Using Spring's IoC, instead of using my ugly service loader, adjusting
the hierarchy of interface and all implements.

JudgeService is being re-construction.
partly finsh judge service.

next is to write crawl and submit worker thread.
new database design.
Writing judge service
store change before rebuild
Change of database design, add some unique constraints.
Miner change of judge service.
Judge Service finished, but not tested.
Fix some missing part of judge service. Still un-tested.
As the @Transactional even if the method is public, but it is invoked
from the same been, it will not taken in account either (this statement
is only correct if (default) Spring Proxy AOP is used).

So, I changed the code using the DAOs. And, DAOs has also updated.
fixed some bugs after test
partly of these two days' work. about problem list.
Using strong type criteria query.
change some of the listing code.

writing about the front-end UI, however, the api of datatable is not
easy to learn.

in low progress.
fixed all bugs.
basically finish problem's display
some fix of showing the problem.
begin to writing the submit scenario, however, i fat up with the ugly
script of jquery-ui plugin, so, i am going to remove all of them
tomorrow.
removed struts-jquery plugin, finished front-end submit logic.

next is to write the action beans.
submit is ok.

but every update takes two select, can i optimize??