FileReference and registerClassAlias

Question

Hello,

I'm trying to use the native flex serialization/deserialization process to save/load state of a workspace in flex. In order to save or load a file I have to use my servlet, which just bounces back the bytes from the input stream to the output stream. Here's a basic outline of my Flex code:

Serialized Object Container:

public class MyWorkspace {
    public var id : String;
    public var url : String;
    public var objectCollection : ArrayCollection; // Contains MySubObjects
}

Serialized sub object:

public class MySubObject
{
    public var name:String;
    public var csv:String;
}

Visual Element Constructor:

public function VisualSandbox(){
    registerClassAlias("MyWorkspaceAlias", MyWorkspace);
    registerClassAlias("MySubObjectAlias", MySubObject);
}

Visual Element Event Handlers:

public function onSaveButtonClick(event : MouseEvent) : void
{
    var ws : MyWorkspace = new MyWorkspace();
    ws.id = "ID";
    ws.url = "URL";
    ws.objectCollection = new ArrayCollection(veObjCollectionAC.source.slice());

    var ba : ByteArray = new ByteArray();
    ba.writeObject(ws);
    ba.position = 0;

    var fr : FileReference = new FileReference();
    // There's no need for me to put the rest so 
    ...
    fr.download(urlRequest, "workspace.ws");
}

public function onLoadButtonClick(event : MouseEvent) : void
{
    veFileReference = new FileReference();
    veFileReference.addEventListener(DataEvent.UPLOAD_COMPLETE_DATA, loadCompleteHandler);
    // This part works as well so I'm skipping it.

}

public function loadCompleteHandler(event : DataEvent) : void
{
    // Pretend I loaded "workspace.ws" by bouncing it off of my servlet byte for byte.
    var ba : ByteArray = new ByteArray();
    ba.writeObject(event.data);
    ba.position = 0;
    var obj : * = ba.readObject();
    trace(obj is MyWorkspace); // Prints false
}

So my problem here is not with the saving of the workspace. That works great. My problem is with the loading of a workspace. The event.data that I write to the byte array is not reconstituted into a MyWorkspace object even though it is exactly what I wrote to the file.

There has to be a way of making a MyWorkspace object from the data, but I can't figure it out. Has anyone tried to do this before?

Thanks!

Answer 1

Have you tried casting the value?

    var obj : MyWorkspace = ba.readObject() as MyWorkspace;

Answer 2

I've figured out what the problem here is. It specifically has to do with the line:

ba.writeObject(event.data);

The data field of the event, being a DataEvent, is specifically of type String. ByteArray.writeObject() puts a type code at the beginning of the byte array. This took me many hours of looking at Hexplorer to figure out why, exactly, the byte array had 2-3 extra characters at its beginning.

My current best solution for this is to change that line as follows:

for (var i : int = 0; i < event.data.length; ++i)
{
    ba.writeByte(event.data.charCodeAt(i));
}

This ensures that the byte array is exactly the same as what was saved to my local drive and bounced off my servlet.

After doing this, trace(obj is MyWorkspace) prints true.

Hope this helps someone else in the future!