I've recently posted a piece on using the file-transfer adapters in Spring Integration 2.0 on the SpringSource blog. Check it out and leave a comment!

As you know from my last blog entry, I set out for Portland, OR last week to give a talk at OSCON. I arrived Wednesday nite, head south 50 miles or so to Salem, OR - where I stayed with some family. The next day - Thursday evening - I made the trek back up to Portland (in my Uncle's giant, immaculate GMC pickup truck from '89!) for my talk on using Spring Integration to connect business with their customers on Friday morning. My time in Portland - Thursday night and part of Friday afternoon - was very fun. I met Jeremy Grelle. Jeremy was also presenting that morning; his talk was on the Spring Web Stack. (If you didn't know, Jeremy works a lot on the Spring web stack - Spring Web Flow, Spring MVC, Spring BlazeDS, Spring ActionScript, etc.) A Friday at OSCON is a slow day. This particular one was only half as long as the regular conference days. So, as soon as Jeremy and I had finished our talks (they were both well received) we (two colleagues from the Shopzilla engineering group, Jeremy and I) cut out for some food and beer at Deschutes brewery not too far by train from the conference hall.

I took the chance while in Oregon to head south a little bit and visit family in Salem, Oregon. I have a lot of family up there on my dad's side. Oregon's a beautiful state, Portland a beautiful city, but Salem... Salem is a beautiful capital. There are things about Salem you'll have to see to believe. The people are nicer, the air - with Oregon being the greenest state in the union - is cleaner. I spent many a summer in Salem as a kid - making the long trek down to Bend for summer activities, enjoying the parks, the forest and - of course - the jam.

This trip felt like coming home again; I got to visit with aunt, uncle, assorted family, brother, and my niece and nephew. Time flies. I was very glad to see my brother Cary and my sister-in-law Sandy, and their family. It's been a few years, I'm afraid. His son, my nephew, is Curtis. His daughter, my neice, is Samantha.

Honestly, these sorts of stories make me feel old. Curtis was a giant! I hardly recognized him! He handily dwarfed both my brother and myself in stature and size. Whatever they feed those kids there, it's working! He has grown into quite a guy.

Curtis took my dad and I fishing on Saturday. He navigated and was the oreseman, guide, baby-sat us city-folk, handled re-baiting the lines and untangling the poles, and he still caught 5 fish (while helping ensure that dad and I each caught 4-5 fish!) It was amazing! I thought I'd seen everything. It was a catch-and-release river, so we didn't keep or eat anything we caught, but had a lot of fun nonetheless.

On Sunday, dad and I head out to Detroit Dam where we spent the early morning hours - 6 AM to 10AM - with a line hanging off the side of the dam fishing. It was as if the fish were queuing, single-file, and then jumping on our hooks.

Next comes my time with my niece, Samantha, now 16 or 17, going on 40. We spent the afternoons watching her play in a city-wide basketball tournament called Hoopla. They cordoned off certain roads in downtown Salem and had groups of all ages play in matches. First, you have to admire a town where they have the initiative to close down major streets to provide such an outdoor, summer time activity for the youths. Second, my niece was excellent! Her team was ultimately eliminated on Sunday, but it was quite a riveting few matches getting there!

I've long enjoyed Salem. It's a small city with big-city folks. I laughed so hard I hurt myself a few years ago when my aunt and I set out for something and she impatiently came to a stop at a street with THREE cars on it at rush hour. She didn't appreciate being dragged out into the rush-hour traffic - a rush hour of THREE cars. She really didn't appreciate having to stop. I poked my head out the window to see why traffic (I use the term loosely) had come to an abrupt stop, and almost fell over. There was a duck crossing!

I look forward to doing it again next year. What a good trip, with great people. And, being from Southern California, I more than appreciated the 85 degree-highs on a Summer day!

Whew! Time sure flies!

I've been working 'round the clock of late with my fellow authors Daniel Rubio and Gary Mak to wrap up the writing for Spring Recipes, 2nd Edition (more on that as it goes to press). This book's going to be second to none, folks. Spring Roo, Grails, Spring Integration, Spring Batch, Flex, REST and many (16, in fact!) other awesome chapters to bring you to the wide world of Spring 3. As a user of the Spring framework first and an author second, just trust me when I say I'd be very, very interested in buying this book if I wasn't already entitled to a free copy as an author. I digress. The book - all consuming though it is - isn't even why I'm writing this post!

Mark Fisher - lead of the Spring Integration project and all around nice guy (I'm going to throw in brilliant, as well, just in case you haven't had a chance to scour the code behind Spring Integration and come to that conclusion yourself) has been kind enough to let me contribute some adapters to the Spring Integration project - these adapters are centered around bridging communication between systems normally used by humans and automated systems. We have built support for XMPP and Twitter thus far. More's most assuredly coming, too! Looking into the crystal ball, I see ATOM and RSS playing a big part along with IRC. These adapters round out the support already provided for user-facing services like e-mail.

There's a lot of power and promise here. First, in a system with variable states, XMPP is a very promising technology because - besides being a good way for diffent entities to exchange messages (it is, after all, the backing protocol behind Google Talk and Facebook chat) - it lets you add the notion of availability to actors in your system. Imagine a game, with users joining and leaving the game, or a chat room, or a grid of grid-nodes that may be taken off-line. XMPP provides a natural way of representing availability, which is increasingly important in a system with many fluctuating agents and states.

Twitter, ATOM/RSS and others are important because they let you consume human-synthesized events. Trends, volume, etc, are all interesting metrics that can be very valuable to your business. I can see a lot of power in having a Twitter account that responds to queries or commands - in much the same way as the Smarter Child IM bot work (-s,-ed).

In some sense, these adapters are only the beginning. They let your application drink from the proverbial firehose of events, but what to do with them once you have them? Graph them? Send them to Splunk? Send them through a message broker (and, depending on the volume, which one?)? Why not send them through a complex event processing (CEP) engine like Esper using this fantastic third party Spring Integration adapter for Esper? There, you can can process and analyze these events, and synthesize more interesting, complex events.

If this all sounds interesting to you (and why wouldn't it?), you should check out OSCON next week in Portland, OR. I'll be there giving a talk called the "The Social Enterprise Service Bus." I'll be with some colleagues and friends from Shopzilla, too. If you'd like to grab a beer, ping me on Twitter (@starbuxman) and we'll see what we can do! This is my first time presenting at OSCON, so I'm looking forward to attending some of the other talks almost as much as I am about getting a chance to talk to you guys. Hope to see you there!

Hello, world! Nothing to see here, simply conducting a few tests of the software. Move along...

Often times, a message queue is used as a way to publish "events" to other services in the enterprise. The publish/subscribe architecture decouples clients from the senders and alleviates the publisher from specific knowledge of the consumers of the messages. This, plus the asynchronous nature of a message queue - the publisher does not block while clients consume the events - makes it ideal for publishing events to keep other systems aware of the state of a given system.

Now, let's establish the use case: we want to consume events in a very busy system. In our case, it's possible to receive multiple events. Or, perhaps in your system you've positioned the message queue as a way to deliver commands - "pings" - using the "command bus" pattern. It may - and quite often is - be acceptable to ignore duplicate requests in architectures like these. For example, a "command" message notifying a system that it can being processing a batch of data for the day only needs to be handled once per day, not 10 times, even if 10 different events are published. It'd be ghastly and inefficient to process the load 10x a day. What's required is some way to make message submission idempotent for certain messages - to make them indifferent to duplicate message submission.

Backstory: I've been playing with JBoss' HornetQ a lot recently. It's a very fast message queue: it recently bested ActiveMQ in the SpecJMS2007 benchmark by more than 300%!. It is able to perform these feats because it uses a native, asynchronous IO layer on Linux centered around the kernel's libaio functionality. On all other platforms, it's just gosh darned fast, regardless, but doesn't benefit from the native code acceleration.

So, imagine my surprise when I found out that HornetQ supports something it calls a Last-Value Header - a well known message header that - when the value is duplicated by other messages - causes the submitted message to override the existing message: the latest message with a duplicate header wins.

Here's how code submission to the queue looks using Spring's JmsTemplate functionality:

 
this.jmsTemplate.send (this.destination, new MessageCreator () { 
    public Message createMessage (final Session session) throws JMSException { 
        TextMessage textMessage = session.createTextMessage ( ... ); 
        textMessage.setStringProperty ("_HQ_LVQ_NAME", 
someUniqueStringThatYouSpecify);  
        return textMessage; 
    } 
}); 

So, it's often easy to find a business value that can be used to derive a semantically correct, unique key to identify duplicate events. Processing a customer's order with 3 items in the shopping cart at 12:30:30s PM? Build a key combining the 30 second window, the customer ID, the count of items, and the order ID. This provides a service-level mechanism to prevent nasty double submit issues, for example.

You need to enable this characteristic on the queue itself in the configuration files.

In HornetQ there are a few files under the $HORNETQ/config/ folder that you need to be aware of to configure HornetQ: hornrtq-jms.xml, hornetq-configuration.xml, and hornetq-users.xml. In this scenario, we need to only modify the hornetq-configuration.xml.

For a queue configured in hornetq-jms.xml

 
   <queue name="dupesQueue"> 
        <entry name="/queue/dupesQueue"/> 
        <durable>true</durable> 
    </queue> 

... you'll need to make the following changes to hornetq-configuration.xml:

 
  <address-setting match="jms.queue.dupesQueue"> 
          
<last-value-queue>true</last-value-queue> 
        </address-setting> 

Simple, right? So, go ahead, send all the messages you want - only one will remain (unless of course that message is consumed. This only guards against duplicate submissions assuming the messages haven't been delivered yet. Enjoy!

I've just posted a blog on Artima.com called SOA, 5 Years In. In it, I talk about some of the core value principals behind Thomas Erl's excellent Service Oriented Architecture: Concepts, Technology, and Design. Check it out!

I'm in my hotel room thinking about the last 3 days here at The ServerSide Java Symposium. I've had a fantastic time. I gave and/or participated in two talks: one was a talk on jBPM and Spring, the other was participation (representing Spring Integration) in a panel with Jeff Genender (representing ServiceMix) and Ross Mason (representing Mule) on ESBs. I enjoyed that process and enjoyed talking to Jeff and Ross gentlemen to the last. The 400+ people in the audience were invigorating too. Im pretty sure anybody would tell you this year was a welcome, marked improvement over previous years, especially in attendance numbers. It also heralded the introduction of a new editorial lineup, with Cameron Mckenzie taking the lead-editors position. Hes got his work cut out for him, but Im confident hes up to the task.

Rod Johnson gave a "zepo" (zero-powerpoint) Spring / Roo keynote, which was very impressive until it seemed to have failed him at the end. A post mortem revealed that the demo was fine, just a simple error. It was interesting to note that he misplaced his wedding ring and still gave a 99% performance without slides in front of 400+ people! Well done! Spring Roo seemed to garner a lot of attention from the audience and the Twitterati. Matt Raible and James Wards talk on Flex vs. GWT was fun, as expected. Jeff Genender and Keath Hesler both turned in good talks on ServiceMix. Ted Neward and Scott Davis gave their talks to great reception, as usual. Finally, my old friends Reza Rahman, Kito Mann, etc., did very well too. I missed some of the JBoss crowd (Emmanuel Bernard and Dan Allen, notably) this year, however.

It was nice meeting James Gosling, too. Can't help but feel a little in-awe. The final treat was partaking in the festivities, libations, etc., with my colleagues at Shopzilla. Tim Morrow, Senior Architect at Shopzilla, gave a very well received talk about the scale story at Shopzilla.

Hello, world! I've been utterly and completely drowned in lake-busy these last few months. Updates may be a little slow for the next month, too. I've started working as an editor for Infoq.com's Java Queue. Work is progressing apace on my next Spring book, and some exciting things are happening in my personal life pretty soon. Plus, I'm working on an opensource side-project that'll unveil hopefully pretty soon here. Anyway, check out my updates on Infoq.com if you want good old fashioned news, and on Twitter if you want commentary in 140 character chunks. Sorry I can't say more, but I will when I can! If you're going to The Server SIde Java Symposium next month (March 17-19), don't forget to say hi, and attend my sessions!

I read a very good article on breaking the crossdomain wall for Ajax requests. It's presented here, as an entry on http://www.wait-till-i.com. In it, Chris Heilmann talks about using a Yahoo service and JSON-P requests with Ajax to load any site's contents. You should most certainly read his article - it's fantastic. I post here the most salient bit (for me) since it genuinely knocked my socks off. To re-use this in your own code, copy the parts I've highlighted in bold. You can use your own version of jQuery, naturally, as the most interesting aspect is the bits inside the ajax function (which itself is pretty trivial. I created the wrapper function so that the code could be stashed away and re-used more readily). I demonstrate its use in the script fragment below that, where I load the HTML for this very site.

 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 
"http://www.w3.org/TR/html4/strict.dtd"> 
<html> 
<head> 
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
  <title> ZOMG! </title> 
  <link rel="stylesheet" href="styles.css" type="text/css"> 
</head> 
<body> 
 
<script src="http://code.jquery.com/jquery-latest.pack.js"></script> 
<script language="javascript"> 
function ajax ( url, cb){ 
 var yqlUrl =  "http://query.yahooapis.com/v1/public/yql?"+ 
            "q=select%20*%20from%20html%20where%20url%3D%22"+ 
              encodeURIComponent (url)+ 
            "%22&format=xml'&callback=?" ; 
 $.getJSON ( yqlUrl,  cb ); 
} 
</script> 
 
<script language="javascript"> 
$ (document).ready (function (){ 
 ajax ( 'http://www.joshlong.com', function (data){ 
  alert ( data.results[0] +'' ) ; 
 }); 
}); 
</script> 
</body> 
</html> 

I can't tell you how powerful overcoming the leap-before-looking temptation is when building a system. Have an object model? Model it using UML or ERD. Have a workflow? Draw a workflow diagram (an activity diagram). Have a webflow? Draw a webflow diagram (looks like a state diagram, or in more sophisticated scenarios, like an activity diagram). Have a site map? Map the site using a site planning tool like Denim. All of these tools facilitate VISUAL feedback. They are cognitive, high level disciplines, and for good reason! Your mind interprets things visually differently than it does when coding from the left brain - it is able to "see" associations between related concepts when it's fed ideas through feedback that ends up in the right brain.

I've mentioned this before, I think, but check out Neal Ford's On the Lam From The Software Police for more.

Even if you don't check it out, invest in trying the modeling tools associated with the task you're attempting to solve. Even if you feel - after giving the technology a REALLY good-faith effort - that you've gained nothing, I'm willing to bet your product will still be more "consistent" than if you had developed it from scatch, unable to see the big picture.