Error on creating war using warbler

i have开发者_如何转开发 a jruby application, and use warbler to make war files of it. But everytime i ran jruby -S rake war The warbler throw an error, it said can't convert nil to String and the error is in rubyzip, it happened when rake invoked war:jar, so how can i fix it ?

do we have any other alternative to create war for jruby ? (beside the warbler)

below is what i had on my system.

jruby -version
jruby 1.3.0 (ruby 1.8.6p287) (2009-06-03 5dc2e22) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_20) [x86_64-java]

actionmailer (2.0.2)
actionpack (2.0.2)
activerecord (2.0.2)
activeresource (2.0.2)
activesupport (2.0.2)
gemcutter (0.5.0)
jruby-jars (1.5.1)
jruby-memcache-client (1.7.0)
jruby-rack (1.0.1)
json_pure (1.4.3)
rails (2.0.2)
rake (0.8.7)
rspec (1.2.6)
rubyzip (0.9.4)
sources (0.0.1)
warbler (1.1.0)

$: jruby -S rake war
** Invoke war (first_time)
** Execute war
** Invoke war:files (first_time)
** Execute war:files
** Invoke war:jar (first_time)
** Execute war:jar
rm -f prog.war
Creating prog.war
rake aborted!
can't convert nil into String
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1113:in `<<`
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rubyzip-0.9.4/lib/zip/zip.rb:1062:in `<<`
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rubyzip-0.9.4/lib/zip/ioextras.rb:125:in 
....
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:31
/Users/suprie/Opt/jruby/lib/ruby/gems/1.8/gems/rake-0.8.7/bin/rake:19:in `load'
/Users/suprie/Opt/jruby/bin/rake:19