I posted a few days ago about finding which JAR file contains a class file – something I often want to do.  My friend Chris Johnson promptly posted a better version here with caching – thanks Chris!

Chris said I inspired him to finish his script 🙂 and in return he has inspired me to improve it further.  As I often work with JAR files in a development environment, and often a lot of them, the search can take a while, so the caching is great.  But – those files can change over time, so I need the cache to be kept up to date.

Here is an updated version of Chris’ version that will update the cache if a JAR file is newer than the cache:

#!/bin/sh
TARGET="$1"

CACHEDIR=~/.jarfindcache

# prevent people from hitting Ctrl-C and breaking our cache
trap 'echo "Control-C disabled."' 2

if [ ! -d $CACHEDIR ]; then
    mkdir  $CACHEDIR
fi

for JARFILE in `find $PWD -name "*jar"`
do
  CACHEFILE=$CACHEDIR$JARFILE

  if [ ! -s $CACHEFILE ]; then
      mkdir -p `dirname $CACHEFILE`
      nohup jar tvf $JARFILE > $CACHEFILE
  # if the jar file has been updated, cache it again
  elif [ $JARFILE -nt $CACHEFILE ]; then
      nohup jar tvf $JARFILE > $CACHEFILE
  fi

  grep $TARGET $CACHEFILE > /dev/null
  if [ $? == 0 ]
  then
    echo "$TARGET is in $JARFILE"
  fi
done

P.S.  If you are running this on Ubuntu (or Debian), like me, you better make that first line a bit more explicit:

#!/bin/bash

Enjoy!