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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

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

Now you can explore your the application and the scaffolding

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