Question

There is a class I want to serialize, and it implements Serializable, but one of the objects it contains does not implement Serializable.

Is there a way to modify the class at runtime to make it implement the Serializable interface so I can serialize it? I can’t change it at compile time because its a third party library.

Maybe I would have to use some sort of bytecode writer or something?

EDIT: Both the containing class and contained class are in the 3rd party library so I don’t think i can mark something as transient. The containing class is marked as serializable, but it contains an object that is not.

I’m fine with writing a custom serialization method for the class, not sure how I would do this though, would I have to use reflection to get the values of the private variables?

Answer 1

Reading the javadoc for Serializable, I see:

Classes that require special handling
during the serialization and
deserialization process must implement
special methods with these exact
signatures:

private void writeObject(java.io.ObjectOutputStream out)
     throws IOException
 private void readObject(java.io.ObjectInputStream in)
     throws IOException, ClassNotFoundException;
 private void readObjectNoData() 
     throws ObjectStreamException;

which you could use to manually serialize the uncooperative fields. You could look into using ASM, but it seems hard to believe that it is a maintainable solution.