More specifically I would like to embed an XML document.
The idea is either to display the XML in a text pane of some sort or have an icon which would open the XML document with the default system editor (Notepad, IE, XML Spy or whatnot). What I am looking for is what you get when you in Excel choose Insert -> Object... and then choose the Create from file tab adding the file you want included.
There is support for reading embedded files using the methods
XSSFWorkbook getAllEmbedds
HSSFWorkbook getAllEmbeddedObjects
... but I cannot find anything similar for writing.
I get a feeling I should be able to add an embedded object by creating an entry in the POI Filesystem and then link to it in a as you would do for a picture, but I cannot figure out how.