Shailesh’s Blog

I gave a talk on “Using LCDS to Power Live REAs” at SilvaFug South and showed Zephyr as an example of this. I briefly discussed what forced us to go down this route followed by a quick 30 min demo of the product. Explained general philosophy behind LCDS, things to keep in mind while designing applications based on LCDS, issues and misconceptions around LCDS and how we got around those issues. Here are the presentation slides.

One fine day my smooth running tomcat 5.5.23 started giving this error. Most surprising thing was that nothing had change in my setup or the application which could result such a drastic error.

2009-04-13 11:18:54,665 ERROR [main] [/flex].listenerStart(3715) | Error configuring application listener of class com.thed.server.event.DataListener
java.lang.NoClassDefFoundError: javax/servlet/ServletContextListener
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:675)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:280)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1274)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3712)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4216)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:760)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:740)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:626)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:553)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:488)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:736)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:448)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
at org.apache.catalina.startup.Catalina.start(Catalina.java:552)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)


The issue turned out to be permission issue of the working folder where I started tomcat from. I realized this when I tried to check version of java and got following error.

Error occurred during initialization of VM
java.lang.Error: Properties init: Could not determine current working directory.
Abort trap

Also discussed in this thread - http://forums.sun.com/thread.jspa?threadID=560395

Any case, I shutdown and started tomcat from a different folder and every thing was honky dory again.

Amazon recently announced cloudFront, a content delivery service. Like all other amazon service, this service is also very simple to implement with pay as you go pricing. It made sense for us to move our website static contents and downloadable files to cloudfront. It took us less then half a day from signing up for the service to move everything over to Amazon. Now, all the static resource for www.getzephyr.com is served up from CloudFront.

CloudFront doesn’t yet support media streaming but its in their roadmap. I can’t wait to move ZephyrTV files over to CloudFront.

Its barely been two weeks since we formally announced ZaaS (Zephyr as a Service) and got selected as one of the 6 finalists in AWS Startup Challenge. It would be tough for a enterprise software to compete against consumer software and not even a fair one. But hey, if it was easy, any body could have done it. Some of the sites talking about it:

• AWS Start up challenge
• TechCrunch
• Venture beat
• NY Times

Its not very common to come across a need to install php on a J2EE server. For the same reason, there is not enough documentation written around this. It took me a while to figure out all the pieces. Hope this is helpful.
Environment
Tomcat : 5.5.23
OS: Fedora
PHP: 5.2.6
Assumptions
tomcat is already installed
Mysql is already installed

Steps

1. Download and deploy PHP Java Bridge from http://php-java-bridge.sourceforge.net (just copy the war file to /webapps)
2. Recompile PHP (with various option) that are not there in the binary that come with the above bridge

If you are using log4j [Simplest, easiest and most common way of doing it]
a. log4j.xml
Add following entry:

b. log4j.properties
Create a logger category
log4j.logger.org.hibernate.SQL=DEBUG

If you just want these on the console (quick n dirty), then set the hibernate.show_sql to true in your sessionFactory configuration.

More Info

I am attending 360Flex in San Jose. Day one wasn’t great in terms of new stuff to learn except few things. I attended following sessions

This morning as usual, I was browsing google finance and suddenly I noticed this.

Does any thing look wrong there. Well, yeah. How is Dow, despite of + growth, showing up in red. And that provoked one of my all time pet peeves - JavaScript. Decades of innovation and evolution and still large amount of web developers still putting up with the inherent pains of the language. Still not feeling the pain?
Why should you not use java script
1. Its painful to write
2. Even more painful to debug
3. Each browser treats it differently
4. Error prone
5. Poor testablity
6. Hard to read and understand somebody’s code.

Flex/Actionscript addresses all the above plus
1. Fun to write
2. Better maintainability
3. Works seamlessly with JavaScript and variety of browsers.
4. Applicability of OOPS concepts and Design patterns
5. Better XML, JSON and other data format editing capabilities
6. Asynchronous by nature.
7. Memory management and bench marking

And hence, UI of our test management tool, to a great extent, is written in Flex/Actionscript while utilizing strengths of java script also where ever necessary.

I am by far not a gadget freak. But I do go out once in a while to check out whats going on. Recently, I had a need to look at the gadget API. While going thro’ Google’s Gadget Tools documentation, I noticed some of the documentation is outdated. One that I was concerned with, was link to add developer gadget. Lazy enough, I googled it and found that other people also noticed that the link has been removed. After a bit of struggling, it turned out, the gadget is still there, just the link is not.

Here is what I ended up doing as a work around. Type following url in your browser (replace $YOUR_TAB_NAME with your the tab that you want to add that gadget).

http://www.google.com/ig/directory?root=/ig&igtab=$YOUR_TAB_NAME$&dpos=top&url=developer.xml

Press enter, you will get following screen

Add the gadget, and thats it.