Casting Classes in jsp

Question

[att1.html]
          

Answer 1

Use byte array output stream to serialize into. Ask it for the byte array.
          You now have an object (the byte array) that contains the serialized form of
          the object that you serialized.
          Pick a name to store that byte[] under. I assume if you encountered a class
          cast exception that you already have a name picked. Store the byte[]
          instead of the original object. Put it in using setAttribute.
          Now where you take the object out with getAttribute, you have to instead
          instantiate a byte array input stream and an object input stream on top of
          that and bring that object back to life.
          I suggest encapsulating all of this so you can get rid of it if deploying to
          other servers or when WL fixes the class loading. It's only about 20 lines
          of code total.
          Cameron Purdy
          http://www.tangosol.com
          "Suchak Jani" <[email protected]> wrote in message
          news:[email protected]...
          Also there is one more thing i wanted to ask,
          How do we put the objects in the session after serializing them ?
          Thanks and Regards
          Suchak Jani
          Cameron Purdy wrote:
          It might imply that WL was trying to build the necessary .class files in one
          of its tmp directories; that is all that comes to mind. I am very glad that
          you were able to solve it though!
          Cameron Purdy
          http://www.tangosol.com
          "Suchak Jani" <[email protected]> wrote in message
          news:[email protected]...
          Hi Cameron,
          You are right in saying that the soultions are :-
          To avoid this problem, you can serialize the objects that you store (instead
          of the object themselves). You can also take the classes out of the
          WAR/servletclasses directory and add them to the base classpath (not
          advised, but can work). You can also use "built in" classes (like
          java.lang.whatever) instead of your own, since they are loaded by the system
          class loader. I'd suggest searching the JSP and Servlet newsgroups here for
          "class loader" and "classloader". You'll find plenty of problems and some
          solutions.
          I do not know and maybe i have not researched enough how to put the
          objects after serializing them in the session where i get the hashtable
          from.
          But just to tell you how we solved the dreaded classcast or at least how
          we think we solved it is the follows :-
          We had .java files also in the classpath with the .class files. We deleted
          the
          .java files and it worked ??
          Does that make ay sense to you ??
          Thanks and Regards
          Suchak Jani
          PS : Thank you so much for your timely help in this matter .
          Cameron Purdy
          http://www.tangosol.com
          "Suchak Jani" <[email protected]> wrote in message
          news:[email protected]...
          Why do java objects need to be casted ?
          Why do objects not know who they are ???
          I mean what the point of having collection classes
          like Vectors, Hashtables store everything as an Object. WHY ???
          I would be very happy to know the answer.
          Coming from a smalltalk background and knowing that collection
          classes are so important to devloping large applications in OO,
          it is difficult to see why every object must be casted.
          I was doing this casting to get objects from collection classes for last
          several months ,though not appreciating it very much.
          Today one of my JSP fails with a ClassCastException.
          The scenario is this :-
          I have an object stored in a HashTable , let us call this "X".
          In the JSP i am getting the object from the hashtable and
          casting it like this :-
          X y = (X) hashtable.get(key);
          I get a ClassCastException.
          Now if i do like this: -
          System.out.println("Object :" +hashtable.get(key) )
          X y = (X) hashtable.get(key);
          It gives me this:-
          Object : X@234e
          ClassCastException
          Now , i am at a complete loss to understand why ??
          I would great appreciate if anyone has any answers.
          Thnaks and Regards
          Suchak Jani