app engine modify xml

I am writing a GWT app running on App 开发者_开发百科Engine, which needs to modify a XML File serverside. As far as I know there is no way to modify a XML file in the WAR directory or any subdirectories. What other possibilities do I have to store that data? Can I use the Data Store somehow or should I look for storage space somewhere else and access it there (if so any recommendations?)?

Any help is appreciated!

---

You can store the XML in the datastore as either a text or string property.

Less than or equal to 500 characters in length:

StringProperty

Greater than 500 characters in length:

TextProperty