见开发社区的：issue 5:modify DAO tier
The DAO tier of "learndiary" is a bad design,difficult to understand,large
size,there are too many methods in a class,it affects the performance of our
program.It must be modified,although our entire system will be redesign in the
furture,but,for giving user a better experience of visiting our website,it
needs a quick fix.
为了改善网站的性能，减少内存占用，第一步是将LearnDiaryDB.java按对象和功能拆分开。
接下来...，再说。