JNDI name duplication problem chez WebSphere

Yesterday a colleague and I have faced a subtle problem deploying a suite of enterprise applications on WebSphere Application Server - version 6.1.

The problem manifested itself with a marshalling error when a webapp called a service exposed as an EJB in the same enterprise application: this was very annoying due to two main aspects:

1. there was no duplication, between webapp and EJB module, fot the classes involved in the call
2. the issue seemed to occur randomly: not for all calls (and never for some), not always for the same call (apparently depending to application restart)

After a few hours of stop-and-start-and-read-the-log nightmare, we discovered that at the root of the problem was a JNDI name duplication between EJBs published by two different applications of the suite: these applications are based on the same infrastructural framework, and the framework published some framework services using a fixed JNDI name. This was clearly an error in suite packaging, but... WebSphere did not report in any way this name collision, deployed without errors nor warnings both the applications, and the duplicated JNDI name was associated with an implementation of the service or with the other, depending to starting order of the apps. So:

1. the marshalling problem appeared when the webapp from an EAR called the service published by the other application
2. the issue occurred only for the EJB with the duplicated name, not for the others; and coccurred or did not depending to the starting order

The solution was quite simple: changing the JNDI name of  one of the twins services.
But... why the application server did not give any error when deploying an EJB using an already-in-use JNDI name, as do for example JBoss and BEA Weblogic application servers?

Definitely something to remember!

How-to find a class in a JAR directory using shell scripting

The biggest problems in J2EE applications deployment  come often from classloader hierarchies and potential overlapping between server-provided and application-specific libraries. So, searching classes through collection of JARs is oftwen the main activity in order to identifiy and fix classloader issues.

This is surely a tedious and repetitive task: so, here's a shell script you can use to automate JAR collection traversing and tar command's output analysis to search a pattern, which is provided as script parameter.

Credits: Thanks to sirowain for parameter check and return code related contributions.

#!/bin/bash
# Commonly available under GPL 3 license
# Copyleft Pietro Martinelli - javapeanuts.blogspot.com
if [ -z $1 ]
then
        echo "Usage: $0 <pattern>"
        echo "tar xf's output will be tested against provided <pattern> in order\
          to select matching JARs"
        exit 1
else
        jarsFound=""
        for file in $(find . -name "*.jar"); do
                echo "Processing file ${file} ..."
                out=$(jar tf ${file} | grep ${1})
                if [ "${out}" != "" ]
                then
                        echo "  Found '${1}' in JAR file ${file}"
                        jarsFound="${jarsFound} ${file}"
                fi
        done
        echo "${jarsFound}"
        
        echo ""
        echo "Search result:"
        echo "" 
        
        if [ "${jarsFound}" != "" ]
        then
                echo "${1} found in"
                for file in ${jarsFound}
                do
                        echo "- ${file}"
                done
        else
                echo "${1} not found"
        fi
        exit 0
fi

This script is available on github.com:

https://github.com/pietrom/javapeanuts-shell-utils/blob/master/find-jar.sh

How to clean-up JBoss temporary directories using bash scripting

Repetitive and annoying file system tasks are the natural field of automation through shell scripting - so, here's a script  that can be used to clean up temporary directories created by JBoss Application Server.

You can provide as parameter the name of the node that you want clean up - if launched without parameters, the script cleans up temporary directories in each node under current installation.

Tested on JBoss 4.0.5.GA and JBoss 5.1.0.GA installations.

#!/bin/bash

# Commonly available under GPL 3 license

# Copyleft Pietro Martinelli - javapeanuts.blogspot.com

function cleanTmpDir {
        echo "  Cleaning ${1}/${2}"
        rm -rf "${1}/${2}"

}

function cleanNode {
        echo "Cleaning \"${1}\" jboss node"
        for tmpDir in data log tmp work
        do
                cleanTmpDir ${1} ${tmpDir}
        done
}


if [ $# -eq 0 ]
then
        for dir in $(find server -maxdepth 1 -mindepth 1 -type d)
        do
                cleanNode ${dir}
        done
else
        if [ -e "server/${1}" ]
        then
                cleanNode "server/${1}"
        else
                echo "${1} is not a subdir of server dir"
        fi
fi

Updated: this script is now available on bitbucket.org:
https://bitbucket.org/thecleancoder/javapeanuts-shell-utils/src