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Create and test a Grails 3 TagLib; integrate the Trix WYSWYG editor

Learn how to integrate Trix (the rich text editor created by Basecamp) with your Grails app with the help of a custom TagLib

Authors: Sergio del Amo

Grails Version: 3.3.1

1 Grails Training

Grails Training - Developed and delivered by the folks who created and actively maintain the Grails framework!.

2 Getting Started

In this guide you are going to integrate a third party WYSWYG editor into your Grails 3 application with the help of a TagLib.

2.1 What you will need

To complete this guide, you will need the following:

  • Some time on your hands

  • A decent text editor or IDE

  • JDK 1.7 or greater installed with JAVA_HOME configured appropriately

2.2 How to complete the guide

To get started do the following:


The Grails guides repositories contain two folders:

  • initial Initial project. Often a simple Grails app with some additional code to give you a head-start.

  • complete A completed example. It is the result of working through the steps presented by the guide and applying those changes to the initial folder.

To complete the guide, go to the initial folder

  • cd into grails-guides/grails-taglib-wyswyg-trix/initial

and follow the instructions in the next sections.

You can go right to the completed example if you cd into grails-guides/grails-taglib-wyswyg-trix/complete

3 Writing the Application

3.1 Domain Class

Create a persistent entity to store Announcement entities. Most common way to handle persistence in Grails is the use of Grails Domain Classes:

A domain class fulfills the M in the Model View Controller (MVC) pattern and represents a persistent entity that is mapped onto an underlying database table. In Grails a domain is a class that lives in the grails-app/domain directory.

 ./grailsw create-domain-class Announcement
| Created grails-app/domain/demo/Announcement.groovy
| Created src/test/groovy/demo/AnnouncementSpec.groov
package demo

class Announcement {

    String title
    String message

    static constraints = {
        title maxSize: 255

    static mapping = {
        message type: 'text'

3.2 Scaffolding

Generate static scaffolding (Controller and Views) for the Domain class you created in the previous section.

 ./grailsw generate-all Announcement
| Created grails-app/domain/demo/Announcement.groovy
| Created src/test/groovy/demo/AnnouncementSpec.groov
Learn more about scaffolding in the Grails documentation.

3.3 Downloading Trix

Trix Editor is an open-source rich text editor project developed by Basecamp.

Compose beautifully formatted text in your web application. Trix is an editor for writing messages, comments, articles, and lists—the simple documents most web apps are made of. It features a sophisticated document model, support for embedded attachments, and outputs terse and consistent HTML.


To integrate into a Grails application:

  • Download the latest stable release. For this guide, we use version 0.10.0

  • Copy trix.js to assets/javascripts/trix.js

  • Copy trix.css to assets/javascripts/trix.css

  • Reference js and css files with Asset Pipeline Plugin

The Asset-Pipeline is a plugin used for managing and processing static assets in JVM applications primarily via Gradle (however not mandatory). Asset-Pipeline functions include processing and minification of both CSS and JavaScript files

Include the js file with Asset pipeline:

//= require trix

Include the css file with Asset pipeline:

*= require trix

3.4 Writing the Taglib

A tag library fulfills role of "view helper" in the Model View Controller (MVC) pattern and helps with GSP rendering. In Grails a tag library is a class with a name that ends in the convention "TagLib" and lives in the grails-app/taglib directory. Use the create-tag-lib command create a tag library _

./grailsw create-taglib Trix

The TagLib integrates Trix with forms as described in their documentation:

package demo

class TrixTagLib {
    static namespace = 'trix' (1)
    static defaultEncodeAs = [taglib: 'text'] (2)

    def editor = { attrs, body ->
        def id = ?:

        out << "<input id=\"${id}\" type=\"hidden\" name=\"${}\""
        if ( attrs.value ) {
            out << " value=\"${attrs.value.encodeAsHTML()}\""  (2)
        out << ' />'
        out << "<trix-editor input=\"${id}\"></trix-editor>"
1 We use a custom name space; trix
2 By default we encode as Text but the value, if present, is encoded as Html

And we test the TagLib:

package demo

import grails.testing.web.taglib.TagLibUnitTest
import spock.lang.Specification

 * See the API for {@link grails.test.mixin.web.GroovyPageUnitTestMixin} for usage instructions
@SuppressWarnings(['LineLength', 'MethodName'])
class TrixTagLibSpec extends Specification implements TagLibUnitTest<TrixTagLib> {

    void 'test trix editor markup is created'() {
        def expected = '''<input id="x" type="hidden" name="content" value="Editor content goes here" /><trix-editor input="x"></trix-editor>'''
        def output = applyTemplate('<trix:editor name="content" id="x" value="Editor content goes here"/>') (1)

        output == expected

    void 'trix editor value and id parameters are optional'() {
        def expected = '<input id="messsage" type="hidden" name="messsage" /><trix-editor input="messsage"></trix-editor>'

        tagLib.editor(name: 'messsage') == expected (2)
1 applyTemplate gets as an argument anything that would be valid in a GSP. That code gets evaluated as if it were in a GSP and what’s get returned is the result of evaluating that.
2 Because this test is annotated with @TestFor(TrixTagLib) the compiler will add a property called tagLib. You can interact with that tagLib property and invoke editor tag as it were a method. You could pass a map which will be passed to the args or a closure as the last method parameter which will be used as the body of the tag.

3.5 Use the Taglib

Use Trix in create and edit GSPs. Those were generated with the static scaffolding generate-all command.


<f:all bean="announcement"/>


<f:all bean="announcement" except="message"/>
<div class="fieldcontain required">
    <label for="message">
        <g:message code="announcement.message" default="Message"/>
        <span class="required-indicator">*</span>
    <trix:editor name="message" value="${announcement.message}"/>
<f:all bean="announcement" except="message"/>
<div class="fieldcontain required">
    <label for="message">
        <g:message code="announcement.message" default="Message"/>
        <span class="required-indicator">*</span>
    <trix:editor name="message" value="${announcement.message}"/>

4 Running the Application

To run the application use the ./gradlew bootRun command which will start the application on port 8080.

To run the tests:

grails> test-app
grails> open test-report


./gradlew check
open build/reports/tests/index.html

5 Do you need help with Grails?

Object Computing, Inc. (OCI) sponsored the creation of this Guide. A variety of consulting and support services are available.

OCI is Home to Grails

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