questions on J2EE

Discussion in 'Java' started by gandhi.pathik@gmail.com, Feb 9, 2007.

  1. Guest

    Hi Friends,

    I have few questions please let me know the answers. that would be
    very helpful to me.

    1). If i create 10 different request from 10 browser windows for the
    same servlet, then how we can ensure that same servlet instance is
    willing to serve all the requests?

    2).What is the difference between valueobject and plain javabean
    class?
    why valueobject is preferred over javabean class?

    3).If i write code like request.getRequestDispatcher("www.yahoo.com/
    login.jsp")? would it work or not? what will be the output?

    Thanks and Regards,
    Pathik S Gandhi
    , Feb 9, 2007
    #1
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  2. Cool Guy Guest

    Hi Pratik,

    Regarding your first questions - print this.toString() in the service
    method and then create different requests,It will give the same value
    for all request created.

    Hope it helps...

    - Sudhir

    On Feb 9, 2:49 pm, "" <>
    wrote:
    > Hi Friends,
    >
    > I have few questions please let me know the answers. that would be
    > very helpful to me.
    >
    > 1). If i create 10 different request from 10 browser windows for the
    > same servlet, then how we can ensure that same servlet instance is
    > willing to serve all the requests?
    >
    > 2).What is the difference between valueobject and plain javabean
    > class?
    > why valueobject is preferred over javabean class?
    >
    > 3).If i write code like request.getRequestDispatcher("www.yahoo.com/
    > login.jsp")? would it work or not? what will be the output?
    >
    > Thanks and Regards,
    > Pathik S Gandhi
    Cool Guy, Feb 9, 2007
    #2
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  3. Lew Guest

    > Cool Guy wrote:

    Please do not top post.

    "" wrote:
    >> 1). If i create 10 different request from 10 browser windows for the
    >> same servlet, then how we can ensure that same servlet instance is
    >> willing to serve all the requests?


    "willing to" - by writing the servlet in a thread-safe manner.

    "actually does" - I don't believe you can. Or would want to.

    You can write a servlet to implement the SingleThreadModel
    <http://java.sun.com/javaee/5/docs/tutorial/doc/Servlets5.html#wp75172>
    to force that one instance sequentially serves each request it receives, but
    not that there be only one such instance.

    From the link:
    "A web container can implement this guarantee by synchronizing access to a
    single instance of the servlet, or by maintaining a pool of web component
    instances and dispatching each new request to a free instance. This interface
    does not prevent synchronization problems that result from web components
    accessing shared resources such as static class variables or external objects.
    In addition, the Servlet 2.4 specification deprecates the SingleThreadModel
    interface."

    >> 2).What is the difference between valueobject and plain javabean
    >> class?


    "Value object' is a generic term for any object whose job is to represent a
    set of attributes - a "noun" in your object model. A "JavaBean" object is
    often a value object, and it follows a set of nomenclature and structural
    conventions put forward by the Java API. When a JavaBean is used as a value
    object, it is a particular way to implement a value object.

    >> why valueobject is preferred over javabean class?


    There is no such preference. You can use either, or both at once in the sense
    that a JavaBean in this scenario would also be a value object. I write all my
    value objects as JavaBeans.

    For many projects it is a good practice to separate the value objects
    (implemented as JavaBeans or not) from the "process objects" or "behavioral
    objects" that use the value objects. Consider EJBs, which can be entity beans
    or session beans. (An entity object is a specialization of a value object,
    also implementable as a JavaBean.)

    >> 3).If i write code like
    >> request.getRequestDispatcher("www.yahoo.com/login.jsp")?
    >> would it work or not?


    That would depend on whether there were a directory "www.yahoo.com/" relative
    to the current location within the context root, and a "login.jsp" within it
    (assuming that by "work" you mean "return a non-null RequestDispatcher object").

    >> what will be the output?


    A RequestDispatcher object or null.
    <http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequest.html#getRequestDispatcher(java.lang.String)>
    <http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/RequestDispatcher.html>

    - Lew
    Lew, Feb 9, 2007
    #3
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