Introduction to implicit objects by R4R Team

Introduction to implicit objects:

Implicit Objects and their corresponding classes:

out javax.servlet.jsp.JspWriter
request javax.servlet.http.HttpServletRequest
response javax.servlet.http.HttpServletResponse
session javax.servlet.http.HttpSession
application  javax.servlet.ServletContext
exception javax.servlet.jsp.JspException
page java.lang.Object
pageContext  avax.servlet.jsp.PageContext
config javax.servlet.ServletConfig

Out: This is used for writing content to the client (browser). It has several methods which can be used for properly formatting output message to the browser and for dealing with the buffer.
Request: The main purpose of request implicit object is to get the data on a JSP page which has been entered by user on the previous JSP page. While dealing with login and signup forms in JSP we often prompts user to fill in those details, this object is then used to get those entered details on an another JSP page (action page) for validation and other purposes.
Response: It is basically used for modfying or delaing with the response which is being sent to the client(browser) after processing the request.
Session: It is most frequently used implicit object, which is used for storing the userís data to make it available on other JSP pages till the user session is active.
Application: This is used for getting application-wide initialization parameters and to maintain useful data across whole JSP application.
Exception: Exception implicit object is used in exception handling for displaying the error messages. This object is only available to the JSP pages, which has isErrorPage set to true.
Page: Page implicit object is a reference to the current Servlet instance (Converted Servlet, generated during translation phase from a JSP page). We can simply use this in place of it. Iím not covering it in detail as it is rarely used and not a useful implicit object while building a JSP application.
pageContext: It is used for accessing page, request, application and session attributes.
Config: This is a Servlet configuration object and mainly used for accessing getting configuration information such as servlet context, servlet name, configuration parameters etc.

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