Building Identical JAR file

Hi All,

I've a quick question. I need to build the ojb component from source. To
achieve this I download the source from
http://archive.apache.org/dist/db/ojb/db-ojb-1.0.3/db-ojb-1.0.3-src.zip
and run the "ant jar" command. This builds me a jar file however when I
compare it to the jar file in the located in the distribution here
http://archive.apache.org/dist/db/ojb/db-ojb-1.0.3/db-ojb-1.0.3.jar ,
there's a number of additional files in the jar downloaded from the
archive. Even when I use the ant command "ant with-jdori" I get a
different build in terms of file contents.
Can anyone tell me how to build a jar from source that is identical in
contents to the jar file in the distribution
Thanks in advance,
Michael