Reading fields from bytearray

Question

I am trying to send a message via tcp. Unfortunately that does not work and hence I have created the following code for test purposes:

    public void sendQuestion(String text) {
        // Set timestamp.
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
        TimeZone tz = TimeZone.getTimeZone("GMT+01:00");
        df.setTimeZone(tz);
        String date = df.format(new Date());

        byte[] dateStr = date.getBytes();

        // Set payload.
        String payloadTemp = date + text;
        byte[] payload = payloadTemp.getBytes();

        // Send the payload.
        clientOutputThread.send(1, payload);

           ....
    }   


 public void send(byte type, byte[] payload) {
            // Calculate and set size of message.
            ByteBuffer bufferTemp = ByteBuffer.allocate(4);
            bufferTemp.order(ByteOrder.BIG_ENDIAN);
            byte[] payloadSize = bufferTemp.putInt(payload.length).array();

            byte[] buffer = new byte[5 + payload.length];

            System.arraycopy(payloadSize, 0, buffer, 0, 4);
            System.arraycopy(payload, 0, buffer, 5, payload.length);

            // Set message type.
            buffer[4] = type;

            // TEST: Try reading values again

            ByteBuffer bb = ByteBuffer.wrap(buffer);  
            // get all the fields:
            int payload2 = bb.getInt(0);  // bytes 0-3
                                         // byte 4 is the type
            byte[] tmp = new byte[19]; // date is 19 bytes
            bb.position(5);
            bb.get(tmp); 
            String timestamp = tmp.toString();
            byte[] tmp2 = new byte[payload2-19];
            bb.get(tmp2); // text
            String text = tmp2.toString();

                    ....
}

Unfortunately, what I read as timestamp and text is rubbish, something of the sort of "[B@44f39650". Why? Am I reading wrong?

Thank you!

score 0 · Accepted Answer · answered Dec 03 '12 at 09:39

0

"[B@44f39650" is the result of calling toString() on an object which is a byte array. Which you are doing here:

String timestamp = tmp.toString();

So don't do that. Convert the byte array to a String, if you must do that at all, using the String constructors provided for the purposes.

However you should really be using the API of DataOutputStream and DataInputStream for this purpose.

answered Dec 03 '12 at 09:39

user207421

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thanks, that worked :) Not so sure how DataInputStream can help me here though, since that does not provide a method to read in a String either, does it? – user1809923 Dec 03 '12 at 12:25
@user1809923 It can help you because it has `readInt()`, `readUTF()`, `readXXX()` for quite a few types of XXX. `readUTF()` returns a `String`, provided you wrote it with `writeUTF()`. – user207421 Dec 04 '12 at 04:01

Reading fields from bytearray

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