-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Wolfgang,
(Marking off-topic because this is a Java/JSP issue and not Tomcat-related. See below for responses.) On 10/4/2010 9:10 AM, Wolfgang Orthuber wrote: > my tomcat version is 5.5.17 Upgrade. > 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 That funny error message occurs because you are trying to write one class object and read it in as another class object. You should read-up on serialization for more information: http://java.sun.com/developer/technicalArticles/Programming/serialization/ > in which w4a.jsp and w4b.jsp are two different modules which include the > same code for read and write. That means that they are different classes, and are therefore incompatible. You should use a class defined in a .java file and not in a .jsp file. Your other option is to provide customized serialization that can read and write data without relying on Java's serialization mechanism (which mandates that the classes be the same in order to work). > 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. No, the fact that they are the same code is irrelevant. Only the data and the metadata are relevant, and the metadata doesn't match between these two distinct classes. > Do you know a simple solution which avoids the exception? Use the same class for both reading and writing. > The code section with read and write: Is this inside a .jsp? If so, create a separate class. What are you doing putting Java code into a JSP file, anyway? More comments below... > class dm5t implements Serializable { > public ArrayList<ddm2> v5; > > public dm5t () { v5 = new ArrayList<ddm2> (); } > > public String topicpath(){return > getServletContext().getRealPath("")+"/tp/";} Note that getRealPath isn't guaranteed to return a non-null value: a filesystem isn't guaranteed by the servlet specification, but temporary storage is guaranteed using the "temp dir". See the servlet spec for details. > public synchronized boolean write () { Why synchronized? > 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;} > } Why do you catch exceptions and return error codes? You like C-style return codes instead of the elegance and clarity of exceptions? - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkyqD2AACgkQ9CaO5/Lv0PCg4gCgni4RiDBJpyernjkWo48ENrCL Pz4AoLu28l17XZwK22+sGW7AVQZcM19/ =B03Y -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
