Jxcell is a high performance spreadsheet component for java
development environments that enables you to create, manipulate, and
print excel worksheets,it was writen in pure java code.
Jxcell directly access excel biff record, support formulae, images,
lines, charts.
Jxcell can act as a rapid serverside caculation engine and support
over 260 excel functions.
Jxcell can be embedded in small plug-in(java applet) or be using in
Java desktop client side applications.

In 2.0,Jxcell can read excel with excel 2003's SpreadsheetML format
and excel 2007's OpenXML format.

http://www.jxcell.net