-
-
Notifications
You must be signed in to change notification settings - Fork 923
Loading Scripts From Classpath
In addition to the usual Ruby load path, JRuby also supports loading scripts from any jar file or system path added to the JVM's class path (or "classpath").
$ cat file.rb
puts "File is: #{__FILE__}"
$ jar cvf file.jar file.rb
added manifest
adding: file.rb(in = 14) (out= 16)(deflated -14%)
$ jruby -J-cp file.jar uri:classloader:/file.rb
File is: uri:classloader:/file.rb
$ jruby -e 'require "./file.jar"; require "uri:classloader:/file"'
File is: uri:classloader:/file.rb
$ jruby -e '$CLASSPATH << "./file.jar"; require "uri:classloader:/file.rb"'
uri:classloader:/file.rb
$ java -cp jruby-complete.jar:file.jar org.jruby.Main uri:classloader:/file.rb
File is: uri:classloader:/file.rb
Files in the classpath live within the "uri:classloader" URI namespace, with the entire namespace being treated as a second virtual filesystem root. Under most circumstances, you can chdir into these paths and JRuby will simulate running from that filesystem (process-launching and other system-level operations must still use the actual user current directory).
$ jruby -e 'require "./file.jar"; Dir.chdir "uri:classloader:/"; require "./file"'
File is: uri:classloader:/file.rb
This also affects how require_relative works, since a classpath resource lives under a separate hierarchy of path elements (note that we are not including file.jar here, so file.rb lives only in the normal system current directory):
$ cat relative.rb
require_relative 'file'
$ jar cvf relative.jar relative.rb
...
$ java -cp jruby-complete.jar:relative.jar org.jruby.Main uri:classloader:/relative.rb
LoadError: no such file to load -- uri:classloader:/file
require at org/jruby/RubyKernel.java:974
require_relative at org/jruby/RubyKernel.java:1002
<main> at uri:classloader:/relative.rb:1
To allow require_relative to work from within the uri:classloader namespace, be sure to include the files you wish to load relatively on the classpath in some way:
$ java -cp lib/jruby-complete.jar:relative.jar:. org.jruby.Main uri:classloader:/relative.rb
File is: uri:classloader:/file.rb
$ java -cp lib/jruby-complete.jar:relative.jar:file.jar org.jruby.Main uri:classloader:/relative.rb
File is: uri:classloader:/file.rb
JRuby's ability to load, require, and require_relative Ruby scripts from entirely within the classpath namespace makes it possible for you to jar up entire applications and their dependencies, distributing a single file you can run on any JVM. See tools like Warbler for help assembling larger applications into jar or war (web application archive) files.