[Daily note] 2020-02-11-DailyNote in workspace

1. git commit rule
   • one commit = one deployment
2. test
   • white box = unit test
   • black box = integrated test
3. design pattern
   • singleton : make only once usage : like DBCP, using number of common object, easy to share data(thread pool,cache,user config,reg data, log)
   • Is DBCP(Database Connection pool) object??