Building Grails Plugins - Tips And Tricks

Building Grails Plugins
tips and tricks from the wild

About Me
• Mike Hugo, Independent Software Developer

• http://piragua.com

• http://WhenWorksForYou.com

• Groovy/Grails since 2007

• Author of several Grails plugins
• code-coverage • greenmail

• hibernate-stats • build-info

• test-template • ????

• Plugins overview
• Build your own plugin
• testing
• modularization
• conﬁguration
• events
• did I mention testing?

what’s on the menu for tonight?

App Plugin

a plugin is just another grails application, with a few extra ﬁles
* GrailsPlugin.groovy
* Install, Uninstall and Upgrade scripts

Cool hooks into the runtime environment of a running grails app, plus ability to add new
‘artefacts’ and participate in reloading events

Existing Plugins

there are a ton of existing plugins from security to Rich UI to searching to...you name it.

common problem - this is one i’ve solved about 6 times. time for a plugin

• grails create-plugin build-status
• cd build-status
• mkdir test/projects
• cd test/projects
• grails create-app statusapp
gives you a client you can
use to test your plugin.
why?

development
• make a change to the plugin
• grails package-plugin
• cd test/projects/statusapp/
• grails install-plugin ../../../grails-build-status-0.1.zip
• grails run-app
• wash, rinse, repeat

In Place Plugins
• In the application just created, modify
BuildConﬁg.groovy and add:
• grails.plugin.location."build-status" = "../../.."

• TADA! You’re now working with an in-
place plugin

Add Controller (test)
import grails.test.*

class BuildInfoControllerTests extends ControllerUnitTestCase {
void testIndex() {

! ! controller.index()
! !
! ! assertEquals('index', renderArgs.view)
! ! assertEquals(['app.version'],
renderArgs.model.buildInfoProperties)
}
}

Add Controller

class BuildInfoController {

! static final List infoProperties = ['app.version']

def index = {
! ! render view:'index', model:
[buildInfoProperties:infoProperties]
! }
}

Add the View
<html>
<head>
<title>Build Info</title>
</head>
<body>
<div>
<g:each in="${buildInfoProperties}" var="prop">
<g:if test="${g.meta(name:prop)}">
<tr>
<td>${prop}</td><td><g:meta name="${prop}"/></td>
</tr>
</g:if>
</g:each>

</div>
</body>
</html>

Functional Testing
• in the app, install the functional test plugin
• grails create-functional-test
class BuildInfoPageFunctionalTests extends
functionaltestplugin.FunctionalTestCase {
void testSomeWebsiteFeature() {
get('/buildInfo')
assertStatus 200
assertContentContains 'app.version'
assertContentContains 'app.grails.version'
}
}

Introduce i18n
• i18n allows a form of customization
• create a messages.properties in the plugin
i18n directory for default values
• override it in the app to test to make sure
it works

Introducing Conﬁg
• Allow the client application the ability to
add or remove properties to display

void testIndex_overrideDefaults(){
mockConfig """
buildInfo.properties.exclude = ['app.version']
buildInfo.properties.add = ['custom.property']
"""

controller.index()
assertEquals 'index', renderArgs.view

def expectedProperties = controller.buildInfoProperties - 'app.version'
expectedProperties = expectedProperties + 'custom.property'

assertEquals expectedProperties, renderArgs.model.buildInfoProperties
}

Modularizing Views
• Put contents of views into templates
• Allows client to override the default view
//view // template
<html> <g:each in="${buildInfoProperties}" var="
<head> <g:if test="${g.meta(name:prop)}">
<title>Build Info</title> <tr>
</head> <td>
<body> <g:message code="${prop}"/>
<div> </td>
<table> ! ! ! <td>
! <g:render template="info" <g:meta name="${prop}"/>
plugin="buildstatus"> </td>
</table> </tr>
</div> </g:if>
</body> </g:each>
</html>

Events
• We want to capture the start of WAR ﬁle
being built and log the Date/Time
• What events are available?
• Search $GRAILS_HOME/scripts for
“event”
• What variables are available?
• binding.variables.each {println it}
http://grails.org/doc/latest/guide/4.%20The%20Command%20Line.html#4.3%20Hooking
%20into%20Events

test it
• grails.test.AbstractCliTestCase
• Thank you Peter Ledbrook:
http://www.cacoethes.co.uk/blog/
groovyandgrails/testing-your-grails-scripts

http://grails.org/doc/latest/guide/4.%20The%20Command%20Line.html#4.3%20Hooking
%20into%20Events

import grails.test.AbstractCliTestCase
import java.util.zip.ZipFile

class CreateWarEventTests extends AbstractCliTestCase {

void testCreateWar(){
execute (['war', '-non-interactive'])

assertEquals 0, waitForProcess()

verifyHeader()

Properties props = new Properties()
props.load(new ZipFile('target/app-0.1.war').
getInputStream('WEB-INF/classes/application.properties'))

assertNotNull props['build.date']
}

}

eventCreateWarStart = {warname, stagingDir ->
Ant.propertyfile(file:
"${stagingDir}/WEB-INF/classes/application.properties") {
entry(key: 'build.date', value: new Date())
}
}

return the favor
• publish your own events to allow clients
to hook into plugin workﬂow

eventCreateWarStart = {warname, stagingDir ->
event("BuildInfoAddPropertiesStart", [warname, stagingDir])

Ant.propertyfile(file:
"${stagingDir}/WEB-INF/classes/application.properties") {
entry(key: 'build.date', value: new Date())
}

event("BuildInfoAddPropertiesEnd", [warname, stagingDir])
}

Gradle Build
• http://adhockery.blogspot.com/2010/01/
gradle-build-for-grails-plugins-with.html
• http://www.cacoethes.co.uk/blog/
groovyandgrails/building-a-grails-project-
with-gradle
• One build ﬁle in the plugin that runs tests
on all your ‘apps’ in the test/projects
directory

in-place plugin caveats
• Reloading plugin artifacts doesn’t always work

• Grails 1.1.1

• see next slide

• Grails 1.2.1

• Plugin controllers lose GrailsPlugin annotation
and views cannot be resolved after reloading
http://jira.codehaus.org/browse/GRAILS-5869

def watchedResources = ["file:${getPluginLocation()}/web-app/**",
"file:${getPluginLocation()}/grails-app/controllers/**/*Controller.groovy",
"file:${getPluginLocation()}/grails-app/services/**/*Service.groovy",
"file:${getPluginLocation()}/grails-app/taglib/**/*TagLib.groovy"
]

def onChange = { event ->
if (!isBasePlugin()) {
if (event.source instanceof FileSystemResource && event.source?.path?.contains('web-app')) {
def ant = new AntBuilder()
ant.copy(todir: "./web-app/plugins/PLUGIN_NAME_HERE-${event.plugin.version}") {
fileset(dir: "${getPluginLocation()}/web-app")
}
} else if (application.isArtefactOfType(ControllerArtefactHandler.TYPE, event.source)) {
manager?.getGrailsPlugin("controllers")?.notifyOfEvent(event)
// this injects the tag library namespaces back into the controller after it is reloaded
manager?.getGrailsPlugin("groovyPages")?.notifyOfEvent(event)
} else if (application.isArtefactOfType(TagLibArtefactHandler.TYPE, event.source)) {
manager?.getGrailsPlugin("groovyPages")?.notifyOfEvent(event)
} else if (application.isArtefactOfType(ServiceArtefactHandler.TYPE, event.source)) {
manager?.getGrailsPlugin("services")?.notifyOfEvent(event)
}
}
// watching is modified and reloaded. The event contains: event.source,
// event.application, event.manager, event.ctx, and event.plugin.
}

ConfigObject getBuildConfig() {
GroovyClassLoader classLoader = new GroovyClassLoader(getClass().getClassLoader())
ConfigObject buildConfig = new ConfigSlurper().parse(classLoader.loadClass('BuildConfig'))
return buildConfig
}

String getPluginLocation() {
return getBuildConfig()?.grails?.plugin?.location?.'PLUGIN_NAME_HERE'
}

the real deal

http://plugins.grails.org/grails-build-info/trunk/
source code available in the grails plugin svn repository, or browse on the web at:
http://plugins.grails.org/grails-build-info/trunk/

Building Grails Plugins - Tips And Tricks

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