NioEventLoop源码之openSelector优化

构造函数

NioEventLoop(NioEventLoopGroup parent, Executor executor, SelectorProvider selectorProvider,
                 SelectStrategy strategy, RejectedExecutionHandler rejectedExecutionHandler) {
        super(parent, executor, false, DEFAULT_MAX_PENDING_TASKS, rejectedExecutionHandler);
        if (selectorProvider == null) {
            throw new NullPointerException("selectorProvider");
        }
        if (strategy == null) {
            throw new NullPointerException("selectStrategy");
        }
        provider = selectorProvider;
        final SelectorTuple selectorTuple = openSelector(); //SelectorProvider.provider().openSelector()
        selector = selectorTuple.selector; // SelectedSelectionKeySetSelector  包装unwrappedSelector
        unwrappedSelector = selectorTuple.unwrappedSelector; //原始的nio创建对象  比如WindowsSelectorImpl
        selectStrategy = strategy; // DefaultSelectStrategy
    }

openSelector 优化

private SelectorTuple openSelector() {
        final Selector unwrappedSelector;
        try {
            unwrappedSelector = provider.openSelector(); //创建java原生selector
        } catch (IOException e) {
            throw new ChannelException("failed to open a new selector", e);
        }
        //是否需要优化，默认需要DISABLE_KEYSET_OPTIMIZATION=false
        if (DISABLE_KEY_SET_OPTIMIZATION) {
            return new SelectorTuple(unwrappedSelector);
        }
        //尝试获取sun.nio.ch.SelectorImpl的class对象
        Object maybeSelectorImplClass = AccessController.doPrivileged(new PrivilegedAction