Exploring JSP built-in objects reveals their number divided into several

Overview of JSP built-in objects

JSP built-in objects are special objects provided by the JSP container for JSP pages. They contain information about JSP pages and servers. information, as well as some properties and methods for accessing and manipulating this information. JSP built-in objects are tools that JSP developers often use when writing JSP pages. They can help developers write JSP pages more easily and improve the performance and security of JSP pages.

Types of JSP built-in objects

There are many JSP built-in objects, and each built-in object has its specific purpose. Commonly used JSP built-in objects include:

• request: Represents the current HTTP request, which contains information about the HTTP request, such as request method, request URI, request parameters, etc.
• response: Indicates the current HTTP response, which contains information about the HTTP response, such as response status code, response header, response body, etc.
• session: Indicates the current HTTP session, which contains information about the HTTP session, such as session ID, session attributes, etc.
• application: Represents the current Web application, which contains information about the Web application, such as application name, application path, etc.
• config: Indicates the current JSP page configuration, which contains information about the JSP page configuration, such as the name of the JSP page, the path of the JSP page, etc.
• page: Indicates the current JSP page, which contains information about the JSP page, such as the name of the JSP page, the path of the JSP page, etc.
• out: Indicates the current JSP page output stream, which can be used to output content to the JSP page.
• exception: Indicates the current exception object, which contains information about the exception, such as exception type, exception message, etc.

Code examples for JSP built-in objects

Here are some code examples using JSP built-in objects:

<%
// 获取请求参数
String name = request.getParameter("name");

// 设置响应状态码
response.setStatus(200);

// 设置响应头
response.setHeader("Content-Type", "text/html");

// 获取会话属性
String value = (String) session.getAttribute("value");

// 获取应用程序属性
String contextPath = application.getContextPath();

// 获取JSP页面配置属性
String pageEncoding = config.getInitParameter("pageEncoding");

// 获取JSP页面名称
String pageName = page.getPageName();

// 向JSP页面输出内容
out.println("Hello, " + name);
%>

JSP built-in Precautions for using objects

When using JSP built-in objects, you need to pay attention to the following points:

• JSP built-in objects are thread-safe, which means that they can be Safe to use in multi-threaded environments.
• JSP built-in objects are read-only, which means they cannot be modified.
• JSP built-in objects are not serializable, which means they cannot be serialized and deserialized.
• JSP built-in objects are container-managed, which means they are created and destroyed by the JSP container.

Summary

JSP built-in objects are tools that JSP developers often use when writing JSP pages. They can help developers write JSPs more easily. page, and improve the performance and security of JSP pages. There are many built-in objects in JSP, and each built-in object has its specific purpose. When using JSP built-in objects, you need to pay attention to some considerations, such as JSP built-in objects are thread-safe, read-only, non-serializable and container-managed.

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