The basic type (int, String, etc.) stored in the session is different from the reference type (object).
1. basic type
session.setAttribute("test",1) -------》Object test = session.getAttribute("test") -------》test = 2 -------》system.out.print( session.getAttribute("test")); -------" The print result is: 1 (not 2)
2. reference type
Test test = new Test(); test.setName("小明"); session.setAttribute("test",test) -------》Object test2 = session.getAttribute("test") -------》test2.setName(‘xiaoming’); -------》system.out.print( session.getAttribute("test").getName()); -------" The print result is: xiaoming (the reference type will be automatically updated to the session field)