What Are Implicit Objects

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∟What Are Implicit Objects

This section describes implicit objects that are created by the JSP/Servlet container: out, request, response, pageContext, session, application, and config.

What Are Implicit Objects? Implicit objects are data objects are created by the JSP/Servlet container so that you can use them interact with the execution environment.

Here is a list of implicit objects supported in JSP:

this: An object of the Servlet class converted from the JSP page representing this running Servlet instance.
page: Same at "this". An object of the Servlet class converted from the JSP page representing this running Servlet instance.
out: A javax.servlet.jsp.JspWriter object representing the output stream to collect dynamic data to be mixed static data in the JSP page to form the final Web document.
request: A javax.servlet.http.HttpServletRequest object representing the request received from the Web browser.
response: A javax.servlet.http.HttpServletResponse object representing the response to be delivered back to the Web browser.
pageContext: A javax.servlet.jsp.PageContext object representing the execution environment of this Servlet.
session: A javax.servlet.http.HttpSession object representing the concept of linking multiple trips of requests and response into a single process unit.
application: A javax.servlet.ServletContext object representing the concept of grouping multiple Servlets into a single application.
config: A javax.servlet.ServletConfig object representing the configuration of this JSP page.

Some commonly used methods provided by those implicit objects are listed below:

// Insert a string into the outgoing response body
out.println(String string);

// Retrieve all cookies as an array from the incoming request
request.getCookies();

// Retrieve the query string included in the request URL
request.getQueryString()

// Add a cookie to the outgoing response
response.addCookie(Cookie cookie)

// Set a HTTP header to the outgoing response
response.setHeader(String name, String value)

// Retrieve the session ID associated with this session
session.getId();

// Save an object into the session for later use
session.setAttribute(String name, Object value);

// Retrieve an object previously saved in the session
session.getAttribute(String name);

// Retrieve the name and version of the Servlet container
application.getServerInfo()

// Save an object into the application for other Servlets
application.setAttribute(String name, Object value);

// Retrieve an object previously saved by other Servlets
application.getAttribute(String name);