HttpServlet中 doGet() ?何谓safe and idempotent

HttpServlet中 doGet() ?何谓safe and idempotent

When a method is idempotent, in short, you are guaranteeing that regardless of when or how often it's used, no "side effects" will occur.

對每一個相同的query string
不管你執行多少次
所得到的結果要一樣

doPost()

This method does not need to be either safe or idempotent. Operations requested through POST can have side effects for which the user can be held accountable, for example, updating stored data or buying items online.