Hello,
for anybody who has been running into this exception when trying to
execute
JSPs:
javax.servlet.ServletException: sun/tools/javac/Main
Heres the solution:
tools.jar is not recognized when it's in classpath
thus it must be copied to
{tomcat_root}/common/lib
and/or
{tomcat_root}/server/lib
The Tomcat startup scripts start up Tomcat in such a way that the existing
CLASSPATH is ignored completely.
They do this by creating another environment variable called _CLASSPATH, which
contains the default CLASSPATH variable's values, if any. The startup scripts
then proceed to assemble together a CLASSPATH which is used to start and run
Tomcat. This CLASSPATH contains only those Jars that are present in the Tomcat
sub-directory.
Once this tomcat specific CLASSPATH is created, it is used to startup Tomcat.
Now, the ony other places from where jars/clases might be loaded is the
%JAVA_HOME%/jre/lib/ext folder. The extensions Classloader, which is one of the
three Classloaders that work when the JVM comes up, loads all classes and Jars
that are present in this folder.
If you next use the supplied shutdown scripts, then the default CLASSPATH is
restored, using the values fromthe _CLASSPATH environment variable.
>My opinion:
>I've been chasing down this problem for three days now, and all I could
>find
>in the respective mailing list databases was: put tools.jar in the
>classpath. But that didn't work. Eventually I found the solution
>mentioned
>above - as I wrote - after three days.
If the JAVA_HOME environment variable is correctly defined, then the startup
scripts correctly construct a Tomcat specific CLASSPATH environment varialbe
that includes %JAVA_HOME%/lib/tools.jar. If you have such an environment
variable, and yet you have to copy tools.jar to a Tomcat subfolder, then please
check the value of this environment variable. For e.g. I have installed JDK
1.3.1 at e:\jdk1.3.1 on my WinNT 4.0 system, and the value of the JAVA_HOME
environment variable on my system is e:\jdk1.3.1\ (with the trailing
backslash). This constructs the correct CLASPATH for me, which includes the
tools.jar.
>Ever since I started working with java and that was four years ago, the
>classpath has been a problem in java. I would expect that in the
>meantime
>the directory structures would be sufficiently standardized and thus
>make
>_any_ classpath settings unnecassary. Once JAVA_HOME and/or JAVA_PATH
>are
>set the environment should be defined.
>But that's not the case. To make things worse, sometimes like in this
>case,
>the classpath settings are ignored. Who would have expected that
>tools.jar
>needs to be _copied_ to some other location? I wouldn't.
While it might be frustrating to those who do not know that their carefully
constructed CLASSPATH is actually ignored by the startup scripts, this can be a
book actually. Quite a few Tomcat users have big unmanageable CLASSPATHs and
jars scattered all over the place, and supporting such setups via this
mailinglist can be a real nightmare.
>Because I wouldn't
>expect _any_ developer of java and escecially java server applications
>to
>propose a configuration, where system jars are located in more than one
>location. Thus maintenance of the system becomes a nightmare when a
>system
>update is due.
>I just hate when that happens.
The firm that I work for is soon going to deliver a some 6 web apps, all of
which will be running on Tomcat 4.0.1
Because of the way Tomcat's startup scripts work, we are not particularly
concerned with other jars etc that might be added to the system on a later
date. And then what if the customer were to change the CLASSPATH variable's
values ? The way the startup scripts work right now, we are at least sure that
if there are any new Jar files, we know where to place them. And if there are
any conflicts in the future, either there's some foreign jar files in our
Tomcat folder, or in %JAVA_HOME%/jre/lib/ext And no more worries about the
CLASSPATH being changed, etc.
If you'd indeed like the Tomcat startup scripts to refer to your system jars,
then you could customize the file catalina.bat (catalina.sh for unix users) The
place to do your customization is in the section titled
"rem ----- Set Up The Runtime Classpath
----------------------------------------"
You'll see here that the tools.jar is referred by the line
set CP=%CATALINA_HOME%\bin\bootstrap.jar;%JAVA_HOME%\lib\tools.jar
If you'd like to support additional System libraries, say something product
called XYZ which is available at e:\XYZ\lib\xyz.jar,
then you could add a line like this,
set CP=%CP%;e:\XYZ\lib\xyz.jar
>Sincerely
>Michael Kastner
Sriram
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