so, my questions are:
1. Give your opinion about my code, is there some thing wrong ?
2. I configure my application setting once, while the application start, I configure the application setting with appropriate reader (DbReader or PropertiesReader), I make it singleton. The problem is, While some user edit the database or file directly to database or file, I can't get the changed. now, I wanna implement like ApplicationSettingChangeListener. so if the data change, i will refresh reconfigure my application setting. do you have suggestion ?
The Apache Commons Configuration framework does all that you want: read from different type of data sources, reload on change, and much more.
If you've no compelling reason to roll out your own implementation, you're probably better off using that.