thejavajar

Data distribution is a pretty cool topic. Recently, I have been working with Hazelcast, which is an open source clustering and data distribution platform for Java. Well, I really like what I have seen so far and I figured why not have some fun with Hazelcast and Groovy.

I started by adding the Hazelcast 1.7.1 jar to $GROOVY_HOME/lib. Hazelcast, at an introductory level, provides distributed implementations of java.util { Queue, List, Set, Map }. I can run a Groovy script on multiple JVM’s and I can share a Map of customers on each instance. For example:

def customersMap = Hazelcast.getMap("customers")

Now, I have an instance of Map and I can add values using Hazelcast’s distributed id generator:

def idGen = Hazelcast.getIdGenerator("customer-ids")
def id = idGen.newId()
customersMap.put(id, "Customer $id")

So, that was pretty simple, right? Here is the entire Groovy script HazelcastGroovynessAdd.groovy:

import com.hazelcast.core.Hazelcast
import com.hazelcast.core.IdGenerator

def customersMap = Hazelcast.getMap("customers")
def idGen = Hazelcast.getIdGenerator("customer-ids")
def id = idGen.newId()
customersMap.put(id, "Customer $id")

I can open up a few different command prompts and enter:

> groovy HazelcastGroovynessAdd.groovy

Now, the customers Map has a few customers in it and our Groovy scripts are still running. Let’s add an com.hazelcast.core.EntryListener to the customers Map so we can detect a com.hazelcast.core.EntryEvent. Here is HazelcastGroovyness.groovy:

import com.hazelcast.core.Hazelcast
import com.hazelcast.core.EntryListener
import com.hazelcast.core.EntryEvent

def listener = [
	entryAdded: { EntryEvent ev ->
		println "key $ev.key was added with value $ev.value to $ev.name"
		Hazelcast.getMap("customers").values().each {
			println it
		}
	},
	entryUpdated: { EntryEvent ev -> },
	entryRemoved: { EntryEvent ev -> },
	entryEvicted: { EntryEvent ev -> }
] as EntryListener

def customersMap = Hazelcast.getMap("customers")
customersMap.addEntryListener(listener, true)

In the above code, we define listener which implements com.hazelcast.core.EntryListener. I now start up HazelcastGroovyness.groovy at a new command prompt(s):

> groovy HazelcastGroovyness.groovy

We can go back to our original HazelcastGroovynessAdd.groovy script and open (re-open) a few more command prompts and run the script that adds customers to the Map. Now in each running instance of HazelcastGroovyness.groovy we see something like:

key 2000001 was added with value Customer 2000001 to c:customers
Customer 2000001
Customer 1000001
Customer 1

Hazelcast is very cool, easy to use technology that provides distributed data with a few lines of code, especially with Groovy. More information can be found at Hazelcast’s website and at the project site at Google Code.

Grails is changing the way Java developers approach Web development. If you are not familiar with Grails, it is a Web application platform for the agile and dynamic language, Groovy, that runs on the Java Virtual Machine. There are plenty of available books on Groovy and Grails and there is a plethora of blog posts and online documentation to help you get started with your first Groovy and Grails project. This article will discuss creating a simple Grails application for JBoss AS 5.1.0 GA and demonstrate how simple Java Web development can be.

I have taken some time to explore developing a simple Grails 1.2-M3 application and deploying it on JBoss AS 5.1.0GA. Grails is all about productivity. In a few short steps, I create a simple Web application, generate a Web archive (.war) file and deploy it on JBoss AS 5.1.0 GA.

After Grails 1.2-M3 is installed and properly setup, I open a command prompt and enter

> grails create-app

and when I am prompted, I enter a name for my application.

> demo

A directory is created with the same name as my application. I then navigate to that directory.

> cd demo

Next, I create two domain classes to represent the solution to my business problem, storing company information in a database.

> grails create-domain-class org.axiomaticit.model.Company
> grails create-domain-class org.axiomaticit.model.Address

The above commands create two .groovy files in the directory grails-app/domain/org/axiomaticit/model/, Company and Address. Here is what the Company.groovy file looks like:

package org.axiomaticit.model

class Company {
    static constraints = {

    }
}

Next I open the Company.groovy and Address.groovy files in a text editor or IDE and add some detail. Here is the Company.groovy file after I add some fields and constraints:

package org.axiomaticit.model

class Company {

    String name
    String website

    static hasOne = [address:Address]

    static constraints = {
        name(blank:false)
        website(blank:false, url:true)
        address(nullable:true)
    }

    String toString() {
        "$name"
    }
}

And here is the Address.groovy file:

package org.axiomaticit.model

class Address {

    Company company
    String street1
    String street2
    String city
    String state
    String postalCode

    static constraints = {
        company(nullable:false)
        street1(blank:false)
        street2(blank:true)
        city(blank:false)
        state(blank:false)
        postalCode(blank:false)
    }

    String toString() {
        "$street1 $city, $state"
    }
}

If you are not familiar with Groovy and the conventions of Grails, this might be a little weird to look at. If you are a Java developer, some of the above code looks a lot like what you already know, right? Let’s talk about what I just did. I created two classes to represent company information. First, I created a company class with a few important fields like ‘name’ and ‘website’.

    String name
    String website

Then I created another class, Address, to represent standard US address data.

    String street1
    String street2
    String city
    String state
    String postalCode

I also added an Address to the Company class,

static hasOne = [address:Address]

and a Company to the Address class.

Company company

Don’t get too wrapped up in all the details if you are new to Grails, but what you should understand is that I am building a domain model and creating properties and relationships between persistent entities. The Grails documentation is quite detailed and the user community is also very helpful if you get stuck with the Grails conventions and semantics of Groovy.

Now that I have my domain model, I want to create the controllers and views for my Web application. Controllers and views? Think MVC (Model, View, Controller). So, I go back to my command prompt and enter each command:

> grails generate-all org.axiomaticit.model.Company

> grails generate-all org.axiomaticit.model.Address

The commands above will create a few things based the domain model objects; they create default controllers and views that will support basic CRUD (Create, Read, Update, Delete) functionality. The controllers will be in grails-app/controllers/org/axiomaticit/model/ and the views will exist in grails-app/views/company and grails-app/views/address respectively for each domain model object Company and Address. Let’s go ahead and see what I have created and run the application from the command line.

> grails run-app

Once the application starts up, I browse to http://127.0.0.1:8080/demo and test out the application. It might not be everything I wanted, but I have a great starting point, right? Let’s deploy this on JBoss AS 5.1.0 GA. Back to the command line to create a Web archive (.war) file.

> grails war

If everything builds properly, I have just created a file, demo-0.1.war, that I can drop into the JBoss deploy directory. I can start up JBoss and point the browser at http://127.0.0.1/demo-0.1 and test out the application. Wow, that took about 10-20 minutes and now I have a fully-functional Web application. Grails is a great platform for proof-of-concept work but because it is based on proven technologies like Spring and Hibernate, many developers are moving Grails applications right into production. Combine Grails with an enterprise level application server like JBoss AS 5.1.0 and you have productivity built on top of dependability.

This is a copy of what I posted at Jboss.org.

I am fairly new to Ruby but I do have experience with Groovy so I have found learning and experimenting with Ruby somewhat of an easy effort. The Ruby community is pretty big so there are plenty of blog posts and other Web sites that are available, via a Google search, to help understand some problems when I get stuck. I started playing around with Ruby Proc (procedures), if/elsif/else and case/switch statements and here is what I am having fun with:

# define our apple Proc
apple = proc { |t| puts "my apple" + t }

Above we have our executable (proc) code assigned to the ‘apple’ variable.

# doIt1 with if statements
def doIt1(c, t)
  if t.respond_to?("call")
	puts "-- callable"
    c.call " is awesome"
	t.call " is really awesome"
  elsif t.kind_of?(Array)
	puts "-- not callable Array"
	t.each { |t1| c.call t1 }
  else
	puts "-- not callable String"
	c.call t
  end
end

Then we have a method ‘doIt1(c,t)’. This method expects 2 arguments; the first argument, ‘c’, I expect is a Proc and the second argument, ‘t’, I expect to be a Proc, Array or String.

if t.respond_to?("call")

The ‘if’ statement checks to see if ‘t’ has a method named ‘call’ that it will respond to. I think the ‘respond_to’ method is great for dynamic languages. I could have just checked to see if ‘t’ is a Proc as well, but then that limits me to one Object type, right?

t.kind_of?(Array)

The ‘elsif’ statement checks to see if ‘t’ is of type Array. Like instanceof in Java.

# doIt2 with case/switch block
def doIt2(c, t)
	case t
	  when Proc
	    puts "-- callable"
		c.call " is awesome"
		t.call " is really awesome"
	  when Array
	    puts "-- not callable Array"
		t.each { |t1| c.call t1 }
	  when String
	    puts "-- not callable String"
		c.call t
	  else
	    puts "not valid"
	end
end

Then I created a method just like ‘doIt1′ called ‘doIt2′. In ‘doIt2′, I used a case/switch statement and handled things similarly to ‘doIt1′. In the second method, I check ‘t’ to be of type String and have a default case for when ‘t’ is not a Proc, Array or String.

# doIt1 tests
doIt1 apple, apple
doIt1 apple, " works good"
doIt1 apple, " works hard"
doIt1 apple, [" looks good", " looks elagant", " looks shiny"]

# *'s used to separate method tests
puts "*" * 40
puts "*" * 40

# doIt2 tests
doIt2 apple, apple
doIt2 apple, " works good"
doIt2 apple, " works hard"
doIt2 apple, [" looks good", " looks elagant", " looks shiny"]

Then I wrote a few ‘tests’ to see what would happen. Ruby is fun and I definitely enjoy working with Ruby and Groovy. Here is the full script file: appleProc.rb

Ruby on Rails is something that I have been meaning to look into for a while. I have been working with Java for most of my professional IT career and I work with Groovy on Grails whenever I have it my way. I even work with PHP and Python when working with some clients or when I feel like doing something different. So, I owed it to myself to give Ruby on Rails a good look. Why? Because there are a lot of people who are passionate about RoR and Rails is what inspired Grails after all.

I have been working with a pretty simple Web application that requires simple security, data access and minimal navigation. I will post more about the application once I have it done, but I can see why people are passionate about RoR just like I am passionate about GoG. Ruby is elegant, no doubt about it and Rails fits in to bring it all together for Web developers who want to focus on solving the problem at hand rather than fighting the technology stack. I am enjoying my experience with RoR thus far and would recommend that other Web developers who have not yet tinkered with Ruby on Rails give it a try for a few hours a night for a couple of days. Check http://rubyonrails.org/ out. There is a plenty of documentation and links to get you started.