Desktop application and web application Linking...

Discussion in 'Java' started by Robin Saini, Jul 1, 2013.

  1. Robin Saini

    Robin Saini Guest

    Hello everyone,
    Can I create an object of Desktop application class into a web application class? as I am facing a problem "java.lang.ClassNotFoundException" doing same.
     
    Robin Saini, Jul 1, 2013
    #1
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  2. On 01.07.2013 07:19, Robin Saini wrote:
    > Hello everyone, Can I create an object of Desktop application class
    > into a web application class?


    What is "create an object ... into" supposed to mean? Are you talking
    about casting one to the other? Are you trying to create the latter and
    pass the former to the constructor? What classes are we talking about
    here at all?

    > as I am facing a problem
    > "java.lang.ClassNotFoundException" doing same.


    What exactly are you doing?

    robert


    --
    remember.guy do |as, often| as.you_can - without end
    http://blog.rubybestpractices.com/
     
    Robert Klemme, Jul 1, 2013
    #2
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  3. Robin Saini

    Robin Saini Guest

    Thanks for Reply.
    I have a method that creates a bar chart of some hard-code data(in array). I can call this method in Main method and it shows me the chart in new window(desktop window not web). I want to do the same thing on click of a button of jsp page. So I created a servlet(and jsp as well) and call that class(which creates chart) but My servlet is not able to create object of that class. It shows an exception of class not found.

    please guide me.
    --Thanks
    Robin
     
    Robin Saini, Jul 1, 2013
    #3
  4. Robin Saini

    Lew Guest

    Robin Saini wrote:
    > I have a method that creates a bar chart of some hard-code data(in array).. I can call this method in Main method and it shows me the chart in new window(desktop window not web). I want to do the same thing on click of a button of jsp page. So I created a servlet(and jsp as well) and call that class(which creates chart) but My servlet is not able to create object of that class. It shows an exception of class not found.
    >
    > please guide me.


    The more evidence you can examine, the better. It sounds like you have a build
    problem, that is to say, you need to examine how you build your web app.

    You haven't given us much evidence, just a vague description, but the one
    piece of hard evidence you did provide, "java.lang.ClassNotFoundException",
    is indicative.

    This hints that you did not build a WAR, and further that you are attempting
    to invoke Java code directly from a JSP, which is a big no-no in Java Web
    apps. That's even if you are using correct syntax, let alone modern syntax.

    So the bad news is, absent contrary evidence, you have a lot of mistakes
    in your application, some fatal and some more slowly so.

    Which is normal, especially as one is learning. And then forever after that..

    The tricky part is figuring out what you did wrong, especially when you are
    new to a platform. This means asking the right questions, first of yourself
    and then of others.

    Here's what you need to learn:
    - Using Expression Language (EL) and JSP tags
    to eliminate the appearance of Java code in your JSP pages.
    Most of the tags you need should exist already. I can't recall ever actually
    needing to write a custom tag. Good. It would have been more trouble than
    it's worth.

    Logic, OTOH, I can write in Java. Then you use EL to push and pull values
    to the display.

    Logic, of the model kind, does not belong in the presentation layer, the JSP.
    Look up "Model-View-Controller (MVC)".

    - How to build a Java package, properly.
    This begins with thoroughly understanding the JAR file, which is where your
    "java.lang.ClassNotFoundException" would have been found.

    Then you can thoroughly understand the WAR file, which is the Java Web app
    supersized JAR file, which in turn is Java's megawatt ZIP file.

    Then you can read how to deploy a WAR to Tomcat or other favorite app server.

    - The standard build process for Java Web apps.

    Your exception stems from not putting the class in the right place, asking
    for it from the wrong place, and not having thoroughly read the instructions
    yet. That last becomes a lifelong habit. So many times I find the answers to
    questions I have in fundamental documentation (i.e., tutorials) that I've
    actually read. Many times. And needed to read again.

    Besides, a lot of documentation is fun, like "What Every Computer ScientistShould Know About Floating-Point Arithmetic".

    --
    Lew
     
    Lew, Jul 1, 2013
    #4
  5. Robin Saini

    Arne Vajhøj Guest

    On 7/1/2013 3:58 AM, Robin Saini wrote:
    > Thanks for Reply. I have a method that creates a bar chart of some
    > hard-code data(in array). I can call this method in Main method and
    > it shows me the chart in new window(desktop window not web). I want
    > to do the same thing on click of a button of jsp page. So I created a
    > servlet(and jsp as well) and call that class(which creates chart) but
    > My servlet is not able to create object of that class. It shows an
    > exception of class not found.


    Can we get the full exception text and the full stack trace and
    some code snippets around the location of the problem?

    That may give us an indication of where the problem exist.

    Arne
     
    Arne Vajhøj, Jul 5, 2013
    #5
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