dependencies {
// ...
implementation "org.grails.plugins:scaffolding"
// ...
}19 Scaffolding
Version: 6.2.2
19 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
The way for an application to express a dependency on the scaffolding plugin is by including the following in build.gradle.
Dynamic Scaffolding
The simplest way to get started with scaffolding is to enable it by setting the scaffold property in the controller to a specific domain class:
class BookController {
static scaffold = Book // Or any other domain class such as "Author", "Publisher"
}With this configured, when you start your application the actions and views will be autogenerated at runtime. The following actions are dynamically implemented by default by the runtime scaffolding mechanism:
-
index
-
show
-
edit
-
delete
-
create
-
save
-
update
A CRUD interface will also be generated. To access this open http://localhost:8080/book in a browser.
Note: The old alternative of defining scaffold property:
class BookController {
static scaffold = true
}is no longer supported above Grails 3.0.
If you prefer to keep your domain model in Java and mapped with Hibernate you can still use scaffolding, simply import the domain class and set its name as the scaffold argument.
You can add new actions to a scaffolded controller, for example:
class BookController {
static 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)
}
}You can also override the scaffolded actions:
class BookController {
static scaffold = Book
// overrides scaffolded action to return both authors and books
def index() {
[bookInstanceList: Book.list(),
bookInstanceTotal: Book.count(),
authorInstanceList: Author.list()]
}
def show() {
def book = Book.get(params.id)
log.error("{}", book)
[bookInstance : book]
}
}All of this is what is known as "dynamic scaffolding" where the CRUD interface is generated dynamically at runtime.
| By default, the size of text areas in scaffolded views is defined in the CSS, so adding 'rows' and 'cols' attributes will have no effect. |
Also, the standard scaffold views expect model variables of the form <propertyName>InstanceList for collections and <propertyName>Instance for single instances. It’s tempting to use properties like 'books' and 'book', but those won’t work.
Static Scaffolding
Grails lets you generate a controller and the views used to create the above interface from the command line. To generate a controller type:
grails generate-controller Bookor to generate the views:
grails generate-views Bookor to generate everything:
grails generate-all BookIf you have a domain class in a package or are generating from a Hibernate mapped class remember to include the fully qualified package name:
grails generate-all com.bookstore.BookCustomizing the Generated Views
The views adapt to 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()
}You can also get the generator to generate lists instead of text inputs if you use the inList constraint:
def constraints = {
title()
category(inList: ["Fiction", "Non-fiction", "Biography"])
releaseDate()
}Or if you use the range constraint on a number:
def constraints = {
age(range:18..65)
}Restricting the size with a constraint also effects how many characters can be entered in the d view:
def constraints = {
name(size:0..30)
}The Fields Plugin
The Grails scaffolding templates make use of the The Fields Plugin. Once you’ve generated the scaffold views, you can customize the forms and tables using the Taglib provided by the plugin (see the Fields plugin docs for details).
<%-- Generate an HTML table from bookInstanceList, showing only 'title' and 'category' columns --%>
<f:table collection="bookInstanceList" properties="['title', 'category']"/>Customizing the Scaffolding templates
The templates used by Grails to generate the controller and views can be customized by installing the templates with the install-templates command.