Byte array of array of array of Object

Question

I have an Object array of Object array. I want to convert it into a byte array and then receive it back as array of Object array. I have used theObjectOutputStream in conjunction with the ByteArrayOutputStream to convert it into a byte array:

ByteArrayOutputStream b = new BAOS();
ObjectOutputStream o = new OOS();
o.writeObject(obj)  // obj being the array

Then when I try to read it, all that I get is the content of the first array only. Also the size of the object array received is equal to the size of the individual arrays.

I have tried using iteration for writeObject() but to no avail.

Ok, so further I have tried the multi dimensional array approach as well:

byte[] firstArr = new byte[1];
oos.writeObject(orgArr[0]);
firstArr = baos.toByteArray();
byte[] secondArr = new byte[1];
oos.writeObject(orgArr[1]);
secondArr = baos.toByteArray();
byte[] combined = new byte[2];
combined[0] = firstArr[0];
combined[1] = secondArr[1];

Both arrays are the same, of same length and both the firstArr and secondArr are Object arrays. So, the problem that I have is that when I deserialize it using:

ObjectInputStream ois = new ObjectInputStream(
                    new ByteArrayInputStream(om.nakedPayload));
Object[] list = (Object[]) ois.readObject();

The length of the array list returned is 38. Which is the length of either of the 2 arrays (firstArr/secondArr). Also, the data that it contains is just of the firstArr. The om.nakedPayload is the data which I read from a Kafka topic. We have a wrapper written here so essentially, it expects a byte[] for read/write purposes.

It's hard to tell what your bug is, if you only show a couple of lines of your code. — Dawood ibn Kareem
– Dawood ibn Kareem, Commented Aug 8, 2015 at 2:56
Understand that using "serialization" is pretty complicated stuff (and a bit buggy besides). Not for the faint of heart. — Hot Licks
– Hot Licks, Commented Aug 8, 2015 at 3:08

surlac · Accepted Answer · 2015-08-08 03:28:35Z

Let's simplify the task and assume your object is Integer, then the code for serializing/deserializing will look like following:

import java.io.*;

public class ArrayOfArrays {

    public static void main(String[] args) throws Exception{
        String fileName = "myobject.data";
        FileOutputStream fileOut = new FileOutputStream(fileName);
        ObjectOutputStream out = new ObjectOutputStream(fileOut);

        Integer[][] intArray = new Integer[3][3];
        intArray[0] = new Integer[] {11, 12, 13};
        intArray[1] = new Integer[] {21, 22, 23};
        intArray[2] = new Integer[] {31, 32, 33};

        out.writeObject(intArray);

        FileInputStream fileIn = new FileInputStream(fileName);
        ObjectInputStream in = new ObjectInputStream(fileIn);

        Integer[][] intArrayIn =  (Integer[][]) in.readObject();
    }
}

This will give same "array of arrays" object back. Next step we can replace Integer with any class which implements marker interface java.io.Serializable.

All non-transient fields will be involved in serialization/deserialization and restored along with root "array of arrays" object.

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