[jdom-interest] Serialization Trouble through Inheritance

[Oliver Ruebenacker]

     Hello,

  Rolf, it shouldn't be necessary to add these methods.

  Björn, can you check the import statement for Element?

     Take care
     Oliver

On Thu, Aug 9, 2012 at 10:37 AM, Rolf Lear <jdom at tuis.net> wrote:
>
> Hi Björn
>
> I don't have my 'JDOM Laptop' with me at the moment, so I can't easily
> reproduce your problem, but, I suspect this is just an issue of
> implementing your own read/write object methods.
>
> What happens if you add the following methods to your 'MyElement' class? I
> believe this should fix things..... try it... :-)
>
>
>
>         /**
>          * Serialize out the MyElement.
>          *
>          * @serialData
>          * The Stream protocol is:
>          * <ol>
>          *   <li>Write the super Element class out...
>          * </ol>
>          *
>          * @param out where to write the Element to.
>          * @throws IOException if there is a writing problem.
>          */
>         private void writeObject(final ObjectOutputStream out) throws IOException
> {
>                 out.defaultWriteObject();
>         }
>
>         /**
>          * Read a MyElement off the ObjectInputStream.
>          *
>          * @see #writeObject(ObjectOutputStream)
>          * @param in where to read the Element from.
>          * @throws IOException if there is a reading problem.
>          * @throws ClassNotFoundException when a class cannot be found
>          */
>         private void readObject(final ObjectInputStream in)
>                         throws IOException, ClassNotFoundException {
>                 in.defaultReadObject();
>         }
>
>
> Rolf
>
>
>
> On Thu, 09 Aug 2012 16:08:48 +0200, Björn Buchner
> <b.buchner at isys-software.de> wrote:
>> Hi Folks,
>>
>> I am using the JDOM 2.0.2 release and experienced some trouble when it
>> comes to serialization.
>>
>> De-/serializing an Element object through the standard
>> ObjectOutput/InputStream is no problem. Trouble starts when I try to
>> deserialize an object of a class that inherits from Element.
>>
>> It always ends with a InvalidClassException: no valid constructor.
>> Normally this indicates that JRE is missing a public default
>> constructor, but as you can see in the example below the subclass
>> has a default constructor.
>>
>> Thanks in advance for your help
>>
>> Example code:
>>
>> public class MyElement extends Element {
>>
>>      private static final long serialVersionUID = -4220756491425652053L;
>>
>>      public MyElement() {
>>          super();
>>      }
>>
>>
>>      public static void main(String ... args) throws IOException,
>> ClassNotFoundException {
>>         ByteArrayOutputStream buffer = new ByteArrayOutputStream();
>>         ObjectOutputStream outStream = new ObjectOutputStream(buffer);
>>
>>         MyElement element = new MyElement();
>>
>>         outStream.writeObject(element);
>>         outStream.flush();
>>         ObjectInputStream inStream = new ObjectInputStream(new
>> ByteArrayInputStream(buffer.toByteArray()));
>>         element = (MyElement)inStream.readObject();
>>      }
>> }
>>
>> Result:
>>
>> Exception in thread "main" java.io.InvalidClassException:
>> <packageremoved>; no valid constructor
>>      at
>>
> java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:147)
>>      at
>> java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:755)
>>      at
>>
> java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1751)
>>      at
> java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
>>      at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
>>      at <packageremoved>.main(MyElement.java:29)
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