Our app sells to the finance vertical, so we deliver a lot of data in Excel. There is a really great project called Apache POI that does just what we need. Yes, there is also the Ruby spreadsheet gem, but while the gem itself works fine most of the time, the underlying reverse-engineering of the BIFF8 (Excel 97-2000) format is sketchy at best. Spreadsheets generated with the spreadsheet gem don't behave as expected in Excel. For example, if you click the '%' format button, you get an error message. This ends up making our product look unpolished.
This kind of turned in to a spreadsheet gem rant, but if you step back, it's typical of a greater problem. The Ruby community is relatively small when compared with the Java community. It's also significantly less "enterprisey". This means that you'll see a lot of effort put in to things that developers like -- clever libraries, syntactic "sugar", etc -- but you're less likely to see mature libraries like Apache POI. Who the hell wants to sit around and figure out BIFF8, anyway? A lot of the enterprise stuff just isn't fun, but there are plenty of Java devs who get paid to do it for their day jobs.
This kind of turned in to a spreadsheet gem rant, but if you step back, it's typical of a greater problem. The Ruby community is relatively small when compared with the Java community. It's also significantly less "enterprisey". This means that you'll see a lot of effort put in to things that developers like -- clever libraries, syntactic "sugar", etc -- but you're less likely to see mature libraries like Apache POI. Who the hell wants to sit around and figure out BIFF8, anyway? A lot of the enterprise stuff just isn't fun, but there are plenty of Java devs who get paid to do it for their day jobs.
By using JRuby, you can benefit from both worlds.