Question

I need serialize objects into String and deserialize.

I readed sugestion on stackoverflow and make this code:

class Data implements Serializable {
int x = 5;
int y = 3;   
}

public class Test {
public static void main(String[] args) {

    Data data = new Data();

    String out;

    try {
        // zapis
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);

        oos.writeObject(data);

        out = new String(baos.toByteArray());
        System.out.println(out);

        // odczyt.==========================================

        ByteArrayInputStream bais = new ByteArrayInputStream(out.getBytes());

        ObjectInputStream ois = new ObjectInputStream(bais);

        Data d = (Data) ois.readObject();

        System.out.println("d.x = " + d.x);
        System.out.println("d.y = " + d.y);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

}

}

but I get error:

java.io.StreamCorruptedException: invalid stream header: EFBFBDEF
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:801)
at java.io.ObjectInputStream.<init>(ObjectInputStream.java:298)
at p.Test.main(Test.java:37)

Why?
I expected:
d.x = 5
d.y = 3

how to do in good way?
Ah. I don’t want to write this object in file. I have to have it in string format.

Answer 1

Use
ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray()); instead of
ByteArrayInputStream bais = new ByteArrayInputStream(out.getBytes());, since the String conversion corrupts the data (because of the encoding).

If you really need to store the result in a String, you need a safe way to store arbitrary bytes in a String. One way of doing that is to us Base64-encoding.

A totally different approach would have been to not use the standard Java serialization for this class, but create your own Data to/from String converter.