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Thread: Java and ssh questions from a newbie

  1. #1
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    Default Java and ssh questions from a newbie

    Respected Java coders,
    Pardon my "noob" ness when I ask the question.
    I had done Perl Scripting earlier, where using Perl modules, the script would login to various storage devices, run a few commands, gather the outputs, filter out the unrequired sections, and email the output for monitoring alerting.
    If the script was to be run from another server, not only would it require Perl installed, but the other modules also would be required to be installed, which at times was not allowed due to security reasons.

    Java also has a similar concept of libraries / modules such as jcabi-ssh, sshj etc which allow ssh connections.

    So now suppose I write a code that does something similar as what I was doing earlier with Perl, and then save it as say my_monitoring_code.java and then:

    1) Run the
    javac my_monitoring_code.java
    command which will create a file
    my_monitoring_code.class
    and then
    2) Load my_monitoring_code.class file on another server that has Java installed and try to run it from there
    will it work? Or do I have to install the libraries / modules on the other server as well?

    Kindly let me know.

    I once again apologize if my question sounds half baked/confusing/newbie like, but would be thankful if someone could answer.

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Java and ssh questions from a newbie

    Load my_monitoring_code.class file on another server that has Java installed and try to run it from there
    The class file should execute if the javac and java programs are at the same version level or if the java program is younger than the javac program.

    Normally class files are bundled into a jar file with a manifest file so they can be executed by "opening" the jar file by clicking on it. The jar file can then be copied to other computers with compatible java commands.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java and ssh questions from a newbie

    Hi Norm,

    Thank you for the answer.

    Just for clarity, if I have the same exact version of javac and java (or younger) on the other computer, or, if I bundle it in a jar file , I don't need to install the ssh modules on the other server?

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Java and ssh questions from a newbie

    Sorry, I don't know what ssh modules are.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java and ssh questions from a newbie

    Quote Originally Posted by Norm View Post
    Sorry, I don't know what ssh modules are.
    Hi, apologies for using incorrect terminology.

    I was talking about the Java libraries such as jcabi-ssh, sshj etc which allow ssh connections.

    So my question actually was, if I have the same exact version of javac and java (or younger) on the other computer, or, if I bundle it in a jar file , I don't need to install jcabi-ssh, sshj on the other server?

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    Default Re: Java and ssh questions from a newbie

    If a java program uses a class file, that class file needs to be accessible to it when it is executed.
    If you don't understand my answer, don't ignore it, ask a question.

  7. #7
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    Default Re: Java and ssh questions from a newbie

    In case you haven't seen it, check out Oracle's Packaging Programs in JAR Files tutorial. The links "Working with Manifest Files: The Basics" -> "Adding Classes to the JAR File's Classpath" are also relevant here as they explain how the sshj or other jars can be referenced from your application's jar file.

    It might pay to start with a rather limited version of your program and play around with the process of deploying it to another computer as described in Oracle's tutorial. This might save disappointment later, and, if problems occur, you'll have something specific to ask about. It's never easy to come to grips with the nuts and bolts of a new language environment and when you throw 3rd party encryption, logging etc and build tools like gradle into the mix it's very easy to get lost. Good luck!

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