RSL（包括ResourceModule）是并发被加载的还是顺序被加载的？ --

RSL不只一个，这些RSL被Flex框架串行加载，即加载完一个后再加载下一个。

?

>>源代码片断佐证： mx.core.RSLListLoader.as

package mx.core
{

?//构造函数，调用函数loadNext()加载第一个RSL
??public function load(progressHandler:Function,
????????????????????? completeHandler:Function,
????????????????????? ioErrorHandler:Function,
????????????????????? securityErrorHandler:Function,
????????????????????? rslErrorHandler:Function):void
??? {
??? ?chainedProgressHandler = progressHandler;
???? chainedCompleteHandler = completeHandler;
???? chainedIOErrorHandler = ioErrorHandler;
???? chainedSecurityErrorHandler = securityErrorHandler;
???? chainedRSLErrorHandler = rslErrorHandler;
????
???? currentIndex = -1; // so first loaded item will be index 0
???? loadNext();
????????
??? }
????

??? //加载RSL
??? private function loadNext():void
??? {
??????? if (!isDone())
??????? {
??????????? currentIndex++;

???????? // Load the current RSL.
???????? if (currentIndex < rslList.length)
???????? {
???????????? // Load rsl and have the RSL loader chain the
???????????? // events our internal events handler or the chained
???????????? // events handler if we don't care about them.
???????????? rslList[currentIndex].load(chainedProgressHandler,
??????????????????????????????????????? listCompleteHandler,
??????????????????????????????????????? listIOErrorHandler,
??????????????????????????????????????? listSecurityErrorHandler,
??????????????????????????????????????? chainedRSLErrorHandler);
???????? }
??????? }
??? }

?

? //一个RSL加载完毕后，再加载下一个????
?private function listCompleteHandler(event:Event):void
??? {
??????? // Pass event to external listener.
??????? if (chainedCompleteHandler != null)
??????????? chainedCompleteHandler(event);

??????? // Load the next RSL.
??????? loadNext();
??? }

}

?

========================================================================

>>猜测：为什么不采用并发下载？

（1）。FlashPlayer的并发下载功能有缺陷，造成并发下载的时候会莫名出现问题。

???????? 参考： 《同时new了多个URLLoader 加载文件时所遇到的问题》

??????????????????? http://bbs.9ria.com/thread-88518-1-1.html

（2）。http协议中对客户端请求连接数的限制

???????? 参考： 《IE并发连接限制(as)AS队列加载类（as3和as2）》

??????????????????? http://kb.cnblogs.com/a/1583038/??

???????? 参考： 《“HTTP协议对客户端并发连接数目的限制” vs “Flex并行上传或下载” 》

??????????????????? http://www.voidcn.com/article/p-wzvobwfl-bdn.html

（3）。基于（2），代码形式上并行了，但其本质不过是有限数量的并发连接，剩下的连接处于等待状态而已。