说明：  最简单的EL表达式入门笔记，与其看太多繁琐的纸质书籍和电子书籍，还不如直接看这个笔记，百分百能直接上门。
(EL expression is the simplest entry notes, watch too much red tape to its paper books and electronic books, not as a direct look at the notes, full directly to your door.)