Ted Naleid

Groovy 1.6.1 was released today, and it includes a patch I submitted a few weeks ago to make working with regular expressions much more groovy. Thanks to everyone that voted for the patch in the Groovy JIRA.

The main functionality is the addition of a variety of find and findAll regular expression aware methods that have been added to string.
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I just submitted a groovy patch that enhances the String class with a “find” method that makes working with regular expressions much easier.

One of the most common use cases is to search a string for a regular expression pattern. If a match is found, then do something with the matched value.
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Late last night, I ran across Tropo, a new IVR platform by Voxeo that supports a large variety of modern scripting languages, including my current favorite, Groovy (it also supports JavaScript, Ruby, Python, Jython, and PHP).

They just opened their “early beta” to the public about 10 days ago and have free accounts for developers to try things out.

They also have a github repository with a bunch of sample applications, and the adapter code that they’re using to make their core functionality available to all these different languages.

It’s nice to see an IVR company support all these modern things. VoiceXML has been rotting in a dungeon for the last 5 years and making a programming language out of an XML syntax was wrongheaded to begin with. Bringing languages like Groovy to bear on IVR problems will enable much more robust applications and quickent development.

Tropo’s documentation is a good start, but there are a number of holes in it since it’s so new. Because we have access to all of the yummy Groovy metaprogramming and reflection, we can find out lots of information about the system and it’s functionality for ourselves.

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I’ve just opened JIRA issue with a patch to enhance the groovy and grails consoles so that the default font size and the dimensions of the input and output areas can be overridden.

The initial patch I submitted used a custom GroovyConfig file, but at the suggestion of Guillame, I’ve modified the patch to use the preferences API. In my initial poke through the code, I didn’t see the preferences API being used (and couldn’t remember any settings that were saved by the console). After a closer look, it was being used in a couple of places.

The updated patch has been accepted and scheduled for inclusion in Groovy 1.6.1.

If you’re interested in making sure this change gets in, please vote for the JIRA.

I know that I open a groovy or grails console probably 10 times on an average day of programming, and the first thing that I do every time is to hit cmd-shift-L 3 times to bump the font size up to 18 points (yes, my eyes aren’t that great and I’m running my monitor at 1920×1200). The next thing that I do is drag it from the postage stamp size that it defaults to to cover at least half my screen.

This patch will probably save me more frustration than time, but I’m hoping it’ll save a lot of both for others out there.

This change won’t get in till 1.6.1, so if you want to tweak your current groovy install, it’s actually pretty easy to do.
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The January 2009 issue of GroovyMag was released today. In it, I’ve written an article that shows how easy regular expressions are to use in groovy. It starts with some regular expression basics, shows some common idiomatic groovy usage patterns and wraps up with some of the cool new features that groovy 1.6 is adding to regexp handling.

There are over 30 code samples in then article and I wanted to make sure while writing and editing that all of the code samples ran exactly as they appeared in the article text. Also, when you download an issue of GroovyMag, you get a zip file that has a PDF and a set of code “listing” files for each article. Each listing file contains a snippet of groovy code that appeared in the issue.

I decided to write a couple of simple groovy scripts to keep things DRY, and to ensure that my edits didn’t break anything. The first script extracts code listings out of my draft article and saved them to individually numbered listing files. The second script executes each of the listing files and reported success or failure for each. Sort of a poor man’s JUnit for writing articles.

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So groovy has this cool operator called the “spread” operator: “*.”.

Right now, it’s listed as the top hidden feature of Groovy over on StackOverflow. It works like this:

[1, 2, 3, 4]*.toString() 
// equals ["1", "2", "3", "4"]

It applies the method/property to the right of the operator to each member of the collection and returns the results as another collection. It’s syntactic sugar for doing this:

[1, 2, 3, 4].collect { item -> item.toString() }

(and that’s syntactic sugar for a whole pile of Java code :)

Did you know that for properties, you don’t actually need to use the spread operator? Neither did I till I fat-fingered a command working with a list of Grails domain objects and it still worked.
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In my current project, I’ve been doing a lot of tweaking of the default grails scaffolding templates. Because of this, I need to run the new uber generate-all command quite a bit to recreate things.

The one problem with this script is that if the files already exist, a prompt will come up after ~10 seconds or so (after the grails environment bootstraps) asking you if you want to Overwrite everything:

grails generate-all "*" 
...
~10 seconds pass
...
Generating views for domain class Baz ...
File /foobar/grails-app/views/baz/list.gsp already exists. Overwrite?y,n,a

This was a bit of a pain as I’d often kick the script off, get distracted and then come back to the shell with that prompt still waiting for me to tell it what to do. I’d rather just start working with my shiny new scaffolding.

The easy solution to this is simply to pipe the answer you want into the grails command:

echo "a" | grails generate-all "*"

Doing that will pipe the “a” into the grails command so that when the prompt finally comes up, it knows that it can continue regenerating all of my scaffolding.

It seems simple enough after I figured it out, but I thought it could save some other people time when they’re hacking around with templates and know they want to regenerate all of them.
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Out of the box, groovy gives you a number of powerful methods to iterate over lists and maps:

def fibList = [1, 1, 2, 3, 5]
 
fibList.each { println it }  // prints all of the numbers in the list
assert fibList.any { it == 3 }
assert fibList.every { it > 0 }
assert fibList.collect { it - 1 } == [0, 0, 1, 2, 4]
assert fibList.findAll { it > 1 && it < 5 } == [2, 3]
assert fibList.find { it > 1 } == 2
assert fibList.inject("fib: ") { str, val -> str < < val }.toString() == "fib: 11235"

That’s really nice if you’re working with raw lists and maps, but what if you have a class that doesn’t extend list or map? How hard is it to empower that class with the groovy iteration methods? If this were Java, you’d likely need to implement an interface with these methods (and throw a “not implemented” exception for those you didn’t feel like taking the time to implement).

Since it’s not Java, but groovy (and you’ve read the title of this blog post :), you know it’s easy!
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Over on the RailsEnvy blog (the guys who made the “Rails vs. X commercials” last year), there’s an article that highlights some of the nice syntactic sugar that Groovy has that’s currently not available in Ruby.

I actually came to Groovy/Grails after working with Ruby/Rails for about a year. Both languages and framworks have their strengths and it’s nice to see cross-pollination of good ideas going both ways. From the comments, it sounds like Ruby 1.9 is getting some of the features that we’ve had in Groovy for a while.
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UPDATE: if you’re using Groovy 1.6.1 or greater (released April 2009), check out the new find and find all methods in this post.

Some people, when confronted with a problem, think “I know, I’ll use regular expressions!”
Now they have two problems. — Jaime Zawinski

There is a common and well-earned aversion in the Java world to regular expressions. Prior to Java 1.4, regular expressions weren’t even part of the core language. Post 1.4, using regular expressions is still a painful task of working with Pattern and Matcher objects. Lots of typing is involved to make anything happen. It’s difficult enough that most Java devs don’t end up using them enough to actually remember how to read a regular expression, and they need to dig up the JavaDocs (or cut and paste an old example), every time they want to use them.

This aversion has persisted into the Groovy community to a level that I haven’t seen in other dynamic scripting languages like Ruby, Python, and (obviously) Perl.

The current regexp docs that pop up when doing a google search are all outdated and don’t use any of the best techniques that are available in the groovy 1.5.X and 1.6-beta code that is now available. The recent Groovy Recipes book doesn’t have an entry for regular expressions in the index, and I was unable to find a single example of a regular expression in the entire book.

This is unfortunate because Groovy makes using regular expressions much easier than in Java. Under the covers, you’re still working with the same old Java Pattern and Matcher objects, but the Groovy syntax and additions to those classes are pleasant to work with.
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