Decrypt the number of JSP built-in objects. How many are there in total?
JSP built-in objects are a very important part of JSP technology. They provide access to various system information and functions. The number of JSP built-in objects is 9, which are:
- request: Indicates the request currently being processed. It provides access to request parameters, request headers, request protocols, request methods and other information.
- response: Indicates the response to the current request. It provides access to response headers, response status, response body, and other information.
- session: Indicates the session with the current client. It provides access to information such as session properties, session IDs, etc.
- application: Indicates the current web application. It provides access to information such as application properties, application initialization parameters, and more.
- config: Indicates the configuration information of the current JSP page. It provides access to information such as page initialization parameters, page scope attributes, etc.
- page: Indicates the current JSP page. It provides access to information such as page-wide properties, page output streams, and more.
- out: Indicates the output stream of the current JSP page. It provides methods to send output to the client.
- exception: Indicates the exception that occurred in the current JSP page. It provides access to exception information, exception type, and other information.
- pageContext: Indicates the context of the current JSP page. It provides access to all other JSP built-in objects.
The following is a simple JSP page example to illustrate how to use these built-in objects:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>JSP内置对象示例</title>
</head>
<body>
<h1 id="JSP内置对象示例">JSP内置对象示例</h1>
<p>请求参数：${requestScope.name}</p>
<p>请求头：${requestScope.header['User-Agent']}</p>
<p>请求协议：${requestScope.protocol}</p>
<p>请求方法：${requestScope.method}</p>
<p>响应状态：${responseScope.status}</p>
<p>会话ID：${sessionScope.id}</p>
<p>应用程序名称：${applicationScope.name}</p>
<p>页面初始化参数：${configScope.param.name}</p>
<p>页面范围属性：${pageScope.name}</p>
<p>异常信息：${exceptionScope.message}</p>
</body>
</html>In this example, we use the following JSP built-in objects:
- request: used to obtain request parameters and request header information.
- response: used to obtain response status information.
- session: Used to obtain session ID information.
- application: used to obtain application name information.
- config: Used to obtain page initialization parameter information.
- page: Used to obtain page range attribute information.
- exception: Used to obtain exception information.
Through these JSP built-in objects, we can easily obtain various system information and functions, thereby conveniently developing JSP pages.
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