Over the last couple months I’ve been taking a bit of spare time to write something that I hope all of us can benefit from: GroovyRTM

What is GroovyRTM?

GroovyRTM allows you to easily take advantage of the Remember The Milk REST API using any language on the JVM. In short, you can now write apps for Remember The Milk without having to worry about all the HTTP transaction stuff, error handling, etc. As its name implies, it’s written in Groovy, which made it much easier to write and test.

How can I use it?

To get started, you’ll need 3 things:

1. Download groovyrtm-all.jar from the project on GitHub
2. Request an API key (you’ll probably want an RTM account to test it with, too)
3. Create a RtmService.properties file as explained in the project Wiki

UPDATE: I’ve created a quick-start project that has everything you need to get started quickly! I included an application authorization example because that’s the first hurdle. Download it here

Just how easy is it? Suppose you want to write a little Java app that adds a new task:

import org.eriwen.rtm.*;

class MyGroovyRtmTest {
    public static void main(String[] args) {
        GroovyRtm rtm = new GroovyRtm("api-key", "shared-secret");
        rtm.testEcho();
    }
}

It’s that easy! Now, it’s a little deceiving because the first time your app runs you have to allow it access via the RTM website. The best part is… it’s open source! You can check out the source with Git:

git clone git://github.com/eriwen/groovyrtm.git

Awesome! Can I help?

Of course! Get the code, give me suggestions, use it and tell me what you think. I am willing to add people to the project that show me their interest and some good Groovy code. Just hit up the issue tracker or use my contact form for questions or suggestions.

If you think it’s cool but you can’t use it, help me get it out there by digging it or voting on your favorite aggregator.

Related posts:

1. Cheqlist: A free, open-source desktop app for Remember The Milk
2. Why I’m moving my projects to GitHub
3. What and why: the tech behind Cheqlist

A bit of Groovy background

A couple key features of Groovy are that everything is an object and that operators are just syntactic sugar for calling methods on the objects. What’s cool about this is that with Groovy you can override the default behavior of these operators for certain classes. For example, 4 + 2 in Groovy really means 4.plus(2)

How to implement/override operators in Groovy

Groovy allows you to override a LOT of stuff, including final methods and operators. If I want to override a method on the String class, all I need to do is:

String.metaClass.plus {
    //It is a special term for the argument passed (if there is only 1)
    String stringToEncode = it
    //delegate is a special term for the caller of the method
    delegate << URLEncoder.encode(it, 'UTF-8')
}

String first = "my delegate "
String second = "twitter @eriwen"
//prints "my delegate twitter+%40eriwen"
println first + second

Notice that it (intentionally) only encodes the second String. Check out the list of operators and associated methods. This is great, but I need to restrict this to code blocks I so choose. That’s where Groovy Categories come in.

Overriding with Categories

Groovy Categories allow you to add functionality to any class at runtime. This means that you can add in methods to final classes (like java.lang.String). In this case I just want to override a method instead of adding one.

class MyUtils {
  //Takes 2 java.lang.Strings and returns a String - TYPES ARE OPTIONAL
  static String plus(String first, String second) {
    //Concatenates the Strings and returns
    first << URLEncoder.encode(second, encoding)
  }
}

//my other class in another file...
import MyUtils

class MyOtherClass {
  String first = "first"
  String second = "to be encoded"
  use (MyUtils) {
    // This will now encode value
    list << first + second
  }
}

Note that Groovy defaults to GStrings, so you can’t just use def actuallyMyString.

How would you make this even more Groovy? Enjoy!

Related posts:

1. Get groovy for better shell scripts
2. Crush images on the command-line with Groovy
3. Griffon, meet Jython

Getting Started

You’ll need 2 tools (and Cygwin if you’re on Windows) to pull this off:

• Download and setup Groovy
• Grab ImageMagick and install it

You can do a LOT with ImageMagick. Here’s a command-line reference for it.

Compressing images the Groovy way

Here is a Groovy script I wrote for that purpose. It would be even cooler to use something like this in a Gant build:

// If directory not passed use the current directory
def dir = args?.size() ? args[0] : "."
// 70 is a fairly safe value for quality
def quality = args?.size() > 1 ? args[1] : 70

// Get an ArrayList of all PNG and JPG files
images = new File(dir).listFiles().grep(~/.*(png|jpg)$/)

for (img in images) {
    print "Crushing ${img} - size: ${img.size()}-> "
    // Compress the image
    "convert -quality ${quality} ${img} ${img}".execute().text
    println "${img.size()}"
}

Tweak this to your liking to suit your needs. You can substitute your favorite command-line image editor if you like. Groovy makes it easy!

Run it by typing this on your command-line:

groovy src/groovy/CompressImages images/ 60

What do you think? Useful? Share!

Related posts:

1. Using aliases and command-line functions for speed
2. Get groovy for better shell scripts
3. Using Groovy Categories to override operators

Getting started with command-line Groovy

Like many of the tools I advocate here, you’ll want to grab Cygwin for the best experience.

There are thorough instructions for getting Groovy running within the Groovy documentation. Basically you just download a ZIP, extract it where you want, and add a couple environment variables.

Can be installed easily on Linux or Mac:

# Homebrew
brew install groovy
# Debian-based
sudo apt-get install groovy
# With yum
sudo yum install groovy

Now you can start writing shell scripts in Groovy. Let’s write a little script to test it out:

#!/usr/bin/env groovy
println "Yay! I can finally be expressive now!"

Actually, there are a ton of ways to run Groovy, but I’m just going to focus on scripts for now.

chmod +x hello.groovy
hello.groovy

Bash vs. Groovy example

Let’s say I want to have a script that can check my friends’ last X tweets so I don’t have to leave my command-line to check twitter.

#!/bin/bash
username=xxxxxxxx
password=yyyyyyyyyy
numTweets=10

#output tweets XML
curl --basic --user $username:$password http://twitter.com/statuses/friends_timeline.xml?count=$numTweets
#Some crazy AWK goes here... your assignment ;)

I really don’t want to read my tweets in XML. Being a Java guy, I wonder if there is a way we can harness it’s power. Groovy is basically enhanced Java so I can

#!/usr/bin/env groovy

username = "xxxxxxxx"
password = "yyyyyyyyyyy"
numTweets = "10"

//If we have an argument use it
if (args && args[0].toFloat() > 0) numTweets = args[0]

//Use twitter API with cURL
output = "curl -u $username:$password http://twitter.com/statuses/friends_timeline.xml?count=$numTweets".execute().text

//Parsing XML is Amazingly easy in Groovy
tweets = new XmlSlurper().parseText(output)
tweets.status.each { tweet->
    println "${tweet.user.name}: ${tweet.text}"
}

And run it just like any shell script:

chmod +x checktweets.groovy
checktweets.groovy 15

Groovy can certainly do much more than deal with XML, it is a full-featured dynamic language with great expressiveness. It is simply satisfying to write, and you can do everything a shell script can do and more.

As an extra treat, here is a Groovy script to update your twitter status, tweet.groovy:

#!/usr/bin/env groovy

username = "xxxxxxxx"
password = "yyyyyyyyyyy"

if (args) {
    status = args[0]
    println "curl -u $username:$password -d status=\"${status}\" http://twitter.com/statuses/update.xml".execute().text
}

I personally have a /scripts directory in my home dir which I put on my path, so to run the previous script I just have to type:

tweet.groovy "Twitter is now Groovy, baby!"

Conclusion

Ok, so if you’re fairly savvy with your old-school shell scripting, I don’t expect you to switch to Groovy for simple tasks. I see 2 major cases for using it:

• You need to do complex operations on data
• You know Java better than your shell scripting

If you like Groovy and want to learn more, you might consider checking out the Groovy docs.

Tell me your thoughts!

Related posts:

1. Crush images on the command-line with Groovy
2. Using Groovy Categories to override operators
3. Introducing GroovyRTM: A Groovier way to Remember The Milk