What the F is f:table

Today I needed to knock up a quick interface to some database tables for inputting and editing data to be used in the demonstration of some data extraction software. Aha I thought; I’ll try using Grails Scaffolding. I haven’t used grails scaffolding in earnest since taking a grails training course few years back. However, today I really did just need some simple CRUD functionality.

In Grails 3, you have two options for scaffolding – annotating the controller and having the views and controller methods auto-generated at runtime, or running a command to generate them statically so that you can modify them. I chose the latter, assuming that I’d want to do some customisation.

grails generate-all com.domain.Thing

You can then inspect the generated controller and views, and make any changes necessary. And this is where it all started to go wrong. The table containing the list of existing records didn’t look very nice. I’d removed the default ‘application.css’ which comes with grails, and used bootstrap to style the app. Without the default styles, the table has no spacing, and looks pretty awful.

No problem, I just need to add class=”table” to the table and I’ll get a standard bootstrap styled table. However, the generated index.gsp doesn’t contain a table tag. All I found was this:

<f:table collection="${thingList}"/>

The <f:table/> tag was a new one to me. Google suggests this comes from the grails fields plugin, but the documentation is very sparse: Grails 3 fields plugin.
The documentation doesn’t even mention the <f:table/>http://grails3-plugins.github.io/fields/snapshot/ref/Tags/table.html which helped a bit, in that it showed how to configure which fields to show in the table but didn’t help in changing styles or other formatting.

The main grails scaffolding documentation suggests running

grails install-templates

to get local copies of the templates used in scaffolding, but this doesn’t include anything to do with the fields plugin.

More detective work led to this Stackoverflow post, and onward to the fields plugin source code.

Finally… how to customise the f:table tag:

Place a file called _table.gsp in /grails-app/views/templates/_fields/

The default file contents are here: _table.gsp

After adding this file to the project and amending to use the required styles, the <f:table/> tag can be used throughout the project with reckless abandon.

My table looks nice now, but I think this sums up why I struggle with the grails plugin ecosystem; it feels a bit half-finished to be using an undocumented tag as part of what should be a quick start process for new users.


Groovy Grails Exchange 2013

This week I attended the 2013 Groovy Grails Exchange, organised by Skills Matter (with whom I’ve also been lucky enough to attend a couple of courses over the years).

Finally got time to jot down a few thoughts – I came back with an almost full notebook, but these are the highlights:

1. What a great conference! Skills Matter did an amazing job of hosting. The speakers were varied and interesting. It was fantastically motivating to be amongst all these people who are actually pushing the technology forwards. As I work in a very small dev team (out in the sticks) I found it really interesting to see what goes on in the rest of the world.

2. Must. Learn. Spock.

3. Must also get back on board with Geb. I dabbled a little a while ago, and now that we’re about to start a new Grails project, functional testing with Spock & Geb has to be central to it. Lots of food for thought in the DevQA talk by Alvaro Sanchez-Mariscal, applicable even though we don’t have a dedicated QA team for our internal dev.

4. Forces on code – what makes code “good” depends on the context. Common sense really but well illustrated in the talk by by David the Coder

5. Do I need to learn a JavaScript framework? I enjoyed the very persuasive talk on Developing SPI Applications by Alvaro Sanchez-Mariscal. Separating the front end and back end into independent apps makes a lot of sense especially if you have dedicated UI developers. I’m not sure we have the resources to move away from GSPs just yet. But I’m certainly going to have a browse around ToDoMVC to get an idea of the options.

6. Jeff Brown’s live coding demo of Metaprogramming With The Groovy Runtime was a great refresher – nothing particularly that hadn’t been covered on the Groovy course I attended last year, but a reminder that I am pretty guilty of just writing Java like code inside .groovy files and not taking full advantage of groovy’s awesomeness.

7. The “Open Source and You” session by Peter Ledbrook made me think a bit more deeply about Open Source software – what to expect from it, the costs involved, how to manage a successful open source project. I’m definitely motivated to get more involved.

8. Gradle for deployment? @danveloper’s talk on Groovy for Sysadmins gave me lots to think about. I doubt I’ll ever end up hacking the kernel, but I like the software centric approach to deploying and maintaining servers.

9. Must pay more attention to release notes and road maps. New and upcoming versions of Groovy and Grails have some great new features that I’m looking forward to using. Changes notes for Groovy 2.2 and Grails 2.3 definitely worth a look. Also looking forward to plugin and build system changes in Grails 3.0 some time in 2014.

10. And finally, how come all these Open Source aficionados use Macs?! I’ve not got an iAnything yet and don’t plan to. Linux rocks :)

Anyway, in summary, well worth going for anyone working with Groovy or Grails. Podcasts of all the talks are available on the Skills Matter website, but I think attending in real is a fantastic opportunity to absorb knowledge from an enthusiastic and knowledgeable crowd, and worth every penny. Better get my early bird ticket for next year…


Unexpected side effects using Groovy MockFor in a Grails test

Recently, I was trying to write a Unit Test for a Grails method which instantiates an HTTPBuilder object within a method.

I couldn’t use the normal Grails ‘mockFor’ syntax, because the HTTBuilder was not injected or accessible from outside the class. No problem, because standard Groovy MockFor is also available.

With a bit of help from google (http://stackoverflow.com/questions/9101084/groovy-httpbuilder-mocking-the-response) I came up with the test below.

def testDoSomething() {
    def requestDelegate = [response: [:], uri: [:]]

    def mockHttpBuilder = new MockFor(groovyx.net.http.HTTPBuilder)
    mockHttpBuilder.demand.request { Method method, Closure body -&amp;gt;
        body.delegate = requestDelegate
        requestDelegate.response.success() // make it call success

    mockHttpBuilder.use {
        // All calls to HTTPBuilder will be intercepted within this block of code.      
        MyClient myClient = new MyClient();
        assert myClient.doSomething(&amp;quot;Some Param&amp;quot;)

This works really well in isolating the code under test from the HTTP request.

However after spending a bit of time working on this test, and getting it to pass, I ran test-app on the entire project, and was very confused to see that some totally unrelated tests had begin to fail. Grails was reporting errors like “No more calls to ‘get’ expected at this point.” in tests where I had used no mocking at all. I was bewildered.

Eventually I came across GRAILS-8535. Although unit tests are supposed to be just that, it seems that grails continues to use the proxy in subsequent tests. This appears to be fixed in Grails 2.2.3, but as of the time of writing, this wasn’t released.

Luckily, it is possible to manually reset the MetaClass in the Grails MetaClassRegistry at the end of the test.

At the start of the test which uses MockFor, I record what the class was originally:

MetaClassRegistry registry = GrailsMetaClassUtils.getRegistry()
def originalMetaClass = registry.getMetaClass(HTTPBuilder)

And at the end of the test, set it back:

MetaClassRegistryCleaner.addAlteredMetaClass(HTTPBuilder, originalMetaClass) 

Best method for functional testing in grails

or ‘why isn’t there more quality control on the internet…?’

This week I tried to add some automated functional tests to a grails project. (See my post on agile best practices; we agreed that our definition of ‘Done’ should definitely include functional tests)

There are a few plugins for grails which look like they could do the job.

My final selection criteria turned out to be: the only one which I could get working within less than half a day.

Canoo Webtest


I came away from a recent grails training course thinking that this was the de-facto standard for functional testing. In fact, I have since then used the standalone Webtest tool to test a legacy PHP application, with good success.

However, trying to get going in grails was a different matter.

:: net.sourceforge.htmlunit#htmlunit;2.8-SNAPSHOT: not found

I found the following bug report, and following the advice to specify the htmlunit version did allow me to get started.


But I was already disappointed.  If I install a plugin using the grails install-plugin command, I think there should be some level of assurance that the plugin version to be installed will be a tested version, dependent on NON-snapshot versions of any required libraries.

Grails functional-test plugin

I then realised that other plugins were available, as mentioned in the grails functional testing user guide.
The documentation for this one defines the dependency as

compile ":functional-test:2.0.RC1"

Again, I do not want the install-plugin command to install a Release Candidate. I want the tested and released version. I tried using an older version as well, but gave up on this pretty quickly too.


See: http://grails.org/plugin/selenium-rc
The grails plugin page states:

This plugin is no longer maintained. Consider looking at Geb.

So this is what I did.


After a bad day, I was pleasantly surprised to get going quickly with Geb. And I really like the separation between modelling the available functions on the page and calling them in tests. Although the plugin version is only 0.9.0 it feels like it is current and will be maintained.

I’m surprised at how much trouble I had getting going with functional testing. It feels like there is a lack of quality control on the publicly available Grails plugins, and little attempt to ensure versions are compatible with other standard plugins such as jQuery.

I’ll be spending some more time learning to use Geb in the near future, so I’ll try and report my progress…


Grails unit tests failing on jenkins

I spent a while confused today, when some fairly straightforward unit tests were running fine locally, but failing on our continuous integration server, jenkins.

The error was occurring in the setUp method, annotated @Before, where we were setting a flash variable prior to running tests.

java.lang.NullPointerException: Cannot invoke method getFlashScope() on null object
at grails.test.mixin.web.ControllerUnitTestMixin.getFlash(ControllerUnitTestMixin.groovy:159)

After much head scratching I came across this link
which explains a similar problem.

It appears that because the Controller uses a Mixin, it effectively extends ControllerUnitTestMixin which is not abstract and also has a method annotated with @Before. Junit does not guarantee the order in which the two methods annotated with @Before will be run (See http://junit.sourceforge.net/doc/faq/faq.htm#tests_2)

If the Mixin method does not run before my setUp method, the flash scope has not been mocked, hence the failure.

The solution suggested in the post is to call super.bindGrailsWebRequest() in the setUp method. In our case it was simple enough to set the flash variable within the individual tests, instead of the setUp method.


Updating from a list in Grails

This week I had the pleasure of attending both Groovy and Grails courses at Skills Matter in London. The courses were taught by Dierk König, a committer to both Groovy and Grails, and the author of Groovy in Action. He’s very knowledgeable and the courses were really interesting – I would have liked more time for advanced grails topics, but I guess you can’t fit it all in to two days!

During the course I asked for help with one of my pet grails problems – the best way to update multiple records at once from a list view. For example, you might have a set of records with a check box field, and want to tick/un-tick for several rows and then save all with a single click. We didn’t quite get it working in class, but I got some helpful advice which meant I was able to finish it off on the train home.

The domain class is nothing special:

class Person {
 String firstName
 String lastName
 boolean available

My PersonController looks like this (I’ve left the scaffolding in, so you get all the standard pages too):

class PersonController {
   static scaffold = true
   def multiEdit = {
      List<Person> list = Person.list()
      [personInstanceList: list]

    def multiSave = { MultiplePersonCommand command ->
     command.people.each { p ->
     Person person = Person.get(p.id)
     person.properties = p.properties
   redirect action: list
class SinglePersonCommand {
 Integer id
 boolean available
class MultiplePersonCommand {
 List<SinglePersonCommand> people = [].withDefault({ new SinglePersonCommand() } )

The important thing here is the use of Command objects. I’ve defined these in the same class as the Controller but they could be in a separate file. The really important tip is the use of `withDefault` on the list in the MultiplePersonCommand. When the binding takes place, we can’t guarantee what order it will be in. For example it might try to bind the second list item before the first. This would cause an error without the `withDefault` method.

And finally, multiEdit.gsp looks like this:

<g:form action="multiSave">
 <g:each var="person" in="${personInstanceList}" status="i">
     <div id="person${i}">
     <g:hiddenField name='people[${i}].id' value='$person.id'/>
     <g:fieldValue bean="${person}" field="firstName"/>
     <g:checkBox name='people[${i}].available' value='1' checked="${person.available}"/>
<g:submitButton name="action" />

The important thing here is the use of the $i variable in square brackets on the fields in question. This means that the params that come back to the Controller will effectively contain people[0].id, people[0].available, people[1].id, people[1].available and so on. Grails is clever enough to bind all the people[0] values to the first SinglePersonCommand in the people list inside the MultiplePersonCommand, and so on. Then I can access this list and copy across the values to People objects and save them.

I hope this is useful to someone. I’m looking forward to spending some time on Groovy and Grails development, so hopefully more here soon!