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From "Joseph Morgan" <joseph.mor...@ignitesales.com>
Subject RE: Serialization
Date Mon, 04 Oct 2010 13:43:43 GMT
This has nothing to do with Tomcat.... it has to do with Java,
serialization and OO.  

What are you trying to persist because it looks like you are persisting
what amounts to be an inner class to a JSP?  Consider changing that to a
simple JavaBean not considered an inner class to the compiled JSP and
you'll be fine.  You'll never be able to cast w4a$ddm2 into w4b$ddm2 or
vice-versa, but you can cast an instance of w4a$ddm2 or w4b$ddm2 to
their common type, if they have one.  Just having the same code does not
make then the same class when compiled.

-----Original Message-----
From: Wolfgang Orthuber [mailto:orthuber@kfo-zmk.uni-kiel.de] 
Sent: Monday, October 04, 2010 8:10 AM
To: Tomcat Users List
Subject: Serialization


  Hello,

my tomcat version is 5.5.17, my question concerns serialization of 
objects, below is a code section for writing and reading an object. If I

call write immediately before read:
d5.write();
d5.read();

then all works fine, but if I use only read (on an formerly written 
file) with the same code included in another program module, I got the 
exceptions like this:
java.lang.ClassCastException: org.apache.jsp.w.w4a_jsp$1ddm2 cannot be 
cast to org.apache.jsp.w.w4b_jsp$1ddm2

in which w4a.jsp and w4b.jsp are two different modules which include the

same code for read and write. The name of the program module is stored 
in the serialized object, but the name of the program module does not 
matter, because both modules include the same code.

Do you know a simple solution which avoids the exception?

Wolfgang



The code section with read and write:


class dm5t implements Serializable {
     public ArrayList<ddm2>    v5;

     public dm5t () {  v5 = new ArrayList<ddm2> (); }

     public String topicpath(){return 
getServletContext().getRealPath("")+"/tp/";}

     public synchronized boolean write () {
         String fn=fntopics;
         boolean ok=true;
         try {
             String spath = topicpath();

             FileOutputStream    fs = new FileOutputStream (spath+fn);
             ObjectOutputStream    os = new ObjectOutputStream    (fs);
             os.writeObject (v5);
             os.close ();}
         catch (IOException e) {ok=false;} return ok;}

     public synchronized boolean    read () {
         String fn=fntopics;
         boolean ok=true;
         ArrayList<ddm2>    v5tmp=null;
         try {
             String spath = topicpath();

             FileInputStream        fs = new FileInputStream (spath+fn);
             ObjectInputStream    os = new ObjectInputStream    (fs);

             v5tmp = (ArrayList<ddm2>) os.readObject ();
             os.close ();

         } catch (IOException e) {ok=false;}
         catch (ClassNotFoundException e) {ok=false;}
         if (ok)    if (v5tmp != null) v5=v5tmp;
         return ok;}
}


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