How to binary (de)serialize object into/form string?

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.

Why exactly do you want to store a binary representation in a String in the first place ? Why not just keep it as a byte array or something ?... — Costi Ciudatu
– Costi Ciudatu, Commented Nov 26, 2012 at 16:03
@CostiCiudatu beacuse I have to write a method which store objects into sqlite database but part in sqlite is not depend on me. And there is text column. Now I have xml serialization but it is slow. I need fast way. — LunaVulpo
– LunaVulpo, Commented Nov 27, 2012 at 7:04
Did you check if SQLite supports something like BLOB for storing raw bytes ? — Costi Ciudatu
– Costi Ciudatu, Commented Nov 27, 2012 at 7:09

Aleksander Blomskøld · Accepted Answer · 2012-11-26 15:58:51Z

11

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.

edited Nov 26, 2012 at 15:58

answered Nov 26, 2012 at 15:51

Aleksander Blomskøld

18.6k10 gold badges79 silver badges82 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Peter Lawrey Over a year ago

+1 don't forget to close the stream as well as its buffered. ;)

LunaVulpo Over a year ago

Base64 slowed this problem. :)

Ralph Ritoch Over a year ago

Thanks, I should have known this was an encoding issue. In my case I needed to use org.apache.tomcat.util.codec.binary.Base64 with Base64.encodeBase64String to create the string and Base64.decodeBase64 to decode it.

ngrislain · Accepted Answer · 2014-01-09 22:37:38Z

11

It is not entirely true to say that conversion to string corrupts the data. Conversion to "UTF-8" does because it is not bijective (some characters are 2 bytes but not all 2 bytes sequences are allowed as character sequences), while "ISO-8859-1" is bijective (1 character of a String is a byte and vice-versa).

Base64 encoding is not very space-efficient compared to this.

This is why I would recommend:

/**
 * Serialize any object
 * @param obj
 * @return
 */
public static String serialize(Object obj) {
    try {
        ByteArrayOutputStream bo = new ByteArrayOutputStream();
        ObjectOutputStream so = new ObjectOutputStream(bo);
        so.writeObject(obj);
        so.flush();
        // This encoding induces a bijection between byte[] and String (unlike UTF-8)
        return bo.toString("ISO-8859-1");
    } catch (Exception e) {
        e.printStackTrace();
    }
}
/**
 * Deserialize any object
 * @param str
 * @param cls
 * @return
 */
public static <T> T deserialize(String str, Class<T> cls) {
    // deserialize the object
    try {
        // This encoding induces a bijection between byte[] and String (unlike UTF-8)
        byte b[] = str.getBytes("ISO-8859-1"); 
        ByteArrayInputStream bi = new ByteArrayInputStream(b);
        ObjectInputStream si = new ObjectInputStream(bi);
        return cls.cast(si.readObject());
    } catch (Exception e) {
        e.printStackTrace();
    }
}

answered Jan 9, 2014 at 22:37

ngrislain

1,12213 silver badges19 bronze badges

1 Comment

Ron Klein Over a year ago

How can you be sure that the binary representation can be converted to String? For instance, how can the String terminator character (usually \0 in C) be converted to a valid character inside the String? The answer is, you can't. For that reason we should convert the byte array to a safe textual representation, such as Base64.

Collectives™ on Stack Overflow

How to binary (de)serialize object into/form string?

2 Answers 2

3 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related