Grails

Grails is an open source web application framework it is intended to be a high-productivity framework by following the “coding by convention” paradigm and ready-to-use development environment

Characteristics

• Web Framework
• Open Source
• Cross-platform
• MVC paradigm

Features

• Convention-over-Configuration
• Ready-to-use development environment
• Functionality available through mixins
• GSP technology
• Integrated ORM
• DRY (Don’t repeat yourself)
• Fullstack framework
• Scripting with Gant
• Tomcat application server embedded
• Transactional layout
• Plugin oriented
• Wide IDE Support
• Expressive Domain Specific Language
• Spring support
• Highly productive

Content

• Hello World
• Java Melody
• Grails and Bower Integration
• Download counter
• Externalized configuration
• Login functionality with Spring Security

Creating a simple structure in Grails

Creating an application In order to create an application type this command in your command line:

grails create-app project-creator

Output:

Created Grails Application at /home/josdem/Temporal/Grails/project-creator

Grails will create an directory named as the application name, go to that directory and continue creating a domain

Creating a domain

Grails create a relation between domain classes and a table in a database, this is known as ORM (Object-relational Mapping) and Grails uses Hibernate for this.

In order to create a domain named Project type this command in your command line:

grails create-domain-class com.josdem.Project

Output:

Created file grails-app/domain/com/josdem/Project.groovy
Created file test/unit/com/josdem/ProjectSpec.groovy

Grails validation capability is build on Spring’s validator API. However Grails takes this further and provides a unified way to define validation “constraints” with its constraints mechanism.

package com.josdem

class Project {
  String name

  static constraints = {
    name blank:false,size:1..15
  }
}

In this case we are validating in Project that name can not be blank and its size is between 1 and 15 characters

Scaffolding

Scaffolding lets you generate some basic CRUD interfaces for a domain class, including:

• The necessary views
• Controller actions for create/read/update/delete (CRUD) operations

Creating a controller

In order to create a controller we need to start grails application, type this:

grails

And then:

run-app

Output:

Server running. Browse to http://localhost:8080/project-creator
Application loaded in interactive mode. Type 'stop-app' to shutdown.
Enter a script name to run. Use TAB for completion:

Now we can create a controller named ProjectController type this command in your command line:

create-scaffold-controller com.josdem.Project

Output:

Created file grails-app/controllers/com/josdem/ProjectController.groovy
Created file grails-app/views/project
Created file test/unit/com/josdem/ProjectControllerSpec.groovy

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