An update in the minor version does not seem like a big step but this is one brought a lot of changes, so here a step by step guide which highlights some pitfalls.
First update the version of Grails in your application properties:
app.grails.version=2.3.8
The tomcat and hibernate plugins now have versions of their respective frameworks and not the version number of Grails:
plugins.tomcat=7.0.52.1 plugins.hibernate=3.6.10.13
Grails 2.3 has a new databinding mechanism. To use the old one, especially if you use custom property editors you have to add this option to your Config.groovy:
grails.databinding.useSpringBinder = true
But even with the old databinding something changed. The field id is not bound in command objects you need to bind id explicitly:
def action = { MyCommand command ->
command.id = params['id']?.toLong()
}
Besides the databinding mechanism also the dependency resolving changed. But you can use the old ivy mechanism by including this in BuildConfig.groovy:
grails.project.dependency.resolver="ivy"
Nonetheless all dependencies must be declared in application.properties or BuildConfig.groovy. If you have a lib directory with local jars in your application you need to add this to your repositories as a local directory:
grails.project.dependency.resolution = {
repositories {
flatDir name:'myRepo', dirs:'lib'
}
}
When you have all dependencies declared your application should start.
Tests
Grails 2.3 features a new test mode: forking. This causes some problems and is better to be deactivated in BuildConfig.groovy:
grails.project.fork = [
test: false,
]
With the new version only JUnit4 style tests are supported. This means that you don’t extend GroovyTestCase or GrailsUnitTestCase. All rules must be public and non static. All tests methods need to be annotated with @Test. Set up methods are annotated with @Before and must be public. The tearDown methods must also be annotated with @After and be public. A bug in Grails prevents you from naming the set up and tear down methods freely: the names must be setUp and tearDown. All test methods must be public void, the old def declaration is not supported anymore. Now without extending GroovyTestCase you lose the assertion methods and need to add a static import:
import static groovy.util.GroovyTestCase.*
Unit Tests
All tests should be annotated with @TestMixin([GrailsUnitTestMixin]). If you need to mock domain classes you change mockDomain to @Mock:
class MyTest {
public void testThis() {
mockDomain(MyDomainClass, [mdc])
}
}
@Mock([Proposal])
class MyTest {
public void testThis() {
mdc.save()
}
}
Configuration is now already mocked and your properties can be added easily:
config.my.property.value.is='123'
Integration tests
As mentioned before setUp method naming has a bug: you have to name them setUp otherwise the changes to your database aren’t rollbacked.
Acceptance Tests with Selenium
You need to patch the Remote Control Plugin because of a ClassNotFoundException. Add an additional constructor to RemoteControl.groovy to support setting the classloader:
RemoteControl(ClassLoader loader) {
super(new HttpTransport(getFunctionalTestReceiverAddress(), loader), loader)
}
In your tests you call this new constructor with the classloader of your class:
new RemoteControl(getClass().classLoader)
Using a Groovy Mixin in your application does not work in your tests and need to be replaced with grails.util.Mixin. But this only works in one way: the target class can access the mixin but the mixin not the target class. For this to work you need to let your mixin implement MixinTargetAware and declare a field named target:
class MyMixin implements MixinTargetAware {
def target
}
Subtle changes and pitfalls
If you have a classname with a Controller suffix and a corresponding test but which isn’t a Grails controller Grails nevertheless tries to mock the class in your unit tests. If you rename the test to something without controller everything works fine.
In our pre 2.3 project we had some select tags in our views and used fieldValue for the selection:
<g:select value="${fieldValue(bean: object, field: 'value')}">
But now the select tag uses equals which fails if the values aren’t Strings. Just use the unescaped value:
<g:select value="${object?.value}">
I hope this guide and hints help others to avoid the headaches when upgrading your Grails application.
Schneide Blog 