How can somebody be so stupid to choose “screen” as product name?
I mean the word “screen” has already a meaning! A very strong meaning! That means it is very difficult to google for the product “screen”. So you have to add more keywords into your search. It is a nightmare!
If you get this Error Message:
ActionView::Template::Error (blueprint/ie.css isn't precompiled)
Than that means that your ie.css isn’t precompiled 
No. Seriously. If you get this message, probably you are running on production and your css files are not precompiled. Take a deeper look to the Assets Pipeline in Rails 3.1.X. If your css and js files are in the right place, you can fix this error message by executing this command here:
rake assets:precompile
Or with JRuby:
jruby -S rake assets:precompile
That should generate all precompiled css and js files and fix the problem.
Trinidad is another HTTP Server for JRuby. I installed it with:
jruby -S gem install trinidad
I used before Mizuno. But I had some issues with Mizuno on my Linux Server. I still didn’t figured out why it was not running on Debian. Trinidad is right now running pretty good on Debian Linux. I will monitore it a while.
I have JRuby on Rails app, which is using an ueber JAR to access Neo4J. The Neo4J database is in the rails root directory unter “data/”. By starting the HTTP Server I got today this Exception:
IllegalArgumentException: No index provider 'lucene' found. Maybe the intended provider (or one more of its dependencies) aren't on the classpath or it failed to load.
The problem was in the “data/”. In some way it was corrupt. I am not sure. After I exchanged the “data/” directory with an older version, the HTTP Server started without any problems.
After I installed fresh unicorn I got this error message by starting “unicorn_rails”
Could not find activesupport-3.1.0 in any of the sources
I still don’t know what was exactly the problem. But after I closed the terminal and opened a new one, everything worked fine.
Unicorn is a pretty cool and super fast HTTP Server for Rack applications. You can install it with this command:
gem install unicorn
and you can run you Ruby on Rails app on it with this command:
<RAILS_ROOT>: unicorn_rails
Just navigate into your root app directory and type in “unicorn_rails”. By default it will run the server on Port 8080 and you app is available on:
http://localhost:8080
Unicorn is optimized for Linux/Unix machines! You can not run your JRuby app on it, because some native extensions are not yet implemented for JRuby.
This article show how to use ActiveRDF in Ruby on Rails to write queries for DBPedia. DBPedia is the semantic version of WikiPedia. Basically the whole knowledge in Wikipedia is available in DBPedia over RDF (Resource Definition Framework). There is a query language for RDF called SPARQL. With SPARQL and RDF you can write queries and fetch data from DBPedia/Wikipedia.
That is pretty awesome. You can see DBPedia/Wikipedia as a big Database or Knowledge base.
ActiveRDF is a Ruby GEM to use RDF in Ruby. To use it in Rails you have to add this two lines to your Gemfile
gem 'activerdf' gem 'activerdf_sparql'
In you application.rb file you have to add this line pretty much in the top.
require 'active_rdf'
In the same file, in the class part you have to configure the connection pool for RDF.
module TrophicWeb class Application < Rails::Application adapter = ConnectionPool.add_data_source(:type => :sparql, :results => :sparql_xml, :engine => :virtuoso, :url ="http://dbpedia.org/sparql") adapter.enabled = true Namespace.register(:dbpedia, "http://dbpedia.org/ontology/")
That’s it for the initialization. Now you can use it in your code. Here is an example how to fetch a species and the corresponding thumbnail uri.
species = RDFS::Resource.new("http://dbpedia.org/resource/Symphurus")
thumbnail = species.dbpedia::thumbnail.uri
Thats it.
Mizuno is Webserver for JRuby on Rails.
I looked for different options to run my JRuby App. After some googleing I found Mizumo. It was very easy to install:
jruby -S gem install mizuno
and very easy to start. Just go into the root directory of your rails app and exec.
mizuno
or if you want to start on Port 80.
sudo mizuno --port 80
Mizuno is the fastest option for Reck applications on JRuby:
Mizuno: 6106.66 req/s (mean) Jetty (via jruby-rack): 2011.67 req/s (mean) Mongrel: 1479.15 req/sec (mean)
Today I added activerdf to a rails project. I am running the project with jRuby. By starting the app I got this Error Message:
Could not find gem_plugin-0.2.3 in any of the sources
I could fix it by executing the following command:
jruby -S bundle install
That fixed the problem for me.
I am playing around with LinkedData, RDF and SPARQL. That are the basics of the semantic web, the web 3.0. ActiveRDF is a Ruby Framework for accessing LinkedData in a object oriented way. It is pretty cool. I installed the GEM on my MacBook Air:
gem install activerdf
And I installed the SPARQL Adapter:
gem install acitverdf_sparql
I started the ruby console to try the example from the front page of ActiveRDF. And I got this Exception:
ActiveRdfError: cannot execute query without data sources
The example from the ActiveRDF page does not work for me. I had to add one more line to make it work:
adapter.enabled = true
The full modified example is here:
require 'active_rdf'
adapter = ConnectionPool.add_data_source(:type => :sparql, :results => :sparql_xml, :engine => :virtuoso, :url => "http://dbpedia.org/sparql")
adapter.enabled = true
Namespace.register(:dbpedia, "http://dbpedia.org/ontology/")
tj = RDFS::Resource.new("http://dbpedia.org/resource/Thomas_Jefferson")
tj.dbpedia::birthPlace
tj.dbpedia::deathDate
query = Query.new.distinct(:o).where(tj, RDF::type, 
)
query.execute
This is working fine for me.
