thejavajar

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.