054：JSP九大内置对象-application其他 - 《Java基础回顾》

04-JSP内置对象-application及其他.ppt
九大内置对象：
out —-输出到客户端
request —-获取页面动态信息，url协议端口，
getRequestDispacher转发和重定向sendRedirect，乱码req.setCharacterEncoding(“UTF-8”);
response —重定向 setHeader定时刷新
setContentType(“application/msword”)响应数据类型session
session —会话时间，id，invalidate不可用,maxInactiveInterval()存活时间
Session有效性检验
application — 多会话数据共享 —留言板

page pageContext config exception
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Application
1、application:作用：
application对象实现了用户之间的数据的共享，可以存放全局变量
2、application主要用于维护全局信息：
多会话数据共享，session换成application 57KJX{4Z}SR036KW6(8(749.png

out.println(application.getRealPath(“/“))
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Exception
![BZE0{M4CZ~C)9[)(0L$CR.png](https://cdn.nlark.com/yuque/0/2021/png/22616587/1635952615010-1b2091bc-27b7-483f-898d-4d7d73c20152.png#clientId=u3577b642-0f72-4&from=paste&height=333&id=u97705776&margin=%5Bobject%20Object%5D&name=BZE0%7BM4CZ~C%29%609%5B%29%280L%60%24CR.png&originHeight=333&originWidth=1111&originalType=binary&ratio=1&size=73116&status=done&style=none&taskId=u6f8c341a-601d-422e-9cde-b90013deb18&width=1111)
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作用域极小==变量

面试：JSP四个存放对象的作用域
pageContext ——本页面
request ——一个请求内的，不重定向
session ——一个会话，一个浏览器
application ——多个会话之间

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