jsp防止重复提交 这做最好结合让jsp页面过期一起用。当用户返回到上一表单页面时（按backspase键、返回按钮，右击--返回），让表单页面过期。这样才可以让用户主动的刷新jsp而从新生成一个session.setAttribute("flag").如果不这样flag值不会更新，返回以后的操作数据是不会更新到数据库的。

（页面过期的机制还不完全了解，只知道一种实现方法但觉得不怎么好使。摸索中...)希望有人能提出更好的解决方法.让页面form的、session的flag更新。 -jsp to prevent duplicate submissions that do the best combination of jsp page expire together with. When the user returns to the previous form page (press backspase button, return button, right-click- return), so that form page has expired. Only in this way allows the user to take the initiative to refresh jsp newly generated a session.setAttribute (" flag" ). If no such flag value is not updated after they return from operational data is not updated to the database. (Page expired mechanism is not fully understood, and only know one method, but am not very good so that the groping ...) I hope someone can propose a better solution. Page form the session flag update.