(Quick Reference)

9 Traits

Version: 3.3.2

9 Traits

Overview

Grails provides a number of traits which provide access to properties and behavior that may be accessed from various Grails artefacts as well as arbitrary Groovy classes which are part of a Grails project. Many of these traits are automatically added to Grails artefact classes (like controllers and taglibs, for example) and are easy to add to other classes.

9.1 Traits Provided by Grails

Grails artefacts are automatically augmented with certain traits at compile time.

Domain Class Traits

Interceptor Trait

Tag Library Trait

Service Trait

Below is a list of other traits provided by the framework. The javadocs provide more detail about methods and properties related to each trait.

Trait Brief Description

grails.web.api.WebAttributes

Common Web Attributes

grails.web.api.ServletAttributes

Servlet API Attributes

grails.web.databinding.DataBinder

Data Binding API

grails.artefact.controller.support.RequestForwarder

Request Forwarding API

grails.artefact.controller.support.ResponseRedirector

Response Redirecting API

grails.artefact.controller.support.ResponseRenderer

Response Rendering API

grails.validation.Validateable

Validation API

9.1.1 WebAttributes Trait Example

WebAttributes is one of the traits provided by the framework. Any Groovy class may implement this trait to inherit all of the properties and behaviors provided by the trait.

src/main/groovy/demo/Helper.groovy
package demo

import grails.web.api.WebAttributes

class Helper implements WebAttributes {

    List<String> getControllerNames() {
        // There is no need to pass grailsApplication as an argument
        // or otherwise inject the grailsApplication property.  The
        // WebAttributes trait provides access to grailsApplication.
        grailsApplication.getArtefacts('Controller')*.name
    }
}

The traits are compatible with static compilation…​

src/main/groovy/demo/Helper.groovy
package demo

import grails.web.api.WebAttributes
import groovy.transform.CompileStatic

@CompileStatic
class Helper implements WebAttributes {

    List<String> getControllerNames() {
        // There is no need to pass grailsApplication as an argument
        // or otherwise inject the grailsApplication property.  The
        // WebAttributes trait provides access to grailsApplication.
        grailsApplication.getArtefacts('Controller')*.name
    }
}