This post originated from an RSS feed registered with Ruby Buzz
by Chris Nelson.
Original Post: API unickifying with JRuby
Feed Title: MysteryCoder
Feed URL: http://mysterycoder.blogspot.com/feeds/posts/default
Feed Description: Ramblings of secret Ruby coder in Cincinnati, OH
So I've been putting together some code examples for RubyCodeCamp in Columbus in a couple weeks. Quite awhile back I ran into a situation where I wanted to read an Excel spreadsheet from Ruby. At the time, there was no good way to do it in Ruby (MRI) and so I used Java and the nifty POI library. I thought this might be make for a nice example in JRuby. So I fired up jirb and started coding. In a few minutes I was reading data from a spreadsheet:
File.open("/home/ccnelson/documents/Invoice15.xls") do |f| workbook = HSSFWorkbook.new(IOInputStream.new(f)) puts "cell 0,0: #{workbook.getSheetAt(0).getRow(0).getCell(0).getStringCellValue}"
end
There's some nice stuff going on. I really like being able to just include a jar and start using it. Still, using the POI API in Ruby looks rather icky -- (actually, it started even worse than this, but Charles Nutter was on #jruby and was kind enough to tell me about IOInputStream). After looking at this code for a minute I started thinking and it came to me: "Hey this is Ruby. We can do anything we want!"
I started with that ugly getStringCellValue at the end. It would be nice if we could give cell a to_s and do away with that. Well, guess what, since this is Ruby, I can just open HSSFCell and do it:
File.open("/home/ccnelson/documents/Invoice15.xls") do |f| workbook = HSSFWorkbook.new(IOInputStream.new(f)) puts "cell 0,0: #{workbook.getSheetAt(0).getRow(0).getCell(0)}"
end
Cool! Even though HSSFCell is a java class, because I am using it from JRuby I can open it up and stick methods on it. This got me excited. What do I really want this API to look like? I think I'd really rather be able to access my spreadsheet cells using a simple 2 dimenional array. I mean, that's really what they are for my purposes. And guess what? In Ruby, the [] operator, like everything else in Ruby, is just a method. And if it's just a method, well I can abuse... err.. bend it to my own nefarious purposes. Bwah ha ha hah ha hah ha ha..
Oops, got a little carried away there. Ruby coding will do that sometimes. Back to the task at hand:
classHSSFSheet def [] (index) getRow index end end
classHSSFRow
def [] (index) getCell index end end File.open("/home/ccnelson/documents/Invoice15.xls") do |f| workbook = HSSFWorkbook.new(IOInputStream.new(f)) spreadsheet = workbook.getSheetAt(0) puts "cell 0,0: #{spreadsheet[0][0]}"
end
Nice! This for me is one of the killer features of JRuby. A lot of scripting languages will let you access the Java APIs in a more light weight language. But because of the features of the Ruby language, it becomes so easy to modify APIs to suit your needs, desires, and insane urges.
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