Java serializing object with ObjectOutputStream works once , tried reset() on both sides

Question

I am using this static class as a way to serialize objects into strings before sending / using them in various ways. However the objects being serialized only seem to be serialized correctly once. A variable that starts at 20 and increments every update only gets to 21 even though if I print it right before its serialized , the value is correct ( somewhere around 1500 ).

Before you answer , note that I am using reset() and writeUnshared(). I tried pretty much everything I could find online and nothing seems to work.

public class InformationInterface {

static ObjectInputStream ois;
static ObjectOutputStream oos;
static ByteArrayOutputStream baos;

public static Object fromString( String s ) throws IOException ,
        ClassNotFoundException {
    byte [] data = Base64.getDecoder().decode( s );
    ois = new ObjectInputStream(
            new ByteArrayInputStream(  data ) );
    Object o  = ois.readUnshared();
    ois.close();
    return o;
}

public static  String toString( Serializable o ) throws IOException {
    if(baos!=null){
        baos.flush();
    }
    baos = new ByteArrayOutputStream();
    baos.reset();
    oos = new ObjectOutputStream( baos );
    oos.reset();
    oos.writeUnshared(o);
    oos.flush();
    oos.close();
    return Base64.getEncoder().encodeToString(baos.toByteArray());
}

}

I have read many posts here stating that ObjectInputStream keeps a reference of sent objects ( Even though im creating a new one every time and only keeping a reference in between serializations ) using writeUnshared() or reset() works at sending multiple objects but I cant seem to get it to work on my part.

I dont understand why this isnt working. Im not even sending multiple objects simultaneously and simply want a way to serialize the same object throughout the lifetime of my server. However , the received serialized based64 String does not change at all after the first update is received.

Note that I tried multiple other ways to do it , including sticking a direct try/catch block creating an entirely new objectoutputstream and calling reset right where I would usually call these static functions. I also tried using ObjectOutput and ObjectInput and got the same result.

Everyone seems to have solved their problem using reset() , well this isnt my case. Could I be doing something wrong somewhere else in my code ? Since I read the data before its serialized and can confirm that it should be in fact a new object right before its serialized I doubt the problem is very far.

Edit , Just tried a different way using apacheutils and I get the exact same results. Here is the new code with the output :

public static Object fromString( String s ) throws IOException ,
        ClassNotFoundException {
    return convertFromBytes(Base64.getDecoder().decode(s));
}
private static byte[] convertToBytes(Serializable object) throws IOException {
    ClientInformation client = (ClientInformation)object;
    System.out.println(client.hp);
    return SerializationUtils.serialize(object);
}
private static Object convertFromBytes(byte[] bytes) throws IOException, ClassNotFoundException {
    return SerializationUtils.deserialize(bytes);
}
public static  String toString( Serializable o ) throws IOException {
    String s = Base64.getEncoder().encodeToString(convertToBytes(o));
    System.out.println(s);
    return s;
}


794
rO0ABXNyACBjb20ucjMuZW5kZ2FtZS5DbGllbnRJbmZvcm1hdGlvbj8t7NEouSNIAgAISQACaHBTAAdzbmFrZWlkSQAIc3Bkc2NhbGVMAANhYmN0ABJMamF2YS9sYW5nL1N0cmluZztMAAJpcHEAfgABTAAEbmFtZXEAfgABTAAIcG9zaXRpb250AB9MY29tL2JhZGxvZ2ljL2dkeC9tYXRoL1ZlY3RvcjI7TAAFc3BlZWRxAH4AAnhwAAADGgGkAAAAAXB0ABAvMTI3LjAuMC4xOjQ1Mzk0dAAHYXMzMmRkZHNyAB1jb20uYmFkbG9naWMuZ2R4Lm1hdGguVmVjdG9yMgyu1b5sQZuzAgACRgABeEYAAXl4cAAAAAAAAAAAc3EAfgAGPczMzQAAAAA=
795
rO0ABXNyACBjb20ucjMuZW5kZ2FtZS5DbGllbnRJbmZvcm1hdGlvbj8t7NEouSNIAgAISQACaHBTAAdzbmFrZWlkSQAIc3Bkc2NhbGVMAANhYmN0ABJMamF2YS9sYW5nL1N0cmluZztMAAJpcHEAfgABTAAEbmFtZXEAfgABTAAIcG9zaXRpb250AB9MY29tL2JhZGxvZ2ljL2dkeC9tYXRoL1ZlY3RvcjI7TAAFc3BlZWRxAH4AAnhwAAADGwGkAAAAAXB0ABAvMTI3LjAuMC4xOjQ1Mzk0dAAHYXMzMmRkZHNyAB1jb20uYmFkbG9naWMuZ2R4Lm1hdGguVmVjdG9yMgyu1b5sQZuzAgACRgABeEYAAXl4cAAAAAAAAAAAc3EAfgAGPczMzQAAAAA=
796
rO0ABXNyACBjb20ucjMuZW5kZ2FtZS5DbGllbnRJbmZvcm1hdGlvbj8t7NEouSNIAgAISQACaHBTAAdzbmFrZWlkSQAIc3Bkc2NhbGVMAANhYmN0ABJMamF2YS9sYW5nL1N0cmluZztMAAJpcHEAfgABTAAEbmFtZXEAfgABTAAIcG9zaXRpb250AB9MY29tL2JhZGxvZ2ljL2dkeC9tYXRoL1ZlY3RvcjI7TAAFc3BlZWRxAH4AAnhwAAADHAGkAAAAAXB0ABAvMTI3LjAuMC4xOjQ1Mzk0dAAHYXMzMmRkZHNyAB1jb20uYmFkbG9naWMuZ2R4Lm1hdGguVmVjdG9yMgyu1b5sQZuzAgACRgABeEYAAXl4cAAAAAAAAAAAc3EAfgAGPczMzQAAAAA=
797
rO0ABXNyACBjb20ucjMuZW5kZ2FtZS5DbGllbnRJbmZvcm1hdGlvbj8t7NEouSNIAgAISQACaHBTAAdzbmFrZWlkSQAIc3Bkc2NhbGVMAANhYmN0ABJMamF2YS9sYW5nL1N0cmluZztMAAJpcHEAfgABTAAEbmFtZXEAfgABTAAIcG9zaXRpb250AB9MY29tL2JhZGxvZ2ljL2dkeC9tYXRoL1ZlY3RvcjI7TAAFc3BlZWRxAH4AAnhwAAADHQGkAAAAAXB0ABAvMTI3LjAuMC4xOjQ1Mzk0dAAHYXMzMmRkZHNyAB1jb20uYmFkbG9naWMuZ2R4Lm1hdGguVmVjdG9yMgyu1b5sQZuzAgACRgABeEYAAXl4cAAAAAAAAAAAc3EAfgAGPczMzQAAAAA=

As you can see , the serialized string is identical.

Answer 1

This is something you should do not me FYI.

From context of code I did:

public static void main(String[] args) throws IOException {
    ClientInformation ci = new ClientInformation();
    //      System.out.println(toString(ci));
    toString(ci);
    ci.hp = 3;
    toString(ci);
    //      System.out.println(toString(ci));
}

@SuppressWarnings("serial")
private static class ClientInformation implements Serializable {
    public int hp = 2;
}

I ran it from IDE using your code and this is the result:

2
rO0ABXNyADduZXRjcmF3bGVyLmZhY3Rvcmllcy5BcHBsaWNhbnRGYWN0b3J5JENsaWVudEluZm9ybWF0aW9uu7p3ca7TTqkCAAFJAAJocHhwAAAAAg==
3
rO0ABXNyADduZXRjcmF3bGVyLmZhY3Rvcmllcy5BcHBsaWNhbnRGYWN0b3J5JENsaWVudEluZm9ybWF0aW9uu7p3ca7TTqkCAAFJAAJocHhwAAAAAw==

Strings DOES NOT MATCH . The problem is not here.