Mapping instance variables to buffer in external format

Question

I was inspired by this OP http://forum.java.sun.com/thread.jspa?threadID=5211760 to develop my first annotation. Having no experience
at all with annotations, I would like to ask you if it is something useful or
an abuse of annotations. I have my code at work and It works, but now I am at home, so here is the idea.
class TestByteMap
  @ByteMap.Offset(0) byte aByte;
  @ByteMap.Offset(1) int aInt;
  @ByteMap.Offset(5) short aShort;
  public static void main( String[] args )
    byte[] buffer = new byte[] {1, 2, 3, 4, 5, 6, 7};
    ByteMap bm = new ByteMap( new TestByteMap() );
    bm.fromBytes( buffer );  // Populate the annotated variables from byte array
    bm.toBytes( buffer ); // Dump annotated variables to byte array
}ByteMap is a class that has an inner annotation Offset. The toBytes()
and fromBytes() methods use reflection to move bytes between the
buffer and the annotated variables.
Thank you for any feedback!
Message was edited by:
baftos

Answer 1

If you need to read/write a class to a byte array, using annotations to mark which fields correspond to which offsets is somewhat better than tracking this by hand in comments. Instead of using reflection, you could mark the fields as before and use an annotation processor at compile time to generate the read/write methods appropriate for the class. In any case, it would be recommended to check for overlaps and other semantic errors in the offset annotations.