Netty源码二：服务端创建NioEventLoopGroup

示例

还是拿之前启动源码的示例，来分析NioEventLoopGroup源码

NioEventLoopGroup构造函数

这里能看到会调到父类的MultiThread EventLoopGroup的构造方法

MultiThreadEventLoopGroup

这里我们能看到，如果传入的线程数目为0，那么就会设置2倍的核心的线程数目
接着，继续会调用父类的MultithreadEventExecutorGroup的构造方法

MultiThreadEventExecutorGroup

// todo 在这个构造方法中,完成了一些属性的赋值, 彻底构造完成  事件循环组对象
// todo  Object... args  是 selectorProvider, selectStrategyFactory, RejectedExecutionHandlers.reject()的简写
protected MultithreadEventExecutorGroup(int nThreads, Executor executor,EventExecutorChooserFactory chooserFactory, Object... args) {if (nThreads <= 0) {throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));}if (executor == null) {// todo 下面需要的参数,一开始使用无参的构造方法时, 传递进来的 就是null ,执行这一行代码, 创建默认的线程工厂// todo ThreadPerTaskExecutor  意味为当前的事件循环组   创建Executor , 用于 针对每一个任务的Executor   线程的执行器// todo  newDefaultThreadFactory根据它的特性,可以给线程加名字等,// todo 比传统的好处是 把创建线程和 定义线程需要做的任务分开, 我们只关心任务,  两者解耦// todo 每次执行任务都会创建一个线程实体// todo NioEventLoop 线程命名规则  nioEventLoop-1-XX    1代表是第几个group   XX第几个eventLoopexecutor = new ThreadPerTaskExecutor(newDefaultThreadFactory());}// todo children是线程执行器组里面的线程执行器children = new EventExecutor[nThreads];// todo  循环实例化for (int i = 0; i < nThreads; i++) {boolean success = false;try {// todo 创建EventLoop, 直接看一下这个newChild , 它的返回值是 EventExecutor , 但是如果我们直接去看它子类的实现的话// todo 会发现new 的实例其实的 NioEventLoop, 这并不奇怪, 因为,NioEventLoop间接实现了 EventExecutor 接口// todo 换句话说, 其实就是 NioEventLoop 就是 拥有线程执行器的功能children[i] = newChild(executor, args);success = true;} catch (Exception e) {// TODO: Think about if this is a good exception typethrow new IllegalStateException("failed to create a child event loop", e);} finally {if (!success) {for (int j = 0; j < i; j++) {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;}}}}}// todo chooser 在这里 初始化了chooser = chooserFactory.newChooser(children);final FutureListener<Object> terminationListener = new FutureListener<Object>() {@Overridepublic void operationComplete(Future<Object> future) throws Exception {if (terminatedChildren.incrementAndGet() == children.length) {terminationFuture.setSuccess(null);}}};for (EventExecutor e : children) {e.terminationFuture().addListener(terminationListener);}Set<EventExecutor> childrenSet = new LinkedHashSet<EventExecutor>(children.length);Collections.addAll(childrenSet, children);readonlyChildren = Collections.unmodifiableSet(childrenSet);
}