ObjectInputStream & ObjectStreamClass problems (5)

[Wu, Gansha]

Consider the following snippet in ObjectInputStream:

public final Object readObject () throws ClassNotFoundException, IOException
{
     ... ...
     switch (marker){
     case TC_CLASSDESC:{
           ... ...
           setBlockDataMode (true); 
           osc.setClass (resolveClass (osc));
           setBlockDataMode (false); 
     }
     ... ...
     }
     ... ...
}

When we encounter class description, we must resolve it and add (Class, 
ObjectStreamClass) 
entry into ObjectStreamClass cache(ObjectStreamClass.classLookupTable), but in
ObjectStreamClass.java:
void setClass (Class clazz)
{
    this.clazz = clazz;
}
Nothing is done with classLookupTable. The consequence is: when next time the 
ObjectStreamClass for a specific Class is lookuped, nothing will be found and a 
new ObjectStreamClass for the Class is created. See the following in 
ObjectStreamClass.java:

public static ObjectStreamClass lookup (Class cl)
  {
    if (cl == null)
      return null;
    if (! (Serializable.class).isAssignableFrom (cl))
      return null;

    ObjectStreamClass osc = (ObjectStreamClass)classLookupTable.get (cl);
    if (osc != null)
      return osc;
    else
    {
      osc = new ObjectStreamClass (cl);   <-----
      classLookupTable.put (cl, osc);
      return osc;
    }
  }

"new ObjectStreamClass (cl);" is called to create the ObjectStreamClass for 
Class cl. Note: this time 
ObjectStreamClass constructor will generate all the information about the Class 
cl according to local 
class definition but not the class description from the stream. e.g, it will 
get fields information by 
Field.getDeclaredFields(), but not fields information from stream.
So I think we might modify setClass like the following:

void setClass (Class clazz)
{
    this.clazz = clazz;
+   ObjectStreamClass osc = (ObjectStreamClass)classLookupTable.get (clazz);
+   if (osc == null)
+     classLookupTable.put (clazz, this);
}