浑浑噩噩的把服务端的实现底层源码来了个大致，感觉头有点大，这里用图例的方式来理下思绪。

一、EventLoopGroup bossGroup = new NioEventLoopGroup();

这是服务端的第一句代码，类似的还new了一个workGroup，工作线程组

这两句代码，Netty底层的各种初始化动作，前面也都说过了，这里做个总结：

底层逐步初始化调用程序如下图：

其类调用时序图如下所示

这里，需要重点看下

io.netty.util.concurrent.MultithreadEventExecutorGroup#MultithreadEventExecutorGroup

(int, 

java.util.concurrent.Executor,

io.netty.util.concurrent.EventExecutorChooserFactory, java.lang.Object...

)方法

源码如下：

protected MultithreadEventExecutorGroup(int nThreads, Executor executor,                                            EventExecutorChooserFactory chooserFactory, Object... args) {                //当线程数没有的时候，抛出异常，根据前面分析，这里的线程数为服务器内核数量*2        if (nThreads <= 0) {            throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));        }
        //这里的Executor是null,所以初始化一个        if (executor == null) {            //初始化一个类型是io.netty.util.concurrent.ThreadPerTaskExecutor的线程池            //线程池类型为io.netty.util.concurrent.DefaultThreadFactory            executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());        }
        // 设置事件驱动数组，大小根据设定或者默认的来        children = new EventExecutor[nThreads];
        for (int i = 0; i < nThreads; i ++) {            boolean success = false;            try {                //设定每个事件驱动数组为io.netty.channel.nio.NioEventLoop                //这里调用的newChild,下面会有详细解释                children[i] = newChild(executor, args);                success = true;            } catch (Exception e) {                // TODO: Think about if this is a good exception type                throw new IllegalStateException("failed to create a child event loop", e);            } finally {                if (!success) {                    for (int j = 0; j < i; j ++) {                        //如果添加失败，则关闭每一个io.netty.channel.nio.NioEventLoop                        children[j].shutdownGracefully();                    }
                    for (int j = 0; j < i; j ++) {                        EventExecutor e = children[j];                        try {                            while (!e.isTerminated()) {                                e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);                            }                        } catch (InterruptedException interrupted) {                            // Let the caller handle the interruption.                            Thread.currentThread().interrupt();                            break;                        }                    }                }            }        }
        //初始化io.netty.util.concurrent.EventExecutorChooserFactory.EventExecutorChooser        //其结果值为io.netty.util.concurrent.DefaultEventExecutorChooserFactory.PowerOfTwoEventExecutorChooser#PowerOfTwoEventExecutorChooser        //或者io.netty.util.concurrent.DefaultEventExecutorChooserFactory.GenericEventExecutorChooser#GenericEventExecutorChooser        chooser = chooserFactory.newChooser(children);
        final FutureListener