从 JRuby 调用 Java 类时出现问题

我正在尝试使用锅炉管 http://code.google.com/p/boilerpipe/wiki/QuickStart来自 JRuby。我见过guide https://github.com/jruby/jruby/wiki/CallingJavaFromJRuby用于从 JRuby 调用 Java，并已成功地将其与另一个 Java 包一起使用，但无法弄清楚为什么同样的东西不能与样板一起工作。

我正在尝试基本上从 JRuby 执行与 Java 相同的操作：

URL url = new URL("http://www.example.com/some-location/index.html");
String text = ArticleExtractor.INSTANCE.getText(url);

在 JRuby 中尝试过：

require 'java'
url = java.net.URL.new("http://www.example.com/some-location/index.html")
text = Java::DeL3sBoilerpipeExtractors::ArticleExtractor.INSTANCE.getText(url)

这是基于API Java文档 http://boilerpipe.googlecode.com/svn/trunk/boilerpipe-core/javadoc/1.0/index.html用于锅炉管。这是错误：

jruby-1.6.0 :042 > Java::DeL3sBoilerpipeExtractors::ArticleExtractor
NameError: cannot load Java class deL3sBoilerpipeExtractors.ArticleExtractor
        from org/jruby/javasupport/JavaClass.java:1195:in `for_name'
        from org/jruby/javasupport/JavaUtilities.java:34:in `get_proxy_class'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/site_ruby/shared/builtin/javasupport/java.rb:45:in `const_missing'
        from (irb):42:in `evaluate'
        from org/jruby/RubyKernel.java:1087:in `eval'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:158:in `eval_input'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:271:in `signal_status'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:270:in `signal_status'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:155:in `eval_input'
        from org/jruby/RubyKernel.java:1417:in `loop'
        from org/jruby/RubyKernel.java:1190:in `catch'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:154:in `eval_input'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:71:in `start'
        from org/jruby/RubyKernel.java:1190:in `catch'
        from /usr/local/rvm/rubies/jruby-1.6.0/lib/ruby/1.8/irb.rb:70:in `start'
        from /usr/local/rvm/rubies/jruby-1.6.0/bin/irb:17:in `(root)'

看起来它没有将驼峰命名法解析为适当的 Java 包名称。我究竟做错了什么？我相信我已经正确设置了类路径（最后 3 个条目），尽管 xerces 可能会被包含两次，但可能会存在一些冲突：

$ echo $CLASSPATH
:/jellly/Maui1.2:/jellly/Maui1.2/src:/jellly/Maui1.2/bin:/jellly/Maui1.2/lib/commons-io-1.4.jar:/jellly/Maui1.2/lib/commons-logging.jar:/jellly/Maui1.2/lib/icu4j_3_4.jar:/jellly/Maui1.2/lib/iri.jar:/jellly/Maui1.2/lib/jena.jar:/jellly/Maui1.2/lib/maxent-2.4.0.jar:/jellly/Maui1.2/lib/mysql-connector-java-3.1.13-bin.jar:/jellly/Maui1.2/lib/opennlp-tools-1.3.0.jar:/jellly/Maui1.2/lib/snowball.jar:/jellly/Maui1.2/lib/trove.jar:/jellly/Maui1.2/lib/weka.jar:/jellly/Maui1.2/lib/wikipediaminer1.1.jar:/jellly/Maui1.2/lib/xercesImpl.jar:/jellly/boilerpipe-1.1.0/boilerpipe-1.1.0.jar:/jellly/boilerpipe-1.1.0/lib/nekohtml-1.9.13.jar:/jellly/boilerpipe-1.1.0/lib/xerces-2.9.1.jar

我建议不要尝试猜测我们放在 Java:: 下的模块名称，因为对于不寻常的包，它可能会被严重破坏。使用 java_import 'your.weird.package.ArticleExtractor' 或者如果所有包组件都与 Ruby 方法命名兼容，您也可以执行 Java::your.weird.package.ArticleExtractor。

另外，由于您可能会遇到这种情况...您需要将 INSTANCE 变量引用为 ArticleExtractor::INSTANCE，因为我们将其映射为 Ruby 常量。

玩得开心！