private void setEventHandler(NioHandler eventHandler) {
        if (eventHandler == null) {
            eventHandler = new EmptyHandler();
        }
        this.eventHandler = eventHandler;
    }
@author Robert HG (254963746@qq.com) on 1/9/16.
lts-core/src/main/java/com/github/ltsopensource/nio/NioServer.java