what is a cool use of groovy

[Jeanne Boyarsky]

I'm curious what cool uses people have found for Groovy. (beyond a Grails app)

MIne is being able to write Hudson/Jenkins scripts to run in the Groovy console. It's awesome being able to fix the parent jobs of hundreds of projects in just a few lines of code. Or write queries/reporting in just a few lines of code.

[Bear Bibeault]

Don't know how cool it is, but the Play! framework (version 1) templates use Groovy rather than JSP. (Version 2 uses Scala templates.)

[Jeanne Boyarsky]

Bear Bibeault wrote:Don't know how cool it is, but the Play! framework (version 1) templates use Groovy rather than JSP. (Version 2 uses Scala templates.)

So people can put too much Groovy code in the template instead of too much Java code?

[Kenneth A. Kousen]

Here's a one-liner to amuse your friends. Get the URL of their web site, open up a Groovy console, and do this:

println 'https://coderanch.com/forums'.toURL().text

The result prints the HTML code from the web site. That's one step away from accessing a RESTful web service. I have lots of examples like that.

Ken

[Bear Bibeault]

Jeanne Boyarsky wrote:

Bear Bibeault wrote:Don't know how cool it is, but the Play! framework (version 1) templates use Groovy rather than JSP. (Version 2 uses Scala templates.)

So people can put too much Groovy code in the template instead of too much Java code?

LOL! Yeah, those without discipline can create really poor templates. But in a lot of ways it's very very cool.

Two things I really like:

The "Elvis" operator: ?: (great for supplying defaults on false/null).

"Safe nav" operator: short-circuits null references. The expression user?.company?.address?.city produces null, rather than an NPE, if any reference is null.

[Kenneth A. Kousen]

Speaking of the Elvis operator, try this one:

def strings = ['this', 'is', 'a', 'list', 'of', 'strings']
strings.sort { s1, s2 ->
    s1.size() <=> s2.size() ?: s1 <=> s2
}

That's a sort by length, and if the lengths are equal (i.e., the sizes are the same so <=> returns 0), it sorts lexicographically (which is alphabetically with capital letters ahead of lowercase letters). More importantly, it shows Elvis being carried back to his home planet by two tandem spaceships, so it's the fat Elvis from the 70s rather than the thin Elvis from the 50s.

Yeah, that's a long way to go for such a silly gag, but I still find it amusing. More generally, if you wanted to sort strings by length in Java, you'd write:

Collections.sort(strings, new Comparator<String>() {
    public int compare(String s1, String s2) {
        return s1.length() - s2.length();
    }
});
assert strings*.size() == [1, 2, 2, 4, 4, 7]

The Groovy JDK adds a sort method to collections, so you don't need the Collections class at all. The sort method also takes a one- or two-argument closure. If you use the two-arg closure, you supply a typical comparator, as in:

strings.sort { s1, s2 -> s1.size() <=> s2.size() }

If you use the one-arg closure, then just return something that can be used for the sort (typically an integer), so the whole length sort reduces to:

strings.sort { it.size() }

and you're done. Hard to be much simpler than that.

[Jeanne Boyarsky]

Very cool. Thanks Ken!

[Pavel Sok]

We use groovy as additional logic in jasperreports (so-called scriptlets) and in testing. That's all, unfortunately. Nobody wants to use it in production in our team..

[chris webster]

Does Gradle count?