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In 2009 I published a two-part series of articles on IBM developerWorks entitled Groovier Spring. The articles showed how Spring supports implementing beans in Groovy whose behavior can be changed at runtime via the "refreshable beans" feature. This feature essentially detects when a Spring bean backed by a Groovy script has changed, recompiles it, and replaces the old bean with the new one. This feature is pretty powerful in certain scenarios, for example in PDF generation; mail or any kind of template generation; and as a way to implement runtime modifiable business rules. One specific use case I showed was how to implement PDF generation where the Groovy scripts reside in a database, allowing you to change how PDFs are generated by simply updating Groovy scripts in your database.

In order to load Groovy scripts from a database, I showed how to implement custom ScriptFactoryPostProcessor and ScriptSource classes. The CustomScriptFactoryPostProcessor extends the default Spring ScriptFactoryPostProcessor and overrides the convertToScriptSource method to recognize a database-based script, e.g. you could specify a script source of database:com/nearinfinity/demo/GroovyPdfGenerator.groovy. There is also DatabaseScriptSource that implements the ScriptSource interface and which knows how to load Groovy scripts from a database.

In order to put these pieces together, you need to do a bit of configuration. In the articles I used Spring 2.5.x which was current at the time in early 2009. The configuration looked like this:

<bean id="dataSource"
  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <!-- set data source props, e.g. driverClassName, url, username, password... -->
</bean>

<bean id="scriptFactoryPostProcessor"
  class="com.nearinfinity.spring.scripting.support.CustomScriptFactoryPostProcessor">
    <property name="dataSource" ref="dataSource"/>
</bean>

<lang:groovy id="pdfGenerator"
  script-source="database:com/nearinfinity/demo/DemoGroovyPdfGenerator.groovy">
    <lang:property name="companyName" value="Database Groovy Bookstore"/>
</lang:groovy>

In Spring 2.5.x this works because the <lang:groovy> tag looks for a Spring bean with id "scriptFactoryPostProcessor" and if one exists it uses it, if not it creates it. In the above configuration we created our own "scriptFactoryPostProcessor" bean for <lang:groovy> tags to utilize. So all's well...until you move to Spring 3.x at which point the above configuration no longer works. This was pointed out to me by João from Brazil who tried the sample code in the articles with Spring 3.x, and it did not work. After trying a bunch of things, we eventually determined that in Spring 3.x the <lang:groovy> tag looks for a ScriptFactoryPostProcessor bean whose id is "org.springframework.scripting.config.scriptFactoryPostProcessor" not just "scriptFactoryPostProcessor." So once you figure this out, it is easy to change the above configuration to:

<bean id="org.springframework.scripting.config.scriptFactoryPostProcessor"
  class="com.nearinfinity.spring.scripting.support.CustomScriptFactoryPostProcessor">
    <property name="dataSource" ref="dataSource"/>
</bean>

<lang:groovy id="pdfGenerator"
  script-source="database:com/nearinfinity/demo/DemoGroovyPdfGenerator.groovy">
    <lang:property name="companyName" value="Database Groovy Bookstore"/>
</lang:groovy>

Then, everything works as expected and the Groovy scripts can reside in your database and be automatically reloaded when you change them. So if you download the article sample code as-is, it will work since the bundled Spring version is 2.5.4, but if you update to Spring 3.x then you'll need to modify the configuration in applicationContext.xml for example #7 (EX #7) as shown above to change the "scriptFactoryPostProcessor" bean to be "org.springframework.scripting.config.scriptFactoryPostProcessor." Note there is a scheduled JIRA issue SPR-5106 that will make the ScriptFactoryPostProcessor mechanism pluggable, so that you won't need to extend the default ScriptFactoryPostProcessor and replace the default bean, etc. But until then, this hack continues to work pretty well.

Selenium.prototype.setupProtoypeJS = function() {
    id = selenium.browserbot.getCurrentWindow().$;
    css = selenium.browserbot.getCurrentWindow().$$;
}

public void waitForPage() {
    selenium.waitForPage('60000')
    proc.doCommand('setupPrototypeJS', [])
}

selenium.click("dom=id('foo')")
selenium.click("dom=css('.bar')")
selenium.click("dom=css('span.foo a.baz')")

selenium = new DefaultSelenium(...)
selenium.setExtensionJs('...')
selenium.start()

selenium.setExtensionJs('''
        id = function(value) {
            return selenium.browserbot.getCurrentWindow().$(value);
        } 

        css = function(value) {
            return selenium.browserbot.getCurrentWindow().$$(value);
        }
''');

selenium.click("dom=id('foo')")
selenium.click("dom=css('.bar')")
selenium.click("dom=css('span.foo a.baz')")

A recent project started out life as an all-Java project that used Maven as the build tool. Initially we used Atlassian Clover to measure unit test coverage. Clover is a great product for Java code, but unfortunately it only works with Java code because it works at the Java source level. (This was the case as of Spring 2009, and I haven't checked since then.) As we started migrating existing code from Java to Groovy and writing new code in Groovy, we started to lose data about unit test coverage because Clover does not understand Groovy code. To remedy this problem we switched from Clover to Cobertura, which instruments at the bytecode level and thus works with Groovy code. Theoretically it would also work with any JVM-based language but I'm not sure whether or not it could handle something like Clojure or not.

In any case, we only cared about Groovy so Cobertura was a good choice. With the Cobertura Maven plugin we quickly found a problem, which was that even though the code coverage was running, the reports only showed coverage for Java code, not Groovy. This blog shows you how to display coverage on Groovy code when using Maven and the Cobertura plugin. In other words, I'll show how to get Cobertura reports to link to the real Groovy source code in Maven, so you can navigate Cobertura reports as you normally would.

The core problem is pretty simple, though it took me a while to figure out how to fix it. Seems to be pretty standard in Maven: I know what I want to do, but finding out how to do it is the really hard part. The only thing you need to do is tell Maven about the Groovy source code and where it lives. The way I did this is to use the Codehaus build-helper-maven-plugin which has an add-source goal. The add-source goal does just what you would expect; it adds a specified directory (or directories) as a source directory in your Maven build. Here's how you use it in your Maven pom.xml file:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <executions>
        <execution>
            <phase>generate-sources</phase>
            <goals>
                <goal>add-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>src/main/groovy</source>
                </sources>
            </configuration>
        </execution>
    </executions>
</plugin>

In the above code snippet, we're using the "build-helper-maven-plugin" to add the src/main/groovy directory. That's pretty much it. Run Cobertura as normal, view the reports, and you should now see coverage on Groovy source code as well as Java.

My current project (a web application) has a module that is almost entirely written in Groovy.  Note: We are using the latest version 1.6.5 of Groovy.

In one of the methods we had some logic similar to the following:

if (listOfThings && listOfThings.size < 0) {
    //Do my logic
}