BI Beans only provides export to CSV to be imported into Excel, at least up to the 9.0.4 release:
News from the BI Beans product team:
In the 9.0.5 release of BI Beans, export to Excel is native feature. It maintains all formatting and has options for how logical pages are exported (i.e. as separate Excel sheets.
See this post by Mark Ritmann with a reference to a Java to Excel open source project: Java Excel API project. It allows developers to read Excel spreadsheets, and to generate Excel spreadsheets dynamically. In addition, it contains a mechanism which allows java applications to read a spreadsheet, modify cells, and write the new spreadsheet.
The following post on OTN describes the Java code to export BI Bean Cross Tab data to be used with Java Excel API: How to Export the BI Beans report to Excel sheet?
Another framework for Java-to-Excel of course is Apache POI - which tries to do the same thing. Both seem to offer only a Java API, not an XML to Excel transformation. Although POI with Cocoon maybe can do something along those lines. See this introductory article to POI: Excel Reports with Apache Cocoon and POI by Steve Punte (2003)
Oracle will shortly announce an Excel plugin that will support OLAP operations. BI Beans technology is underlying this plugin too. I am not sure whether BI Beans defined for a Web Application can somehow be applied to this plugin as well. The following description comes from Vlamis Software:
Discoverer for OLAP is an ad-hoc query tool that is built in BI Beans. It allows a user to browse through 9iOLAP cubes (ROLAP star schemas and MOLAP analytic workspaces). It is built in BI Beans and exposes much of the power of BI Beans in a pre-built application.
The “spreadsheet add-in” allows Excel to run BI Beans against 9iOLAP cubes. In effect, Excel serves as the “middle-ware”, launching the BI Beans query wizard and the calculation wizard. The results are then dropped into an Excel spreadsheet, along with drill-down and paging capability. If you users require direct access to their data from Excel, you will be interested in this tool. No more exporting to Excel–access your entire OLAP cube directly!