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PDF::Writer and Ruby on Rails 2.1

Some days ago, Ruby On Rails 2.1 saw the light of day and as usual, i eagerly updated my Daily Fratze project.

I had some minor problems due to an old version of will_paginate and some major ones with my use of PDF::Writer.

The PDF::Writer library still works very well but the the instructions here (under PDF::Writer (Austin Ziegler) on how the register an “rpdf” template handler don’t apply anymore due to changes in the Rails template system but can easily be fixed:

In environment.rb change

ActionView::Base.register_template_handler 'rpdf', ActionView::PDFRender

to

ActionView::Template.register_template_handler 'rpdf', ActionView::PDFRender

And also change your ActionView::PDFRender class to:

module ActionView # :nodoc:
  require 'pdf/writer'
  class PDFRender
    PAPER = 'A4'
    include ApplicationHelper
    include ActionView::Helpers::AssetTagHelper
    include ActionView::Helpers::TextHelper      
    include ActionView::Helpers::TagHelper
    include ActionView::Helpers::UrlHelper
 
    def initialize(action_view)
      @action_view = action_view
    end
 
    # Render the PDF
    def render(template, local_assigns = {})
      @action_view.controller.headers["Content-Type"] ||= 'application/pdf'
 
      # Retrieve controller variables
      @action_view.controller.instance_variables.each do |v|
        instance_variable_set(v, @action_view.controller.instance_variable_get(v))
      end
 
      pdf = ::PDF::Writer.new( :paper => PAPER )
      pdf.compressed = true if RAILS_ENV != 'development'
      eval template.source, nil, "#{@action_view.base_path}/#{@action_view.first_render}.#{@action_view.finder.pick_template_extension(@action_view.first_render)}" 
 
      pdf.render
    end
 
    def self.compilable?
      false
    end
 
    def compilable?
      self.class.compilable?
    end
  end
end

And enjoy happy PDF generation 😉

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Hibernate and Inheritance Mapping

Hibernate supports multiple types of inheritance mapping, some of them (Table per class, Table per subclass) using a discriminator column to decide the class.

The type of the discriminator can be one of

string, character, integer, byte, short, boolean, yes_no, true_false

In case you need to use any other than string or character, i.e. integer, you have to give the base class a default discriminator-value like 0 or -1 or whatever fits, otherwise you’ll end up with a an exception like:

org.hibernate.MappingException: Could not format discriminator value to SQL string

as Hibernate uses the class name of the base class to derive a default value.

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Division by zero

Just a quick reminder for myself:

int a = 0/0; // Throws ArithmeticException
double d1 = 0/0.0; // d1 is NaN
double d2 = 1/0.0; // d2 is Infinity
double d3 = -1/0.0; // d3 is -Infinity

Can cause some headache if things fall apart in the JDBC driver and not before. Grmpf.

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Ampersands and XHTML

A regular expression to replace all ampersands (&) in a text that are not part of an entity:

t = t.gsub(/&(?!#?\w+;)/, '&')

Language is ruby. The regexp feature used is called a negative lookahead.

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SCJP, finally!

More than a year ago i decided to do the Sun Certified Java Programmer. Shortly after i bought this book, the projects at work and at home were somewhat overwhelming and after all, i realized that a big part of the SCJP is about some weird, crazy and sometimes wrong design decisions of the Java language. Some of them i mentioned under this tag.

Last month i realized i had some spare time, signed up at Prometric and had a 2nd look at the book and on my good Java experience from the last 6 years.

First thing: The “Java 5 Study Guide” isn’t a bad book but the “MasterExam” software on the enclosed cd is a master piece of crap. Not only the gui is as shitty as it gets but some of the answers are just plain wrong.

Second thing: I bought the preparation kit from Whizlabs for 50€. This thing isn’t bad at all and helps you get prepared for the craziness thrown at you.

Third: Being good at something is always great 😀 It rocks, really. Like single trail riding or music with electric guitars while driving open. It’s like drugs but not that unhealthy.

After about 2 weeks of preparing, I arrived 30 minutes early at “New Horizons” in Cologne, took the test certainly in english as i prepared with english material and finished somewhat 50 minutes later (you have officially around 3 hours to take the test). The nice proctor asked me if i wanted to use the toilet as she saw my report being printed: 90%, pass! Wooot!

I thought about this post at Jans. I really like the guy who wins a million dollars at Who wants to be a Millionaire and has the guts to call his dad but not ask for help and instead tells him he is going to win a million dollars. I can totally relate to that as i always had fun taking test and scoring at the upper limit 😀

So today i’m gonna eat an extra portion of Cookies & Cream and leave you with the following piece of Java madness:

Read the complete article »

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