public static String id(Resource res){
  String str=ResourceUtil.getCanonicalPathEL(res) + "|" + res.length()+ "|"+ res.lastModified();
  try {
    return Hash.md5(str);
  }
 catch (  NoSuchAlgorithmException e) {
    return Caster.toString(HashUtil.create64BitHash(str));
  }
}

public static String id ( Resource res ) { String str = ResourceUtil . getCanonicalPathEL ( res ) + "|" + res . length ( ) + "|" + res . lastModified ( ) ; try { return Hash . md5 ( str ) ; } catch ( NoSuchAlgorithmException e ) { return Caster . toString ( HashUtil . create64BitHash ( str ) ) ; } }
does not involve the content to create an id , value returned is based on metadata of the file ( lastmodified , size )
