Java Serializable Object to Byte Array

Java Serializable Object to Byte Array

Prepare the byte array to send:

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = null;
try {
  out = new ObjectOutputStream(bos);   
  out.writeObject(yourObject);
  out.flush();
  byte[] yourBytes = bos.toByteArray();
  ...
} finally {
  try {
    bos.close();
  } catch (IOException ex) {
    // ignore close exception
  }
}

Create an object from a byte array:

ByteArrayInputStream bis = new ByteArrayInputStream(yourBytes);
ObjectInput in = null;
try {
  in = new ObjectInputStream(bis);
  Object o = in.readObject(); 
  ...
} finally {
  try {
    if (in != null) {
      in.close();
    }
  } catch (IOException ex) {
    // ignore close exception
  }
}

Java: object to byte[] and byte[] to object converter (for Tokyo Cabinet)

public static byte[] serialize(Object obj) throws IOException {
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    ObjectOutputStream os = new ObjectOutputStream(out);
    os.writeObject(obj);
    return out.toByteArray();
}
public static Object deserialize(byte[] data) throws IOException, ClassNotFoundException {
    ByteArrayInputStream in = new ByteArrayInputStream(data);
    ObjectInputStream is = new ObjectInputStream(in);
    return is.readObject();
}

Converting from object to byte array and back in java

This should work, just cast the object to your class after receiving it from the serialize/deserialize function.

public static byte[] objToByte(TcpPacket tcpPacket) throws IOException {
    ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
    ObjectOutputStream objStream = new ObjectOutputStream(byteStream);
    objStream.writeObject(tcpPacket);

    return byteStream.toByteArray();
}

public static Object byteToObj(byte[] bytes) throws IOException, ClassNotFoundException {
    ByteArrayInputStream byteStream = new ByteArrayInputStream(bytes);
    ObjectInputStream objStream = new ObjectInputStream(byteStream);

    return objStream.readObject();
}

How to serialize objects together with byte array into a file?

Just serialize the byte array as an object, with writeObject() and deserialize with readObject(). That will take care of the length automatically.

Java: how to serialize object into byte array with as few output bytes as possible?

So is there some way in Java I can serialize object/array of objects efficiently and have the output byte array to be as short as possible?

Sure. What you need to do is write your own custom serialization code. For example, using a DataOutputStream you could serialize a byte[] like this:

   dos.writeInt(bytes.length);
   dos.write(bytes, 0, bytes.length);

and if the data was compressible then you could potentially do better.

For user-defined types, the serialization code will be more complex. But if you want "the output byte array to be as short as possible" ... then that is the price you have to pay!!

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The reason that ObjectOututStream streams are large is that it is a requirement that serialization / deserialization is type-safe; i.e. that it can detect cases where representation types have changed between serializing and deserializing. That is done by including server UUIDs and type descriptors in the stream. That takes space.

Note you (the programmer) can improve on the size of a serialized object by other means:

• by declaring unnecessary fields as transient,
• by writing a custom readObject / writeObject. or
• by declaring the class to be Externalizable, and implementing space efficient externalization methods.

Please refer to the Java Object Serialization spec for the details.

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