Implicit objects are a set of Java objects that the JSP Container makes
available to developers in each page. These objects may be accessed as built-in
variables via scripting elements and can also be accessed programmatically by
JavaBeans and Servlets.
Overview
Implicit objects will be automatically instantiated under specific variable
names. Furthermore,each object
must adhere to a specific Java class or interface definition.
We have already met one of these objects already - the out object in which we
used the println() method to add text to the output stream.
Object
Class or Interface
Description
page
jsp.HttpJspPage
Page's servlet instance
config
ServletConfig
Servlet configuration information
pageContext
jsp.pageContext
Provides access to all the namespaces associated with a JSP
page and access to several page attributes
request
http.HttpServletRequest
Data included with the HTTP Request
response
http.HttpServletResponse
HTTP Response data, e.g. cookies
out
jsp.JspWriter
Output stream for page context
session
http.HttpSession
User specific session data
application
ServletContext
Data shared by all application pages
The first three are rarely used. The application,
session and request implicit objects have the additional
ability to hold arbitrary values. By setting and getting attribute values these
objects are able to share information between several JSP pages.
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