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From Patrick Luby <>
Subject Another proposal for java.ext.dirs
Date Mon, 01 Apr 2002 21:30:13 GMT

I admit my previous method for protecting Tomcat from conflicting system 
  extensions proved to be a bit flawed. However, I still would like to 
add  some protection against these conflicts since this tends to be a 
difficult to diagnose problem for a lot of new Tomcat users. On the 
other hand, I don't think we want to prevent knowledgable users from 
using their installed extensions to support their installation.

So, here is what I propose. Note that I am in favor of checking the 
installed extensions so this proposal should be complimentary to any 
checking that might be implemented in the Tomcat code:

1. Add the following to each Java execution line in the wrapper scripts:


2. Add the following lines in setclasspath.bat and

       if [ -z "$JAVA_EXT_DIRS" ]; then
         echo "Disabling installed Java extensions. Set the"
         echo "JAVA_EXT_DIRS environment variable to the following 
         echo "to enable installed Java extensions:"
         echo "    $JAVA_HOME/jre/lib/ext"
       if not "%JAVA_EXT_DIRS%" == "" goto gotJavaExtDirs
       echo Disabling installed Java extensions. Set the
       echo JAVA_EXT_DIRS environment variable to the following value 

       echo to enable installed Java extensions:
       echo     %JAVA_HOME%\jre\lib\ext

3. If the user does not defined JAVA_EXT_DIRS (the default case), the
    java.ext.dirs property is set to "" and the above status message is
    printed. Then, if the user defines JAVA_EXT_DIRS, the existing
    behavior is enabled.

Since new Tomcat users primarily use the installed scripts, this is a 
good way to protect Tomcat without preventing other custom scripts or 
launchers from enforcing a different standard.

Does this sound like a reasonable approach? It would be nice to have 
this property setting in the class, but unfortunately, 
you must set the java.endorsed.dirs property when the JVM is started as 
it is immediately put in the JVM's bootstrap classpath.



Patrick Luby                     Email:
Sun Microsystems                         Phone: 408-276-7471
901 San Antonio Road, USCA14-303
Palo Alto, CA 94303-4900

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