Metacat

I noticed that when you use the export function in metacat, if the docid you
provide is not part of an eml package, it throws an exception and will not
export the file. I changed this so that it will zip up the individual file and
return that. Jing, would you please look at the changes I made to your code and
make sure I didn't break anything. The code is in the branch
CHANGES_FOR_MONARCH_01062003. Included in this branch is also the web.xml file
that works with Tomcat 4.x. Once the code in DBQuery is checked, it can be
merged into the trunk.