asked on

Serialize object to a byte array

Hi,

Can someone show me how to serialize a simple class to a byte array? Something like:

class Test implements Serializable {
String str = "hello";
}

void main()
{
Test t = new Test();
ByteArray b = new ByteArray();
t.toBytearray(b);

// later on just recreate the object from the byte array
Test t2 = new Test();
t2.fromByteArray(b);
}

Thanks

ASKER CERTIFIED SOLUTION

Bart Cremers

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drazen_nikolic

The proposed solution is OK.
Anyhow, last year I have found one interesting post with the class enabling to easy serialize/deserialize JAVA objects (actually the list of objects).

Check next URL (seek for the last post):
http://forum.java.sun.com/thread.jspa?threadID=5226234&tstart=0

You have a very good example there. Hope this helps.

DJ_AM_Juicebox

ASKER

Hmm not having any luck - I get an IOException as soon as I try to write. Here's the sample I had put together, pretty much exactly like yours, I must be missing something:

public class Main
{
public class Test1 implements Serializable {
public static final long serialVersionUID = 0;
String m_str = "hello";
public Test1() {}
}

public static void main(String[] args)
{
Main m = new Main();
m.test();
}

public void test()
{
// Serialize first.
Test1 t1 = new Test1();
System.out.println("Test1: " + t1.toString());

ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(t1);

Yeah right there it throws an IOException, on writeObject().... any idea what I'm missing?

Thanks

Bart Cremers

Could you provide more info on the error message?

DJ_AM_Juicebox

ASKER

It is pretty useless to me, it just says:

"Main"

I use it like:

try {
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(t1);
}
catch (IOException e) {
System.out.println(e.getMessage());
}

Bart Cremers

Seeing the full stack trace might help out in finding the problem.

DJ_AM_Juicebox

ASKER

How do you do a full stack trace? I just get:

[Ljava.lang.StackTraceElement;@7bb290

after calling:

System.out.println(e.getStackTrace());

Bart Cremers

Just do e.printStackTrace();

DJ_AM_Juicebox

ASKER

ok here it is:

java.io.NotSerializableException: Main
      at java.io.ObjectOutputStream.writeObject0(Unknown Source)
      at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source)
      at java.io.ObjectOutputStream.writeSerialData(Unknown Source)
      at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source)
      at java.io.ObjectOutputStream.writeObject0(Unknown Source)
      at java.io.ObjectOutputStream.writeObject(Unknown Source)
      at Main.test(Main.java:40)
      at Main.main(Main.java:26)

DJ_AM_Juicebox

ASKER

it appears it can't work because my definition of Test1 is inside another class - so only top level classes can be serialized I guess. How annoying!

Bart Cremers

You could make the Test1 class static or make Main serializable as well. The Main class will be an anonymous member of the subclass, so it needs to be serializable as well.