Question: `DataServiceRequestException` was unhandled by user code. An error occurred while processing this request.

This is in relation to the previous post I added 

```
public void AddEmailAddress(EmailAddressEntity emailAddressTobeAdded)
{
    AddObject("EmailAddress", emailAddressTobeAdded);
    SaveChanges();
}

```

Again the code breaks and gives a new exception this time. Last time it was Storage Client Exception, now it is `DataServiceRequestException`. Code breaks at `SaveChanges`.

Answer: 
I was looking into implementing something like this a few month ago.  

Since GWT compiles your code to JavaScript there is no way for you to do that on the client side, JavaScript can't access the file system.  

So you would need to upload the file to the server first and do the conversion on the server side and send the converted file back.  

I have never heard of JODConverter before, the the library I wanted to use was [Apache POI](http://poi.apache.org/index.html) . Unfortunately I can't tell you anything about it, because I haven't tried it yet.
GWT is mostly a client side toolkit. Are you trying to make a tool that does all the conversion on the client side, with no help from the server? In that case, you should be looking for JavaScript libraries that can read/convert all those formats. If you are planning to have the user upload their files to the server, then you can use whatever technology you want on the server, and just use GWT for the UI.