Miles to go …

Uber Conf Day 4 (Day 3, 2, and 1) started with yet another 10 miler with fellow attendees in 1 hr 18 mins and 7:49 pace. It was slightly slower than the day before – guess physical exhaustion was setting in Here are the mile splits:

Thanks to Andy for showing how to turn on the Auto-Lap feature in Garmin 305 … really handy!

I gave a talk on how GlassFish provides a great execution environment for deploying OSGi, Java EE, and hybrid applications easily. The slides are given below:

The remainder of the day was spent in Clojure track by Stuart Halloway. Next are some basic notes for getting started with Clojure:

Why Clojure ?

• Power (hosted on jvm)
• Robustness (functional)
• Concurrency (identity, state, time)
• Abstraction (OO done right)
• Focus (lisp)

Together, these features add up to simplicity. Simplicity means

• absence of incidental complexity
• sufficient to meet your design constraints

Simplicity does not mean

• Familiarity has nothing to do with simplicity
• its not superficial, goes to the bone (e.g. only simpler syntax is just a sugar wrapper, look for the supported idioms)
• does not mean easy, its very hard to be simple

Lot of code in Clojure is not about "set" something, its about invoke a function on it.

How to get started ?

Download the latest stable release or cutting edge build. The Clojure REPL (Read-Evaluate-Print Loop) is the easiest way to run a Clojure program as shown below:

~/tools/clojure/clojure-1.1.0 >java -cp clojure.jar clojure.main
Clojure 1.1.0
user=> (print "Hello World")
Hello Worldnil
user=> ^D

OR

~/tools/clojure/jun7 >java -cp clojure.jar clojure.main
Clojure 1.2.0-master-SNAPSHOT
user=> (print "Hello World")
Hello Worldnil
user=> ^D

Notice, the first fragment shows how to run REPL using the latest stable release and the second fragment shows the same using the cutting edge build. "Ctrl+D" exits the REPL shell. Stuart mentioned that the Clojure community stays on the cutting edge build most of the times.

Alternatively, you can also clone "labrepl" from "http://github.com/relevance/labrepl" which is an environment for exploring the Clojure language. It also provides complete instructions for getting started with NetBeans/Enclojure, Eclipse/Counterclockwise, Maven, Max/Linux command line, Windows command line, IDEA/La Clojure, and Emacs.

Configuring Clojure in NetBeans using the Enclojure plugin with NetBeans 6.9 gives the following error:

but works easily with NetBeans 6.8. The IDE seem to support REPL, Java/Clojure integration, syntax highlighting, brace/paren/bracket matching, code navigation, debugger and lots of interesting features.

Here is a typical REPL getting started session with NetBeans and Enclojure:

Here are some equivalent syntax with Java:

Semantic	Java	Clojure
new	new Widget("foo")	(Widget. "foo")
Access static members	Math.PI	Math/PI
Access instance members	rnd.nextInt()	(.nextInt rnd)
Chaining access	person.getAddress().getZipCode()	(.. person getAddress getZipCode)

• "defn" is a symbol so no new syntax for adding a method.
• ^ introduces metadata for the next symbol, "greet" in this case. You can put metadata anywhere.
• "clojure.core" is the core of Clojure’s implementation
• "javadoc" knows the default JDK javadocs, can make a local copy and/or extend it
• "show" is Java reflection
• "dir", "show", "source" are promoted from community version to the bleeding edge build.
• Source is not always exposed
• [1 2 3] Call the function 1 with arguments 2 & 3.
• ‘(1 2 3) don’t evaluate it and print as is, just tick it.
• Idiomatically Clojure requires less parentheses than Java

• Every single function in Clojure is Runnable and Callable

• Java interop is simple, wrapper-free (raw), performant, complete

Compojure is a small, open source Web framework for Clojure based upon Ring (similar to Python’s WSGI and Ruby’s Rack). Otherwise Clojure apps are deployed as a JAR file.

A subsequent blog will show how to deploy a simple Clojure JAR file and a simple web app using Compojure on GlassFish.

And finally, here are my top-10 reasons (in no particular order) that I’d like to attend UberConf next year:

1. Long 90 minute sessions
2. Lots of hands-on workshops
3. Fun Run as part of the formal agenda
4. Beautiful location (Westin Westminster) with lots of running trails
5. Great food (breakfast + lunch + dinner)
6. Small attendance so intimate discussions with speakers
7. Great set of speakers
8. Rarely see session hopping
9. Pure technology, no product pitching
10. Swags are nice – bracelet-style USB stick with all the presos, 2 different tee-shirts, fancy folder and some additional goodies for speakers

See ya next year, hopefully!

Technorati: conf uberconf denver clojure compojure glassfish netbeans javaee osgi

Related posts:

1. Java EE 6, GlassFish, NetBeans, Eclipse, OSGi at Über Conf: Jun 14-17, Denver
2. Uber Conf 2010 – Day 3 Report
3. Uber Conf 2010 – Notes from Scala for Java Programmers Workshop
4. Java EE 6 & GlassFish – Spark IT 2010, Ruby Conf India 2010, Tech Days 2010
5. Über Conf Day 1 Trip Report