Documentation suggestion

Even though it's not that hard to figure out by one self, I think it  
might help some users if at least one of the example projects (or if  
the Wiki at some smart place) as built to show the pitfalls of  
java.io.Serializable and explained how one can achieve backwards  
compatibillity using local versioning of domain objects with  
Externalizable. It makes life so much easier for people such as me  
that have an evolving domain class model.

Dry-coded example:

public abstract class LegalPerson implements Serializable,  
Externalizable {

   private static final long serialVersionUID = 1l; // never change this

   private String id;
   private String name;

   @Override
   public void writeExternal(ObjectOutput objectOutput) throws  
IOException {
     objectOutput.writeInt(1); // version
     objectOutput.writeObject(id);
     objectOutput.writeObject(name);
   }

   @Override
   public void readExternal(ObjectInput objectInput) throws  
IOException, ClassNotFoundException {
     int version = objectInput.readInt();
     if (version == 1) {
       id = (String)objectInput.readObject();
       name = (String)objectInput.readObject();
     } else {
       throw new IOException("Unknown local version: " + version);
     }
   }
}

public abstract class Organization extends LegalPerson {

   private static final long serialVersionUID = 1l; // never change this

   private String organizationNumber;

   @Override
   public void writeExternal(ObjectOutput objectOutput) throws  
IOException {
     super.writeExternal(objectOutput);

     objectOutput.writeInt(1); // version
     objectOutput.writeObject(organizationNumber);
   }

   @Override
   public void readExternal(ObjectInput objectInput) throws  
IOException, ClassNotFoundException {
     super.readExternal(objectInput);

     int version = objectInput.readInt();
     if (version == 1) {
       organizationNumber = (String)objectInput.readObject();
     } else {
       throw new IOException("Unknown local version: " + version);
     }
   }
}


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