Question

I am trying to test a program and for that I need to access ReadExternal function but I am getting StreamCorrupted exception on ObjectInputStream.
I know I need to use the object written by WriteObject but dont know how to do it…

ObjectOutputStream out=new ObjectOutputStream(new ByteArrayOutputStream());
    out.writeObject(ss3); 
    ss3.writeExternal(out);
    try{
         ByteInputStream bi=new ByteInputStream();
         bi.setBuf(bb);
         out.write(bb);
         ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(bb));
         String s1=(String) in.readObject();
        }
        catch(Exception e){
            e.printStackTrace();
        }

Answer 1

Apparently, you are trying to write the same object twice to the output stream:

out.writeObject(ss3); 
ss3.writeExternal(out); // <-- Remove this!

The second write makes wrong use of the writeExternal() method, which should never be called explicitly but will be called by the ObjectOutputStream.

And: out.write(bb); tries to write the content of bb to the ObjectOutputStream. That’s probably not what you want.

Try it like this:

// Create a buffer for the data generated:
ByteArrayOutputStream bos = new ByteArrayOutputStream();

ObjectOutputStream out=new ObjectOutputStream( bos );

out.writeObject(ss3);

// This makes sure the stream is written completely ('flushed'):
out.close();

// Retrieve the raw data written through the ObjectOutputStream:
byte[] data = bos.toByteArray();

// Wrap the raw data in an ObjectInputStream to read from:
ByteArrayInputStream bis = new ByteArrayInputStream( data );
ObjectInputStream in = new ObjectInputStream( bis );

// Read object(s) re-created from the raw data:
SomeClass obj = (SomeClass) in.readObject();

assert obj.equals( ss3 ); // optional ;-)