扩展ArrayCollection会导致远程处理失败

Question

我需要在Flex中扩展一个ArrayCollection来实现this之类的东西。但是当我将它发送到服务器时，似乎序列化失败了。

ArgumentError: Error #2004: One of the parameters is invalid.
    at ObjectOutput/writeObject()
    at mx.collections::ArrayList/writeExternal()[E:\dev\4.x\frameworks\projects\framework\src\mx\collections\ArrayList.as:595]
    at mx.collections::ArrayCollection/writeExternal()[E:\dev\4.x\frameworks\projects\framework\src\mx\collections\ArrayCollection.as:159]
    at flash.net::NetConnection/invokeWithArgsArray()
    at flash.net::NetConnection/call()
    at mx.messaging.channels::NetConnectionChannel/internalSend()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\channels\NetConnectionChannel.as:276]
    at mx.messaging.channels::AMFChannel/internalSend()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\channels\AMFChannel.as:364]
    at mx.messaging::Channel/send()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\Channel.as:1013]
    at mx.messaging.channels::PollingChannel/send()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\channels\PollingChannel.as:365]
    at mx.messaging::ChannelSet/send()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\ChannelSet.as:1424]
    at mx.messaging::MessageAgent/internalSend()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\MessageAgent.as:1263]
    at mx.messaging::Producer/internalSend()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\Producer.as:171]
    at mx.messaging::AbstractProducer/send()[E:\dev\4.x\frameworks\projects\rpc\src\mx\messaging\AbstractProducer.as:561]
    at mx.rpc::AsyncRequest/invoke()[E:\dev\4.x\frameworks\projects\rpc\src\mx\rpc\AsyncRequest.as:153]
    at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::invoke()[E:\dev\4.x\frameworks\projects\rpc\src\mx\rpc\AbstractInvoker.as:379]
    at mx.rpc.remoting::Operation/http://www.adobe.com/2006/flex/mx/internal::invoke()[E:\dev\4.x\frameworks\projects\rpc\src\mx\rpc\remoting\Operation.as:287]
    at mx.rpc.remoting::Operation/send()[E:\dev\4.x\frameworks\projects\rpc\src\mx\rpc\remoting\Operation.as:254]
    at Function/http://adobe.com/AS3/2006/builtin::apply()
    at mx.rpc::AbstractService/http://www.adobe.com/2006/actionscript/flash/proxy::callProperty()[E:\dev\4.x\frameworks\projects\rpc\src\mx\rpc\AbstractService.as:408]

有什么方法可以解决这个问题吗？

详细信息：使用Flex 4.1，使用BlazeDS和Java

这是扩展类：

package 
{
    import mx.collections.ArrayCollection;

    public class NewEntryArrayCollection extends ArrayCollection
    {
        private var newEntry:Object;

        // callback to generate a new entry
        public var factoryFunction:Function;

        // callback to test if an entry is empty and should be deleted
        public var emptyTestFunction:Function;

        public function NewEntryArrayCollection(source:Array=null)
        {
            super(source);
        }

        override public function getItemAt(index:int, prefetch:int=0):Object
        {
            if (index < 0 || index >= length)
                throw new RangeError("invalid index", index);

            if (index < super.length)
                return super.getItemAt(index, prefetch);

            if (!newEntry)
                newEntry=factoryFunction();
            return newEntry;
        }

        override public function get length():int
        {
            return super.length + 1;
        }

        override public function itemUpdated(item:Object, property:Object=null, oldValue:Object=null, newValue:Object=null):void
        {
            super.itemUpdated(item, property, oldValue, newValue);
            if (item != newEntry)
            {
                if (emptyTestFunction != null)
                {
                    if (emptyTestFunction(item))
                    {
                        removeItemAt(getItemIndex(item));
                    }
                }
            }
            else
            {
                if (emptyTestFunction != null)
                {
                    if (!emptyTestFunction(item))
                    {
                        newEntry=null;
                        addItemAt(item, length - 1);
                    }
                }
            }
        }
    }
}