What are the nine built-in objects of jsp and their functions

JSP nine built-in objects and their functions: 1. request object; 2. response object; 3. pageContext object; 4. session object; 5. application object; 6. out object; 7. config object; 8 , page object; 9. exception object. Detailed introduction: 1. The request object is used to obtain the client's request information. Its function is to obtain the data submitted by the user, as well as other information from the browser, etc. through this object.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

JSP (Java Server Pages) built-in objects, also called implicit objects, are special objects that can be used directly in JSP pages without creating them in advance. There are 9 built-in objects in JSP, namely: request, response, pageContext, session, application, out, config, page and exception.

1. Request object: used to obtain the client’s request information.

• Function: User-submitted data and other browser information can be obtained through this object.
• For example: String userName = request.getParameter("username");

2. response object: used to send a response to the client.

• Function: Can be used to set response header information, set the response MIME type, etc.
• For example: response.setContentType("text/html");

3. pageContext object: Provides unified access to other eight implicit objects.

• Function: It contains the other eight major objects, through which the other eight major objects can be accessed.

4. Session object: used to track the user’s session information.

• Function: You can share data between multiple pages and mark the user's session status.
• For example: session.setAttribute("username", userName);

5. Application object: Represents an object created after the server starts.

• Function: It exists throughout the running of the web application and can be used to store data shared by the entire web application.
• For example: application.setAttribute("userList", userList);

6. out object: used to output content to the client.

• Function: It is the outlet for the JSP page to send responses to the client, and can be used to output HTML, XML and other data.

7. config object: used to obtain the initialization parameters of the Servlet.

• Function: Can be used to obtain parameter values ​​configured in web.xml.
• For example: String dataBaseURL = config.getInitParameter("dataBaseURL");

8. Page object: represents the JSP page itself.

• Function: Can be used to jump within the page.

9. exception object: used to handle exceptions in JSP pages.

• Function: When the JSP page throws an exception, you can obtain the exception information through this object.
• Note: This object is only available in error pages. If this object is used in a normal JSP page, a compilation error will occur.
• For example: try { // some code that may throw an exception } catch (Exception e) { exception.printStackTrace(); // prints the stack trace to the error console }

The above are the nine built-in objects of JSP and their main functions. These built-in objects greatly simplify the development of JSP pages, allowing developers to focus more on the implementation of business logic.

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