Convert an Object to ByteArray

[Kunal Aher]

Hi,
I plan to write an application where the Object is stored to some secondary storage. Can anyone suggest how we can convert an Object to a array of Bytes , so that I can store the Objects ?
Has anyone come across a similar problem , and if yes , what was the solution that was adopted ?
All ideas welcome .

[Michael Morris]

Hi Kunal,
Why not just Serialize the Object onto an ObjectOutputStream? You can write your objects to a file like this:

        ObjectOutputStream oos = new ObjectOutputStream(
                                 new FileOutputStream(
                                 new File("myData.dat")));
        SomeSerializable obj1 = new SomeSerializable();
        SomeSerializable obj2 = new SomeSerializable();
        oos.writeObject(obj1);
        oos.writeObject(obj2);
        ...
        oos.close();

You can then later read them back like this:

        ObjectInputStream ois = new ObjectInputStream(
                                new FileInputStream(
                                new File("myData.dat")));
        SomeSerializable obj1 = (SomeSerializable) ois.readObject();
        SomeSerializable obj2 = (SomeSerializable) ois.readObject();
        ...
        ois.close();

Any object that you write to the File must implement the Serializable interface which has no methods and for that reason is called a tagging interface. Members declared transient will not be written to the File and there are some other issues that you may want to read about in the javadocs on ObjectInputStream and ObjectOutputStream.
Hope this helps,
Michael Morris

[Kunal Aher]

Thanks for the reply .
But I am using the ATG Dynamo app server and their Repository API. It is a layer above the DB ( similar to JDO ) , and the method signature that they have provided to insert binary data takes a byte[]. There is no method like setObject that can be used. So the deadlock.

Regards

[Peter den Haan]

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(foobar);
oos.flush();
oos.close();
byte[] serializedFoobar = bos.toByteArray();

- Peter

[Michael Morris]

Hi Kunal,
Well you can try something like this:
TestObject.java

import java.io.*;
public class TestObject implements Serializable {
    private byte b;
    private short s;
    private char c;
    private int i;
    private long l;
    private float f;
    private double d;
    private Object o;
    private String name;
    public TestObject(byte b, short s, char c, int i, long l, float f,
                      double d, Object o, String name) {
        this.b = b;
        this.s = s;
        this.c = c;
        this.i = i;
        this.l = l;
        this.f = f;
        this.d = d;
        this.o = o;
        this.name = name;
    }
    public byte getB() {
        return b;
    }
    public short getS() {
        return s;
    }
    public char getC() {
        return c;
    }
    public int getI() {
        return i;
    }
    public long getL() {
        return l;
    }
    public float getF() {
        return f;
    }
    public double getD() {
        return d;
    }
    public Object getO() {
        return o;
    }
    public String getName() {
        return name;
    }
    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("name=" + name + ";");
        sb.append("b=" + b + ";");
        sb.append("s=" + s + ";");
        sb.append("c=" + c + ";");
        sb.append("i=" + i + ";");
        sb.append("l=" + l + ";");
        sb.append("f=" + f + ";");
        sb.append("d=" + d + ";");
        sb.append("o=" + o + ";");
        return sb.toString();
    }
}

ObjectByteArray.java

import java.io.*;
public class ObjectByteArray {
    public static byte[] getBytes(Serializable object) throws IOException {
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bytes);
        oos.writeObject(object);
        oos.flush();
        oos.close();
        return bytes.toByteArray();
    }
    public static Object restore(byte[] bytes) throws Exception {
        ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
        ObjectInputStream ois = new ObjectInputStream(bais);
        Object object = ois.readObject();
        ois.close();
        return object;
    }
    public static void main(String[] args) throws Exception {
        TestObject to1 = new TestObject((byte) 23, (short) 247, 'M', 32451,
                                        33333L, 45.678F,  -2345.8,
                                        new Integer(-90), "to1");
        TestObject to2 = new TestObject((byte) -34, (short) -10000, 'F', -2376,
                                        -45690L, -0.123589F,  30865.8213,
                                        new Double(75.9), "to2");
        System.out.println("Before searializing:");
        System.out.println("\t" + to1);
        System.out.println("\t" + to2);
        System.out.println("");
        byte[] b1 = ObjectByteArray.getBytes(to1);
        byte[] b2 = ObjectByteArray.getBytes(to2);
        Object o1 = ObjectByteArray.restore(b1);
        Object o2 = ObjectByteArray.restore(b2);
        System.out.println("After searializing:");
        System.out.println("\t" + o1);
        System.out.println("\t" + o2);
    }
}

Hope this helps,
Michael Morris

[Kunal Aher]

Hi ,
Thanks . Its a great solution. I shall be trying
it out soon.
Let me share with you what I need this for. I am creating a few object , which will be the outcome of xml parsing , some DB lookups etc. But the data in them wont change regularly. So I though about this idea of storing those fully constructed objects in a secondary storage. And the next time I need those objects I will read them from the DB. Now the only thing left to do will be to compare the time to see if there are aany significant differences .The above soln. will allow me to go ahead with my idea.

Thanks once again .

Regards
[ March 04, 2003: Message edited by: Kunal Aher ]