Scaffolding

What is Scaffolding?

Scaffolding allows you to auto-generate a whole application for a given domain class including:

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

Enabling Scaffolding

The simplest way to get started with scaffolding is to enable scaffolding via the "scaffold" property. For the "Book" domain class, you need to set the "scaffold" property on a controller to true:

class BookController {
   def scaffold = true
}

def scaffold = Author

• list
• show
• edit
• delete
• create
• save
• update

If you prefer to keep your domain model in Java and mapped with Hibernate you can still use scaffolding, simply import the necessary class and set the scaffold property to it.

Dynamic Scaffolding

Because Grails does not use code templates to achieve this you can add your own actions to the scaffolded controller that interact with the scaffolded actions. For example, in the below example, changeAuthor redirects to the show action:

class BookController {
   def scaffold = Book
   def changeAuthor = {
        def b = Book.get( params["id"] )
        b.author = Author.get( params["author.id"] )
        b.save()
        // redirect to a scaffolded action
        redirect(action:show)
   }
}

class BookController {
   def scaffold = Book
   // overrides scaffolded action to return both authors and books
   def list = {
         [ "books" : Book.list(), "authors": Author.list() ]
   }
}

Overriding Default Scaffolding

If you decide you don't like the default look and feel of the scaffolding, or want modify the default behavior of the scaffold code, you have the option of installing the scaffolding to your project, then tweak it there. To install the scaffolding code to your project type:

grails install-templates

Generating Static Controllers & Views

The above scaffolding features are useful but in real world situations its likely that you will want to customize the logic and views. Grails allows you to generate a controller and the views used to create the above interface via the command line. To generate a controller type:

grails generate-controller

grails generate-views

grails generate-all

Customising the Generated views

The views that Grails generates have some form of intelligence in that they adapt to the Validation constraints. For example you can change the order that fields appear in the views simply by re-ordering the constraints in the builder:

def constraints = {
      title()
      releaseDate()
}

def constraints = {
      title()
      category(inList:["Fiction", "Non-fiction", "Biography"])
      releaseDate()
}

def constraints = {
        age(range:18..65)
}

def constraints = {
        name(length:0..30)
}

def constraints = {
        description(widget:'textarea')
}

Java Integration

If your domain model is written in Java and mapped with Hibernate you can still take advantage of Grails' scaffolding mechanism. For the purpose of this documentation it is assumed you have read how Grails' Hibernate integration works in the section on GORM, needless to say to scaffold a hibernate domain class simply reference the domain class in the controller:

import com.books.HibernateBook
class BookController {
     def scaffold = HibernateBook
}

To integrate with the Grails constraints mechanism and hence hook into useful things like the way the views are generated and Grails' Validation mechanism you can do so by creating a Groovy script following the naming convention of your domain class and ending in the "Constraints" suffix. For example for the "HibernateBook" class defined above you would need to create a "com/books/HibernateBookConstraints.groovy" script in the same package is the class itself. Within the script just define constraints in the same way as you would do in a GORM class but without the {{def}} or {{static}} keywords before the name:

constraints = {
      title(length:5..15)
      desc(blank:false)
}