CODEWITHSUNDEEP
javaarraysbytebufferendianness
arsenal
arsenal

Reputation: 24144

How to use ByteBuffer properly?

I am trying to use ByteBuffer properly with BigEndian byte order format..

I have couple of fields which I am trying to put together into a single ByteBuffer before storing it in Cassandra database.

That Byte Array which I will be writing into Cassandra is made up of three Byte Arrays as described below-

short employeeId = 32767;
long lastModifiedDate = "1379811105109L";
byte[] attributeValue = os.toByteArray();

Now, I will write employeeId , lastModifiedDate and attributeValue together into a single Byte Array and that resulting Byte Array I will write into Cassandra and then I will be having my C++ program which will retrieve that Byte Array data from Cassandra and then deserialize it to extract employeeId , lastModifiedDate and attributeValue from it.

So to do this, I am using ByteBuffer with BigEndian byte order format.

I have put up this code together - 

public static void main(String[] args) throws Exception {

        String text = "Byte Buffer Test";
        byte[] attributeValue = text.getBytes();

        long lastModifiedDate = 1289811105109L;
        short employeeId = 32767;

        int size = 2 + 8 + 4 + attributeValue.length; // short is 2 bytes, long 8 and int 4

        ByteBuffer bbuf = ByteBuffer.allocate(size); 

        bbuf.order(ByteOrder.BIG_ENDIAN);
        bbuf.putShort(employeeId);
        bbuf.putLong(lastModifiedDate);
        bbuf.putInt(attributeValue.length);
        bbuf.put(attributeValue);

        bbuf.rewind();

        // best approach is copy the internal buffer
        byte[] bytesToStore = new byte[size];
        bbuf.get(bytesToStore);

        // write bytesToStore in Cassandra...

        // Now retrieve the Byte Array data from Cassandra and deserialize it...
        byte[] allWrittenBytesTest = bytesToStore;//magicFunctionToRetrieveDataFromCassandra();

        ByteBuffer bb = ByteBuffer.wrap(allWrittenBytesTest);

        bb.order(ByteOrder.BIG_ENDIAN);
        bb.rewind();

        short extractEmployeeId = bb.getShort();
        long extractLastModifiedDate = bb.getLong();
        int extractAttributeValueLength = bb.getInt();
        byte[] extractAttributeValue = new byte[extractAttributeValueLength];

        bb.get(extractAttributeValue); // read attributeValue from the remaining buffer

        System.out.println(extractEmployeeId);
        System.out.println(extractLastModifiedDate);
        System.out.println(new String(extractAttributeValue));

}

Is there any better way of doing this, the way I am doing it currently? Or some minor improvements that we can do it here??

This is the first time I am using ByteBuffer so having little bit problem...

Can anyone take a look and let me know whether this is the right way to use ByteBuffer?

Upvotes: 0

Views: 3047

Answers (1)

Peter Lawrey
Peter Lawrey

Reputation: 533472

The default order is always BIG_ENDIAN, so you don't meed to set it. Also when you wrap() is is already rewind()ed.

Instead of copying the underlying array, I would use the underlying array.

Replace

    bbuf.rewind();

    // best approach is copy the internal buffer
    byte[] bytesToStore = new byte[size];
    bbuf.get(bytesToStore);

with

    byte[] bytesToStore = bbuf.array();

Upvotes: 1

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