Step by Step-Turning Ruby Files into Java Classes

以前做了个Ruby的项目，最近有了点新的需求，其中有一条是要保护源代码，我选择用JRuby把rb文件编译为class，查了些资料，看了下jrubyc相关的一些代码，也许有朋友有类似的需要，和大家分享一下。突发奇想用英文来写，很久不写英文了，果然这个还得常写写。。。附上对应的中文，如果不高兴看英文的同学可以直接看中文的，呵呵。

 

There are many reasons for us to turn Ruby files (.rb) into Java classes (.class). For example, you want a high-performance system, or you want to protect your ruby code, etc. Last year, JRuby finished its compiler which can help you to do the compilation. Now you’ve got another choice besides XRuby. You can find some material on JRuby’s Wiki, but it’s far from enough, and the most pages you find on the Internet just compile some hello world programs. I tried to compile my ruby project (of course, it's more complex than printing "Hello World", it's a network traffic control script under FreeBSD) last week. If you have the same requirement, maybe my experience can give you a little help :-)
The first question is how to start the compiler. The Wiki just tells us to use "jrubyc". Actually, there's no jrubyc.bat or jubyc.exe in bin at all. So, if you are using Windows like me, you should start the script jrubyc manually. For example:

jruby %JRUBY_HOME%\bin\jrubyc <rb>

Suppose your program is very simple, please forgive me using "Hello World" again. (src\hello.rb)

p "Hello World"

The command to compile it looks like this:

jruby %JRUBY_HOME%\bin\jrubyc src\hello.rb

Then, try this one to run it:

java -cp .;%JRUBY_HOME%\lib\jruby.jar ruby.src.hello

Have you feel something strange? Why the class is ruby.src.hello? After checking the command line parameters, you will find the answer. Here is the command pattern:

jrubyc [options] (FILE|DIRECTORY)

jrubyc has three parameters:

-d,--dir DIR	Use DIR as the root of the compiled package and filename
-p,--prefix PREFIX	Prepend PREFIX to the file path and package. "ruby" is default
-t,--target TARGET	Output files to TARGET directory

Now, try to compile the hello.rb again:

jruby %JRUBY_HOME%\bin\jrubyc -d src -p "" src\hello.rb
java -cp .;%JRUBY_HOME%\lib\jruby.jar hello

Next, find yourself some other Ruby files which have require or include or something else. Put them into a directory. Let's call it dir. Try the following command:

md classes
jruby %JRUBY_HOME%\bin\jrubyc -t classes -d dir -p "" dir

If everything goes right, you can check the classes directory. All the files are there. Since you require something outside the source files, don’t forget to tell java where to find them. For example, your dir\complex_ruby_script required yaml.

java -cp .\classes;%JRUBY_HOME%\lib\jruby.jar;%JRUBY_HOME%\lib\ruby\1.8 complex_ruby_script

You should see the result of your Ruby program. Maybe I should say your Java program.

That's all. If you want to compile your Rails project so as to deploy it into a Java EE application server, please check out GoldSpike and Warbler.