WebLogic Server : Flush the Application Cache

" On our system, what I normally do is to stop the server with the cache that needs to be flushed, then delete the tmp and cache directories of the server "

- Java Ranch Forum Post

Weblogic server maintains certain "caches" in tmp and cache folders. The caches can sometimes prove to be nuisance - especially, the tmp folder.

You can usually find the tmp folder for your application under :-

$DOMAIN_HOME/tmp/_WL_user/myApplication/

I recently ran into this issue and it gave me a couple of sleepless nights.

I had deployed my Application and started it. I then hit the URL in my browser and promptly received an error, which indicated that my cocktail of JAR files were sour and some libraries did not like the other ones.

During the next iteration of development, decided to use newer versions of a particular library. I deleted all the old libraries, provided a "gold" set of libraries ( that were certified on the vendor's website ) and then re-deployed my application.

However, I still noticed that same error. I was baffled as I was *certain* that I had removed all the old libraries.

First, I decided to investigate which JAR file was contributing the class. I retorted to good ol' Java Reflection for this - I just put this neat little piece of code in my Servlet :-

.class.getProtectionDomain().getCodeSource().getLocation();

I printed this using a simple statement and ensured that the output gets imprinted in the Server's Domain Log.

Alright, I now redeployed my application and when I invoked the Servlet, I saw this in my log file :-

$DOMAIN_HOME/servers/tmp/_WL_user/myApplication/ub48zr/war/WEB-INF/lib/myOldJARFile .jar

Bingo ! I promptly cleared the "cache" and redeployed the application. I re-invoked my Servlet and it works fine !!

I have modified my build.xml to include this minor operation - to clear the contents of the _WL_user folder and then undeploy / redeploy.

Weblogic Server : Quick EAR Deployment using WLST

" The WebLogic Scripting Tool (WLST) is a command-line scripting environment that you can use to create, manage, and monitor WebLogic Server domains. "

- Oracle Weblogic Server Manual

You can use WLST to quickly deploy an Application EAR File in a Weblogic Server.

What do you need ?

• the EAR file ( uploaded to a directory in the target WebLogic Server )
• A simple WLST script
• Credentials for the Weblogic Server ( preferrably, the weblogic user ).

How do we do it ?

• Upload your EAR file to a directory in the target Weblogic Server

/app/home/myUser/

• Write a simple WLST Script to do your work and save it as "myApp.py"
  

print '*** WEBLOGIC : START ***'

print 'connecting to admin server....'
connect( 'weblogic', 'weblogic', 't3://localhost:8001', adminServerName='AdminServer' )

print 'stopping and undeploying ....'

stopApplication('myApplication')
undeploy('myApplication')

print 'deploying....'

deploy('myApplication', '/app/home/myUser/myApplication.ear', targets='AdminServer')
startApplication('FoundationSearch')

print 'disconnecting from admin server....'
disconnect()
exit()

print '*** WEBLOGIC : STOP ***'

• Open a Terminal Window / Command Prompt
• Run the setDomainEnv.sh ( or setDomainEnv.bat ) script to set the required environment variables.
• Switch to the /common/bin directory of your Weblogic Server
• run the wlst.sh / wlst.bat script to open the Scripting Environment.
• Execute your WLST Script :-

execfile('myApp.py')

That's it ! You can now stop an application, undeloy it, deploy it & start an application with a simple script !

You need to watch out for two small things :-

• The WAR File and some of the classes / libs are "cached" under the /tmp/_WL_user/myApplication/ folder. You may need to delete them before you execute your script.
• Make sure the EAR file is available in a folder in the same node as the Server.