Tue Apr 07 22:52:51 +0000 2009

… and applied the Unicode guide to date format patterns to come up with the format:

E MMM dd k:mm:ss Z yyyy

Once I had the pattern, it was as simple as setting it onto a NSDateFormatter instance and using its API.

NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
[inputFormatter setDateFormat:@"E MMM dd k:mm:ss Z yyyy"];
NSDate *date = [inputFormatter dateFromString:twitterTimestamp];
NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
[outputFormatter setDateFormat:@"M/d @ HH:mm"];
NSString *formattedDate = [outputFormatter stringFromDate:date];

Hope this helps someone save a bit of time.

SEVERE:  Error listnerStart

After some GoogleFu, I found a thread on the SpringSource forums with a great tip on where to debug the application to find the issue. Dropping a break point in the ContextLoaderListener where you see:

this.contextLoader.initWebApplicationContext(event.getServletContext());

Start your application using Tomcat’s admin manager and your break point will catch this line. Allow one Step Return and view the ‘t’ variable in your runtime variables (upper right-hand corner). You’ll see the offending exception.

This listener class is acting as the bootstrap to start up the Spring container, so when this call fires, it rips through all the XML and builds your beans, etc. This is why applications die before they start … any exception thrown during the bootstrap or bean creation phases will kill the application.

Thanks to SpringSource forum user “adam_jh”!

As for my side projects, my iPhone application was nearly completed when I read about Blizzard sending cease & desist letters to all active iPhone application authors who have done any work on their game-related property. So much for tackling that niche community…oh well, it was a good learning experience.

On the web front, I spent some time during my paternity leave working on some design tweaks for my MLB boxscore website (Boxscore Junkie). Still have a lot of ideas for it but I am also working on new iPhone application ideas so my time will be split once again.

1. It’s here!  Java is now officially supported on GAE.  Exciting news and I’m ready to finally spend the time learning the datastore now.  Learn more from the source.
2. Standford is posting their iPhone Development course free online via iTunes.  Follow along at the course website.

There’s never enough time in the day, is there?  So many things to learn…

“The technologies of greatest interest to I.B.M. are Java and Solaris, and those are notably not hardware technologies,” said David M. Smith, an analyst at Gartner.

As a Java engineer, there are a couple of things that hit me right away.  What would this mean for the NetBeans and Eclipse?  They are completely separate IDEs with various pluses and minuses.  Personally, I like Eclipse for almost all web development thanks to open source plug-ins for PHP, Python, HTML/CSS/JavaScript.  Rich-Client Platform development is also a value-add Eclipse brings to the table as many companies are building RCP suites with reuseable components that operate both online and offline.  Where NetBeans excels (in my short experience with the product) is in their GUI editor for Swing development.  Any developer who has written AWT/Swing code can probably attest to the convenience of the drag-and-drop palettes opposed to prgrammatically aligning your GridBagLayout containter within a FlowLayout JFrame…but I digress.

Secondly, what will happen to Glassfish in the face of WebSphere?  Would IBM try to consolidate?  Would they let the Sun developers and researchers continue their work with the free application server?

As an infrastructure engineer, you need to ask the long-term question of why would IBM support Solaris when it is heavily into other flavors of Unix?  Currently it is competitive business between the two entities Sun and IBM.  But if they were to be owned by the same parent, would it be fiscally prudent to continue to develop both paths?  I can’t imagine it would be, which would reduce the rate at which we grow these technologies (given that competition is the greatest motivation for innovation).  Granted, there’s a lot of customers out there who will be impacted and a lot of contracts on the books for years to come that would prevent IBM from potentially shutting down the Solaris side of things.  Or maybe IBM moves their Linux resources into the Solaris space?  Interesting to ponder.

I’ve probably raised a lot of fantasy questions here, but it’s worth pondering.  The NYTimes article talks about IBM/Sun building a Java front against Microsoft…well…that would certainly be a formidable company for sure and would most likely ensure that Java stays at the forefront of software technologies for the next decade or two at least.

After getting used to way the deskop and applications interact, it’s pretty smooth to get around.  I really love the Command+Space Spotlight shortcut…Windows needs this feature in their next OS.  Finder is pretty solid, though I’ve yet to figure out why sometimes I can see files in Finder and sometimes I can’t, or, sometimes I’ll see them on the file system using Terminal but still can’t find them in Spotlight or Finder.  Strange … I must be doing something wrong.

I’ve made it about halfway through Cocoa Programming for Mac OS X and half to say I am really enjoying it.  It’s definitely got the feel of the RCP dabbling I did in Eclipse but it feels like there is some stronger third party at work.

I also got Apache and PHP configured and running (comes with!), and installed MySQL.  In addition to LAMP, I installed the Google Application Engine and copied over my applications from my Vista machine.  I really like the GAE launcher that is installed…a nice GUI interface to launch applications from, look at logs, and manage multiple apps / port numbers running off the app server script.

Long story short, I am very impressed with the Mac and I haven’t even gotten into iMovie or iPhoto.  Next on my plate is to finish my first iPhone application and to setup my Java development environment here on Leopard.  Oh, and I need to figure out if I want a local SVN or try out this GIT version control system…to be continued!

<%    StringBuffer buf1 = new StringBuffer("javascript:");
        buf1.append(portletResponse.encodeNamespace("setValues")+ "(${myIndex});");
        buf1.append(JSPScriptHelper.generateFormSubmissionJS(portletResponse, "mainForm", "flow_details", "myPage","N"));
%>
<someTag:someAction id="customBehaviour_setValues" refId="submit${myIndex}" event="click" jsFunction="<%=buf1.toString()%>" />

That JavaScript was intended to create a form submission action and inside of JSPScriptHelper was code that called portletResponse.createURI() and appended the resulting URI to the function. This URI was unqiue, based on the state of the portlet (different for each render, in this case) which was then appended to the rest of the JavaScript including the expression language tag ${myIndex}.

The output looked something like this:

javascript:PC_7_E1HDLKG100G7902NLUVANH1045_setValues(${myIndex});javascript:setMandatoryCheckInfo('PC_7_E1HDLKG100G7902NLUVANH1045_mainForm','myPage','N');PC_7_E1HDLKG100G7902NLUVANH1045_submitAction(document.PC_7_E1HDLKG100G7902NLUVANH1045_mainForm,'/1/myportal/!ut/p/c1/04_SB8K8xLLM9MSSzPy8xBz9CP0os3hXQw8XH293QwP_MH83AyM_jwDTsEBTINccKB-JW97diCTdBj5uFkB5b0MPizBHI3dLQwK6_Tzyc1P1I_WjzJHMcDe3BKryCQ1z9PMwNDAx1Y_MSU1PTK7UL8gNjSjPd1QEAEgoflQ!/dl2/d1/L0lJSklna21DU1EhIS9JRGpBQUV5QUJFUkNKRXFnL1lGTkExTkk1MC01Rjg5dyEvN19FMUhETEtHMTAwRzc5MDJOTFVWQU5IMTA0NS91eGJUNDMzL3NhLmZsb3dfZGV0YWlscw!!/#7_E1HDLKG100G7902NLUVANH1045');

Everything after myportal is the unique URI and after writing some debug code within the ELEvaluator which printing each expression it cached, we could see that this was the cause of the leak. There were two ways to fix this issue. First, we could re-write our JSF component to not accept a JavaScript function in this manner and simply write the function to the page without going through the component. However if the component is a necessary step in processing, then the second option is to re-write ELEvaluator to use an LRU cache. This may hurt performance though depending on the frequency of the page and number of users, given that you are no longer caching the expression representation.

I spoke with one of the JSTL caretakers, Henri Yandell, and he told me that he’s look at Q1 for a patch release with a fix for this issue, in either version 1.1.3 and/or 2.0, yet to be determined. In the meantime, avoid using dynamic expressions in your JSF / custim tag arguments.

Syntax error on token "}", delete this token
Syntax error on token "catch", Identifier expected
Syntax error, insert "Finally" to complete TryStatement

I actually found out what my problem was through the Eclipse Web Tools usergroup. The issue for me was the use of the Spring form custom tag library. If you self-close the tag…

<form:errors path="*" />

…then you get the goofy JSP validation error. If you close the tag as if there was body content…

<form:errors path="*"></form:errors>

Then the error goes away. I need to follow-up with a bug for the Ganymede team.

/**
 * @version svn:$Id$
 */

After the commit, the file did not update as expected. I did some further digging and found a forum post that discussed another option where you set the property on the file. So I experimented with that using the Team > Set Property … command in eclipse on a single file. Setting the property name to svn:keywords and value to Id. I made a simple change to my file and committed it again. Voila! It worked.

The last step was to apply this keyword to all of my files…and preferably not manually. The answer was to go to the root of my project and set the property there, noting to check the Set property recursively check box. If I want to add more keywords later on, I can by going to the root, modifying the svn:keywords property by adding other keywords (refer to the manual again) separated by a single space.

This increased our load from 10 pages per second to over 100 … our first indicator that something was wrong. We saw a corresponding spike in CPU from 8% to over 90% as the single JVM system tried to handle this new load. The application seized and thread dumps uncovered an interesting side effect. Forty-eight of the 65 allocated web container threads were waiting to lock on the synchronized method getEvaluatorByName() in ExpressionEvaluatorManager, a class provided by the Java Standard Tag Library. Here’s a sample from the thread dump:

"WebContainer : 49" daemon prio=5 tid=0x04a86830 nid=0xa1 waiting for monitor entry [0x59a7d000..0x59a7fc28]
    at org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.getEvaluatorByName(Unknown Source)
    - waiting to lock <0xeb30d958> (a java.lang.Class)
    at org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager.evaluate(Unknown Source)

Looking at the source code, you can see the Evaluator retrieval and lazy instantiation of the Evaluator cache is done within this synchronized method. The intent was to prevent duplicate Evaluators from entering the cache, but the side effect of this approach is that every “get” is synchronized.

Synchronization Blocking – standard-1.0.3.jar

public static synchronized ExpressionEvaluator getEvaluatorByName(String name) throws JspException {
		try {
			Object oEvaluator = nameMap.get(name);
			if (oEvaluator == null) {
				ExpressionEvaluator e = (ExpressionEvaluator)
				Class.forName(name).newInstance();
				nameMap.put(name, e);
				return (e);
			} else
				return ((ExpressionEvaluator) oEvaluator);
		} catch (ClassCastException ex) {
			// just to display a better error message
			throw new JspException("invalid ExpressionEvaluator: " +
			ex.getMessage(), ex);
		} catch (ClassNotFoundException ex) {
			throw new JspException("couldn't find ExpressionEvaluator: " +
			ex.getMessage(), ex);
		} catch (IllegalAccessException ex) {
			throw new JspException("couldn't access ExpressionEvaluator: " +
			ex.getMessage(), ex);
		} catch (InstantiationException ex) {
			throw new JspException("couldn't instantiate ExpressionEvaluator: " + ex.getMessage(), ex);
		}
	}

A better approach would be to move the synchronization “lower” in the chain by removing the lock at the method level and creating a static block around the lazy instantiation of the cache. The project owners recognized this as a bottleneck in 1.0.6 and released the following revised version of the same method.

Fixed – standard-1.0.6.jar

public static ExpressionEvaluator getEvaluatorByName(String name) throws JspException {
	Object oEvaluator = nameMap.get(name);
	if (oEvaluator != null) {
		return ((ExpressionEvaluator) oEvaluator);
	}
	try {
		synchronized (nameMap) {
			oEvaluator = nameMap.get(name);
			if (oEvaluator != null) {
				return ((ExpressionEvaluator) oEvaluator);
			}
			ExpressionEvaluator e = (ExpressionEvaluator)
			Class.forName(name).newInstance();
			nameMap.put(name, e);
			return (e);
		}
	} catch (ClassCastException ex) {
		// just to display a better error message
		throw new JspException("invalid ExpressionEvaluator: " + ex.getMessage(), ex);
	} catch (ClassNotFoundException ex) {
		throw new JspException("couldn't find ExpressionEvaluator: " + ex.getMessage(), ex);
	} catch (IllegalAccessException ex) {
		throw new JspException("couldn't access ExpressionEvaluator: " + ex.getMessage(), ex);
	} catch (InstantiationException ex) {
		throw new JspException("couldn't instantiate ExpressionEvaluator: " + ex.getMessage(), ex);
	}
}

This code solution reduces contention to almost nothing, as there is only one Evaluator defined (hard-coded, acutally) in the out-of-the-box version of the standard tag libraries. In conclusion, it’s always a good idea to absorb updates in the thirty party libraries you are using! Most Java applications won’t see this issue unless they have extremely heavy traffic or are using automated load or procedures to churn through their site.