Re: Java server won't run after reboot

From: Bob Smith (bob_at_netprt.com)
Date: 05/31/04

  • Next message: Larry Brown: "RE: Setting RH9 for static IP" 
    Date: Mon, 31 May 2004 11:19:45 -0600 (MDT)
To: "General Red Hat Linux discussion list" <redhat-list@redhat.com>

    Oops, on the last example, set the classpath for a jar as follows:

    export CLASSPATH=<pathtojar>/MyHelloWorld.jar
    e.g. Using /opt/myapp/lib as <pathtoyourclasslocation>
    export CLASSPATH=/opt/myapp/lib/MyHelloWorld.jar

    HTH,

    -Bob

    > Working with classpaths in Java isn't too hard, but there are some rules
    > to follow.
    >
    > 1. Simplest scenario: Executing in the same directory, and there are no
    > package definitions in your source code. Example: HelloWorld, no package
    > definition. Execute from that directory, no classpath definition needed.
    > eg.
    >
    > Class HelloWorld { ... }
    >
    > 2. Next simplest: You compile without packages defined:
    > using the same directory for source and compiled classes, or if you
    > compiled classes to a different directory:
    >
    > export CLASSPATH=<pathtoyourclasslocation>
    > example directory: /opt/myapp/lib/
    > then
    > export CLASSPATH=/opt/myapp/lib/
    > and call it:
    > java HelloWorld
    >
    >
    > 3. Adding a package definition to your source code, and there is a
    > definite source code hierachy. Using the package example below:
    >
    > package project.testjava;
    > Class HelloWorld { ... }
    >
    > Your directory structure should look like this:
    > <pathtoyoursourcelocation>/project/testjava/HelloWorld.java
    >
    > Assuming that you compile your code in the same directory and deposit the
    > class files there, then set your classpath as follows:
    >
    > export CLASSPATH=<pathtoyoursourcelocation>
    > e.g. Using /opt/myapp/source/ as <pathtoyoursourcelocation>:
    > ex. export CLASSPATH=/opt/myapp/source/
    >
    > and call the application as follows:
    >
    > java project.testjava.HelloWorld
    >
    > --------------------------------------------
    >
    > If you compile to a different location, then your directory structure will
    > look like this after a compilation:
    >
    > <pathtoyoursourcelocation>/project/testjava/HelloWorld.java
    > <pathtoyourclasslocation>/project/testjava/HelloWorld.class
    >
    > Then set the classpath as follows:
    > export CLASSPATH=<pathtoyourclasslocation>
    > e.g. Using /opt/myapp/lib as <pathtoyourclasslocation>
    > export CLASSPATH=/opt/myapp/lib
    >
    > and call the application as follows:
    >
    > java project.testjava.HelloWorld
    >
    > 3. You've compiled to a jarfile, e.g. MyHelloWorld.jar
    > export CLASSPATH=<pathtojar>/MyHelloWorld.jar
    > e.g. Using /opt/myapp/lib as <pathtoyourclasslocation>
    > export CLASSPATH=/opt/myapp/lib
    >
    > and call as follows:
    > java project.testjava.HelloWorld
    >
    >
    > -Bob
    >
    >> On Saturday 29 May 2004 05:44 pm, you wrote:
    >>> That didn't work. I still get the NoClassDefFoundError. Any other
    >>> ideas?
    >>
    >> You're right !! it doesn't work. I just try this myself, and whenever I
    >> try to
    >> execute from outside the directory where the java files is located, I
    >> got
    >> the
    >> same error. I thought I've seen this and what I suggested was the
    >> solution,
    >> obviously not ! (Now it should be obvious that I am not a java developer
    >> myself, I just play with it sometime)
    >>
    >> After some searching myself, I only have this solution:
    >>
    >> If for example, my java program is in
    >> ~/project/testjava/helloworld.java,
    >> I
    >> can put in helloworld.java:
    >>
    >> package project.testjava;
    >> <rest of the src code>
    >>
    >> then I need to go to ~, and compile it from there:
    >> javac project/testjava/helloworld.java
    >>
    >> and running it from there would work tpp:
    >> java project/testjava/helloworld
    >>
    >> The problems with the solution: First, I can't find a way so that I can
    >> use
    >> absolute path during compile and running (which is probably what you
    >> want
    >> in
    >> your case, since you're going to put the command in rc.local). So what I
    >> want
    >> is something so that I can say:
    >>
    >> javac /home/<username>/project/testjava/helloworld.java
    >> java /home/<username>/project/testjava/helloworld
    >>
    >> when I tried, the solution does not work. I can't also figure out what
    >> to
    >> put
    >> in after the "package" keyword in the source code to make the absolute
    >> path
    >> work.
    >>
    >> Secondly, the source code is dependent on what directory you want to
    >> compile
    >> and run the java program from. Unless I am missing something, that is
    >> just
    >> plain stupid !! Source code of a program should never be dependent on
    >> where
    >> the program is running from.
    >>
    >> So that's it. I am kinda stuck right now too. I don't know if that would
    >> help
    >> you, but if you find the real solution, please let me know, cause right
    >> now
    >> it bugs the hell out of me too ! (BTW, I have a task of writing some
    >> java
    >> program in the near future, so this would be good to know).
    >>
    >> I know this is going OT, but if anyone else on the list know a solution,
    >> please help.
    >>
    >> RDB
    >>
    >>
    >>> On Sat, 2004-05-29 at 11:59, Reuben D. Budiardja wrote:
    >>> > On Saturday 29 May 2004 12:16 pm, Michael Sullivan wrote:
    >> <snip>I wrote a java server that I want to start every time
    >>> > > my server PC restarts. I created a /usr/local/classes directory
    >>> and
    >>> > > copied Server.class and the support classes it uses there. Id cd'd
    >>> to
    >>> > > /usr/local/classes and issued a java Server from there and it works
    >>> > > fine, but if I issue a java /usr/local/classes/Server from anywhere
    >>> > > outside the /usr/local/classes directory it tells me
    >>> > >
    >>> > > Exception in thread "main" java.lang.NoClassDefFoundError:
    >>> > > /usr/local/classes/Server
    >> <snip>
    >>> > Try the following:
    >>> > set the environment variable CLASSPATH to /usr/local/classes so that
    >>> Java
    >>> > knows where to find your classes. Asumming you're using bash:
    >>> > $> export CLASSPATH=$CLASSPATH:/usr/local/classes
    >>> >
    >>
    >>
    >> --
    >> Reuben D. Budiardja
    >> Department of Physics and Astronomy
    >> The University of Tennessee, Knoxville, TN
    >> ---------------------------------------------------------
    >> "To be a nemesis, you have to actively try to destroy
    >> something, don't you? Really, I'm not out to destroy
    >> Microsoft. That will just be a completely unintentional
    >> side effect."
    >> - Linus Torvalds -
    >>
    >>
    >> --
    >> redhat-list mailing list
    >> unsubscribe mailto:redhat-list-request@redhat.com?subject=unsubscribe
    >> https://www.redhat.com/mailman/listinfo/redhat-list
    >>
    >
    >
    > --
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