Request，Session和ServletContext中的属性之间的差异 [英] Differences between attributes in Request, Session and ServletContext

问题描述

我无法理解这三种设置属性的方式之间的区别:

I am having trouble understanding the differences between these 3 ways of setting attributes:

// String as attribute of request
req.setAttribute("name", "Sluggo");

// Integer as attribute of session
req.getSession().setAttribute("age", 10);

// Date as attribute of context
getServletContext().setAttribute("today", new Date());

1. 有什么区别?
2. 何时应使用它们?

推荐答案

这三个具有不同的范围:

Those three have different scopes:

• 请求属性在该请求/响应周期的生命周期内有效

• request attributes live for the life of that request/response cycle

该会话有效期内的会话属性

session attributes for the life of that session

ServletContext跨servlet上下文，并且一直存在直到上下文被销毁为止.

ServletContext is across the servlet context and it lives until context gets destroyed.

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