How to avoid BufferOverflow exception?

Question

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 need to snappy compress the attributeValue data before storing it in the Cassandra -

employeeId (do not snappy compressed)
lastModifiedDate (do not snappy compressed)
attributeValue  (snappy compressed it)

Now, I will write employeeId , lastModifiedDate and snappy compressed 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 decompress this attributeValue using snappy 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;

        // snappy compressing it and this line gives BufferOverflowException
        byte[] compressed = Snappy.compress(attributeValue);

        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(compressed); // storing the snappy compressed data

        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();

        // I am not sure whether the below read code will work fine or not..
        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(Snappy.uncompress(extractAttributeValue)));

}

Somehow the above code is throwing BufferOverflowException -

Exception in thread "main" java.nio.BufferOverflowException
    at java.nio.HeapByteBuffer.put(HeapByteBuffer.java:165)
    at java.nio.ByteBuffer.put(ByteBuffer.java:813)

Why I am snappy compressing the data before storing it in Cassandra because when I retrieve the data from Cassandra from C++ code, then it should be snappy compressed so it will take lot of less space in our C++ Map. And we will decompressed it only when people will make a call to us.

Can anybody take a look and let me know what wrong I am doing here? And how I should read the data back then?

Answer 1

You should be using the compressed length when allocating the original ByteBuffer.