Request、Session 和 ServletContext 中的属性差异 [英] Differences between attributes in Request, Session and ServletContext

问题描述

我无法理解这 3 种设置属性的方法之间的区别:

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. 有何不同?
2. 你应该什么时候使用它们?

推荐答案

这三个有不同的作用域:

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

该会话生命周期内的会话属性

session attributes for the life of that session

ServletContext 跨越 servlet 上下文，它一直存在，直到上下文被销毁.

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

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