RORLAMP Development

Amazon Simple Queue Service (Amazon SQS) is a distributed queue messaging service. The idea of SQS is to remove the direct associations between producer and consumer and act as mediator between them.

e.g

Consider that you have a large  application like websites monitoring which involve many stages like

• Downloading a website
• Processing the downloaded website
• Generating report of the above processing

So instead of clubbing the above three one can just split them on their specific need(based on the work they do)  with each doing their respective task and on completion notify the other about it completion.

The traditional approach (called as Client-Server architecture) is to send the notification using a simple HTTP , REST , SOAP etc request. But it too has some disadvantage as it require extra care and  precision  to handle all possible response e.g Time-out,Server down etc.

One can save this time and effort my using SQS.

e.g Instead of sending the direct request to Server one can use to SQS to interact with Server/Client an can eventually cut down some of drawback of traditional architecture.

Setting up Amazon SQS in Ruby: There are various library available for using Amazon SQS in Ruby (e.g right_aws, sqs)

Pre-requitise:

• aws-access-key-id
• aws-secret-access-key
• ruby-library(right_aws or sqs gem)
  both of which is provide by the Amazon (or you can ask for incase) during the process of account-registration

In your irb console

require "rubygems"

require "right_aws"

aws_access_key_id  = "Your access key id"

aws_secret_access_key = "Your secret access Key"

sqs = RightAws::SqsGen2.new(aws_access_key_id,aws_secret_access_key)

This basically initialize the sqs object for you to work on.

One can create a new queue just by a single method.

 queue(queue_name, create=true, visibility=nil) 

carefully look at parameter supplied.

queue_name => name of  queue.

create => true (create a queue if it does not exist (optional)).

visibility => set visibility (which make the message reappear after a specified time if not  delete from queue).

One key point about visibility is that one can’t set visibility more than 7200 sec for a  queue or a message .But you can set so from RightScale (Cloud Computing management Platform).

e.g

my_queue = queue('queue_1')

just look at few other methods.

1. send_message or push :- Send message to the specified queue.

 my_queue.send_message "This is my first message"

2. receive or pop :- Receive message from the specified queue.

 message_received = my_queue.receive

puts message_received.body
=> "This is my first message"

2.1 receive_messages : – There is also a method called receive_messages to receive an  array of messages but it never returned me more than one message so if it work for you  it fine then syntax is like this

 receive_messages(number_of_message=1,visibility=nil)

 my_queue.receive_messages(2,60) => return and array of messages

3. delete : –  Delete a  message or a queue

 my_queue.delete => "delete the my_queue for SQS"

 message_received.delete => "delete the message from the intended queue"

4. size :- Specify the no of message in the queue

 my_queue.size => 4 ("4" message in my_queue)

5. name :- Specify name of the queue

 my_queue.name => "queue_1" (Name of the queue)

Note : – There is delay lag in all request and response sent/received to/from  SQS server don’t assume to work it instantaneous approximately of around 45 sec -1 minute(can be more)

e.g

If you send  a message to the queue don’t assume it to appear instantaneously in the queue

Pricing Model => $0.10 per 100,000 requests.

Message Size => 64 KB

For more information on Pricing and message size click  here.

Thank you

In many application we want to convert one office format to another office format e.g doc to PDF , doc to html etc.We can import/export document using OpenOffice easily,but this is manual way.But standalone/Web based application we have to automate this functionality. JODConverter,the Java OpenDocument Converter, It converts documents between different office formats using OpenOffice.

JODConverter supports all conversion which is given by OpenOffice.More Info regarding format you can visit here.

Now,JODConverter is a java library so it can be used using java application,or using command line,or by making web service so any other language(RUBY,.NET,PHP,PYTHON) can used this conversion directly.
Convert Office is a ruby Wrapper of jodconverter .Which is used to convert office format to another office format.
Continue reading »

In previous article we have seen that how to start nailgun server,and use of nailgun in shortly.

Now in this article how to use nailgun using ruby application which directly/indirectly use java library or java application. You can start with nailgun manually as shown previous article and configure ng as per need.Or you can install nailgun plugin from github.
Continue reading »

Lately there have been too many people wanting to know how to execute Javascript in Celerity.
Let me show you how it done.
First a quick note on JRuby installation.
Here are few useful links to install JRuby under

1. Linux(ubuntu) should work for other linux packages as well.
2. Windows.

Just to confirm,kindly type jruby -v on terminal or cmd depending on OS you are using and you should get the version of jruby you are running.

Mine output was

jruby -v
jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2010-03-11 6586) (OpenJDK Client VM 1.6.0_0) [i386-java]

Now go ahead and just install celerity gem.
More about celerity installation can be found here also just quickly check whether the sample code work for you.If it work then your ready go and for those it don’t well you just need to tweak a bit.

Ok enough of installation,now we start with running javascript under celerity.
Here is my test HTML File “index.html.”

 <html>

  <head>

    <script type=”text/javascript”>

      function populateDropDown() {

        var select = document.getElementById(’colors’);

        var options = ['Ruby', 'JRuby', 'IronRuby', 'Rails'];

        var index;

        for(index = 0; index < options.length; index++) {

          var option = document.createElement(’option’);

          option.appendChild(document.createTextNode(options[index]));

          option.value = options[index];

          select.appendChild(option);

        }

     }

  </script>

  <script type=”text/javascript”>

    function add_new_language() {

      var wrapper = document.getElementById(’wrapper’);

      var input = document.createElement(’input’);

      var br = document.createElement(’br’);

      input.setAttribute(’type’,'text’);

      wrapper.appendChild(br);

      wrapper.appendChild(input);

    }

  </script>

 </head>

 <body onload=”populateDropDown()”>

  <h1>Select Your Favourite Language</h1>

  <form>

    <select id=”colors”>

    </select>   <a href=”#” onclick=”add_new_language()” >More Language</a>

    <br/>

    <span id=”wrapper”>

    </span>

  </form>

 </body>

</html>

Here my sample code in JRuby.

 require "rubygems"
 require "celerity"

 browser = Celerity::Browser.new(:browser => :firefox)
 browser.goto("file:///home/guest/Desktop/index.html")

Now basically one can run the javascript just by a simply calling the method fire_event on the html tag that has the associated event that you want to fire.
 e.g the anchor tag above has a onclick event associated with it.

browser.document.get_html_elements_by_tag_name('a').first.fire_event('click')
 

Now modified the html content i.e (after javascript execution) can be obtain using “browser.xml”.

Here mine output.

  puts browser.xml

<?xml version=”1.0″ encoding=”ISO-8859-1″?>

<html>
 <head>
  <script type=”text/javascript”>
   //<![CDATA[
     function populateDropDown() {
       var select =        document.getElementById('colors');
       var options = ['Ruby', 'JRuby', 'IronRuby', 'Rails'];
       var index;
       for(index = 0; index < options.length; index++) {
         var option = document.createElement(’option’);
         option.appendChild(document.createTextNode(options[index]));
         option.value = options[index];
         select.appendChild(option);
       }
     }
  //]]>
  </script>

  <script type=”text/javascript”>
   //<![CDATA[
     function add_new_language() {
       var wrapper =document.getElementById('wrapper');
       var input = document.createElement('input');
       var br = document.createElement('br');
       input.setAttribute('type','text');
       wrapper.appendChild(br);
       wrapper.appendChild(input);
     }
   //]]>
  </script>
 </head>

 <body onload=”populateDropDown()”>
  <h1>Select Your Favourite Language</h1>

    <form>
      <select id=”colors”>
        <option value=”Ruby” selected=”selected”>Ruby</option>
        <option value=”JRuby”>JRuby</option>
        <option value=”IronRuby”>IronRuby</option>
        <option value=”Rails”>Rails</option>
      </select>

      <a href=”#” onclick=”add_new_language()” >More Language</a>
      <br/>
      <span id=”wrapper”>
        <br/>
        <input type=”text”/> <!— generated by javascipt –>
      </span>
    </form>
 </body>
</html>

Here how I made the whole flow generic.

#List of Tag that has event Handler
TAGS   =  ['iframe' ,'img', 'frame', 'frameset', 'ilayer', 'input', 'layer', 'select', 'a', 'area', 'form', 'object', 'script', 'embed', 'applet', 'option', 'button']

# defining a Constant with list of event_hander
EVENT_HANDLERS  = ['onclick','onmouseover','onselect','onsubmit']

# List of events that can trigger a function
EVENTS    = ['click','mouseover','select','submit']

 TAGS.each do |tag|
    browser.document.get_html_elements_by_tag_name(tag).each do |element|
       EVENT_HANDLERS.each_with_index do |event_handle,i|
          element.fire_event(EVENTS[i]) if element.hasAttribute(event_handle)
       end
    end
 end

Note : – One didn’t need to fire_event for onload as the onload event is fired as soon as the page is load using browser.goto .

Other options available are : –

Johnson in Ruby
Watir in Ruby
Selenium in JRuby

Thank You

In previous article we have seen that how pdf is generated  using act_as_flying_saucer plugin.

Following code snippets is used for generating pdf with bookmark .

<html>
  <head>

    <bookmarks>
      <bookmark <strong>name="Section 1" href="#section_1"</strong>>
        <bookmark name="Section 1.1" href="#section_11"></bookmark>
        <bookmark name="Section 1.2" href="#section_12"></bookmark>
      </bookmark>
      <bookmark name="Section 2" href="#section_2"></bookmark>
      <bookmark name="Section 2" href="#section_3"></bookmark>
    </bookmarks>

  </head>

  <body>

    <div style="page-break-before: always;">
      <a <strong>name="section_1"</strong>>Section 1</a>
    </div>
    <div style="page-break-before: always;">
      <a name="section_11">Section 1.1</a>
    </div>
    <div style="page-break-before: always;">
      <a name="section_12">Section 1.1.2</a>
    </div>
    <div style="page-break-before: always;">
       <a name="section_2">Section 2</a>
    </div>
    <div style="page-break-before: always;">
       <a name="section_3">Section 3</a>
    </div>

  </body>

</html>

<bookmark name=”section 1″  href=”#section_1″> tag is used to generate bookmark.
which contains name attribute for displaying name of bookmark.
href attribute is used for navigation purpose.

<bookmark> tag can be nested so it can be used for generating nested bookmark
<bookmark> tag is wrapper with <bookmarks> tag. This tag placed in html header.

Now in html body whichever anchor tag has name attribute with value as same as bookmark
href value on that position user is navigated.

Mainly two tag is used which is displayed below.

<bookmarks>
<bookmark name=”Name Of Bookmark”  href=”#bookmark1“>< /bookmark>
</bookmarks>
<a name=”bookmark1″>Text</a>

Pdf with password protected in rails

In previous article we have seen that how pdf is generated  using act_as_flying_saucer plugin. Now  act_flying_saucer  has added support for  password protected pdf.

To generate PDF with password protection just pass :password=>”xxx” to render_pdf method.

render_pdf :file=>'pdf/generate_pdf.html.erb',:password=>"xxx"</pre>

You can install act_as_flying_saucer plugin

 script/plugin install git@github.com:amardaxini/acts_as_flying_saucer.git

For  further details you can visit article or visit http://github.com/amardaxini/act_as_flying_saucer

In this article i have just taken a short example describing vertical table,and its implementation using rails.

When table has no fixed column it has dynamic fields .data is not stored on separate column but data stores in vertical fashion.

For implementing vertical table table has mainly 2 columns key and value pair.key is like database column name and value contains actual data.

Lets take an e.g

Consider website in which it contains various products and its comparison ,searching and many more features.product can be mobile,car etc.Product has many items.item may be nokia 6600,nokia n72 etc.

Here our aim is not compare aur search items.Here our main aim is how vertical table concept is applied.Suppose we have to build only single product comparison site then each product has it’s own attributes that can be easily build with adding column for each product.

we are developing generic site(multiple product).so there is no fixed attributes,each product has it’s own attributes either we create different model for each product or we can proceed with vertical table concept.

• Product has many Product Attributes.
• Product has many Items.
• Item has many Item Attributes.
• Item Attribute belongs to Product Attribute.

Product Attribute mainly requires 3 fields

name : which is used for key in vertical table(i.e column name)

option_type : which is used for viewing different form of data when item is created .(textbox,dropdown,checkbox,multi option)

option : which contain option if its drop down or multi option(serialize)

Item has only name field which is optional.

Item attribute mainly required 3 fields

name : key name or column name

value : actual value

item_id : foreign key of item

It is used where table has dynamic fields,and it only concern with data.

Here data grows vertically.

It has mainly key ,value pair.

Source code of above example is hosted on github http://github.com/amardaxini/vertical_table_demo

For More info about vertical table you can visit http://weblogs.foxite.com/andykramek/archive/2009/05/03/8369.aspx

Static site using rails

As we know rails is mainly used for dynamic website.we can also display static web pages or we can deploy full static website using rails. The following code can help us to display static pages.

Step 1:-Create Rails project

rails static_site

Step 2:-Generate StaticPage Controller

ruby script/generate controller static_pages page

Step 3:- Create StaticPage Class in Model

 class StaticPage
   Formats = {
       "html" => "text/html",
       "png" => "image/png",
       "jpg" => "image/jpg"
     }
 end

Step 4:- Add following line in routes.rb

map.page "page/:filename.:format", :controller => 'static_pages', :action => 'page'

Here we are passing filename as parameter which is static file name.

This will generate url as http://sitename/page/static_filename.html

Step 5:- Now add following line into static_pages controller

def page
 send_file
 "#{Rails.root}/app/views/static_pages/#{params[:filename]}.#{params[:format]}",:disposition =>'inline',:type => StaticPage::Formats[params[:format]]
 end

Step 6:- All the static pages place in RAILS_ROOT/app/views/static_pages/ folder

Step 7 :- Start server and Type url as shown below.

ruby script/server

Url may be

http://railstech.com/page/contactus.html or
http://railstech.com/page/faq.html
Or In Development Mode
http://localhost:3000/page/faq.htm
http://localhost:3000/page/contactus.html

Today, I have started testing Beta release of Rails 3.0.By Default Rails 3.0 start with webrick.To start with mongrel do following steps.

1)Install mongrel gem

sudo gem install mongrel

2) After installing mongrel gem go to config/boot.rb file

and add following line

  require "mongrel"

3) Start server as rails server

Rails Pdf Plugin act_as_flying_saucer

There are various ways to generate pdf documents in any language.In Rails we can use prawn library ,HtmlDoc,PrinceXml and many other library,using their api we can generate pdf document.Basically the primary goal is converting HTML web pages to PDF Document,without much changing existing CSS and HTML.

Using the Flying Saucer Project we can achieve this.we can convert HTML + CSS to PDF documents without much changing HTML and CSS. It also support CSS 2 and many properties of CSS 3 for printing Header,Footer,Page Number,Paginated Tables and many more.This Project is built on Java so Java is required on system.

Lets Start How to generate PDF Using Flying Saucer.

 script/plugin install git://github.com/amardaxini/acts_as_flying_saucer.git

This Plugin forked From

http://github.com/dagi3d/acts_as_flying_saucer

Which has older version of flying saucer project.

Next Step after installing plugin add flying_saucer.rb file at config/initializers.

ActsAsFlyingSaucer::Config.options = {
:java_bin => "/usr/bin/java",          # java binary
:classpath_separator => ':',  # classpath separator. unixes system use ':' and windows ';'
:tmp_path => "/tmp",          # path where temporary files will be stored
}

After Setting Java path , classpath separator and tmp path now do following step.

class PdfController < ActionController::Base
  acts_as_flying_saucer

  def generate_pdf
    render_pdf :template => 'pdf/pdf_template'
  end
end
  render_pdf :file=>'pdf/generate_pdf.html.erb'
  render_pdf :template=>'pdf/generate_pdf.pdf.erb',
             :send_file => { :filename => 'pdfdoc.pdf' }

Add act_as_flying_saucer to controller then render_pdf.There are various ways to render pdf using “template” or “file“,:send_file option use to send pdf file to client side.if we are using any external css file then this css shoulda have media option as ‘print’.

<%= stylesheet_link_tag 'pdf' ,:media=>'print' %>

If pdf containing images which generate on the fly.so instad of using

<%= image_tag %>

use

 <img src=" " >

Before rendering PDF validate HTML,like whether all tags are close properly or not.otherwise it gives an parse error.

Now You are ready to Generate PDF. Hurray!!!!!!!!!

How to generate Header, Footer,Page Number and Automation Of HTML Validation will be discussed in next post.