Gem wrapper for Apache Jena

This Gem provides convenience access to the Apache Jena RDF platform. Jena is a widely used Java platform for parsing, storing, manipulating, querying and publishing semantic web data and linked data. This gem provides a single dependency so that JRuby programs can access all of the capabilities of Jena, including TDB, conveniently from JRuby.

This gem provides the following benefits:

a single dependency which includes all of the .jar files for the latest release of Jena (currently 2.7.0) and TDB (currently 0.9.0)
import of some of the key classes used by Jena-based programs into a Jena:: module, to make code more compact
some additional utility and convenience methods

Using the gem

Once installed, just add to your code:

require 'jena_jruby'

or add a suitable dependency to your bundle spec.

Access to Jena from Java

Create a model:

m = Jena::Core::ModelFactory.create_default_model

(note that JRuby automagically converts Java CamelCase names to Ruby lower_case names)

Add a statement:

jruby-1.6.5 :003 > m = Jena::Core::ModelFactory.create_default_model
 => #<Java::ComHpHplJenaRdfModelImpl::ModelCom:0x135a4815>
jruby-1.6.5 :004 > s = Jena::Core::ResourceFactory.create_resource "http://example.org/s"
 => #<Java::ComHpHplJenaRdfModelImpl::ResourceImpl:0x7b0f62cb>
jruby-1.6.5 :005 > o = Jena::Core::ResourceFactory.create_resource "http://example.org/o"
 => #<Java::ComHpHplJenaRdfModelImpl::ResourceImpl:0x4879c985>
jruby-1.6.5 :006 > p = Jena::Core::ResourceFactory.createProperty "http://example.org/p"
 => #<Java::ComHpHplJenaRdfModelImpl::PropertyImpl:0x3f7cd159>
jruby-1.6.5 :007 > m.add s,p,o
 => #<Java::ComHpHplJenaRdfModelImpl::ModelCom:0x135a4815>
jruby-1.6.5 :009 > m.toString
 => "<ModelCom   {http://example.org/s @http://example.org/p http://example.org/o} | >"

Building and installing the gem

Since jena-jruby now includes TDB, the easiest way to get the full set of jars necessary to support Jena is to use Maven to list the dependencies declared in the TDB pom.xml. For convenience, this is packaged in a bash script:

ian@rowan-15 $ export JENA_TDB_ROOT=~/whereever/you/have/the/tdb/source
# note: defaults to ~/workspace/apache-jena-tdb

ian@rowan-15 $ cd ~/workspace/jena-jruby/
ian@rowan-15 $ bin/update_jars_maven
Changing to TDB directory /home/ian/workspace/apache-jena-tdb
~/workspace/apache-jena-tdb ~/workspace/jena-jruby
Cleaning old versions and recompiling ...
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building TDB
[INFO]    task-segment: [clean, install]
[INFO] ------------------------------------------------------------------------
  .. lots of maven output ..
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 17 seconds
[INFO] Finished at: Thu Jan 05 00:18:09 GMT 2012
[INFO] Final Memory: 68M/718M
[INFO] ------------------------------------------------------------------------
Collecting dependencies ...
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'dependency'.
[INFO] ------------------------------------------------------------------------
[INFO] Building TDB
[INFO]    task-segment: [dependency:copy-dependencies]
[INFO] ------------------------------------------------------------------------
[INFO] [dependency:copy-dependencies {execution: default-cli}]
[INFO] Copying icu4j-3.4.4.jar to /home/ian/workspace/apache-jena-tdb/target/dependency/icu4j-3.4.4.jar
  .. more maven output ..
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2 seconds
[INFO] Finished at: Thu Jan 05 00:18:12 GMT 2012
[INFO] Final Memory: 35M/349M
[INFO] ------------------------------------------------------------------------
~/workspace/jena-jruby
Changing directory back to /home/ian/workspace/jena-jruby
Copying deps to ./javalib
Creating log4j config

ian@rowan-15 $ rake build
rake/rdoctask is deprecated.  Use rdoc/task instead (in RDoc 2.4.2+)
jena-jruby 0.3.0 built to pkg/jena-jruby-0.3.0-java.gem