On 3/7/2013 2:10 PM, mike wrote:
I am sending a command to unix and then I parse the output. The
output is stored in a Info object ( Info.java). This will be used
later in application.
The problem is that the output from the unix command might change. So
I want to make sure that if there is a change then we parse and
update the Info object. But if there is no change then we do not need
to parse and extract the information. We can use the Info object
directly.
The idea I have is to use the output from the command ( a text
string) and calculate some kind of hash/md5sum.
So the next time I run the unix command I take the output (a string)
and calculate hash/md5 and see if it is an exact match as was
generated the first time.
Anyone will to give a hint on how to implememt this using java?
You will need to code your logic, but hashing a String is easy:
MessageDigest md = MessageDigest.getInstance("SHA-256");
byte[] hash = md.digest(data.getBytes());
or maybe:
MessageDigest md = MessageDigest.getInstance("SHA-256");
String hash = toHex(md.digest(data.getBytes()));
...
private static String toHex(byte[] ba) {
char hexdigit[] = { '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
StringBuffer sb = new StringBuffer("");
for (int i = 0; i < ba.length; i++) {
sb.append(hexdigit[(ba[i] >> 4) & 0x0F]);
sb.append(hexdigit[ba[i] & 0x0F]);
}
return sb.toString();
}