Implicit objects in jsp are the objects that are created by the container automatically and the container makes them available to the developers, the developer do not need to create them explicitly.
JSP Implicit Objects
Implicit objects in jsp are the objects that are
created by the container automatically and the container makes them available to
the developers, the developer do not need to create them
explicitly. Since these objects are created automatically by the
container and are accessed using standard variables; hence, they are called
implicit objects. The implicit objects are parsed by the container and
inserted into the generated servlet code. They are available only within the
jspService method and not in any declaration. Implicit objects are used for different purposes.
Our own methods (user defined methods) can't access them as they are local to
the service method and are created at the conversion time of a jsp into a
servlet. But we can pass them to our own method if we wish to use them locally
in those functions.
There are nine implicit objects. Here is the list of
all the implicit objects:
- Application: These objects has an application
scope. These objects are available at the
widest context level, that allows to share the same information between the
JSP page's servlet and any Web components with in the same application.
- Config: These object has a page scope and is
an instance of javax.servlet.ServletConfig class. Config object allows to pass the
initialization data to a JSP page's servlet. Parameters of this objects can
be set in the deployment descriptor (web.xml) inside the element <jsp-file>.
The method getInitParameter() is used to access the initialization
- Exception: This object has a page scope and
is an instance of java.lang.Throwable class. This object allows the
exception data to be accessed only by designated JSP "error
- Out: This object allows us to access the
servlet's output stream and has a page scope. Out object is an instance of
javax.servlet.jsp.JspWriter class. It provides the output stream that enable
access to the servlet's output stream.
- Page: This object has a page scope and is an instance of
the JSP page's servlet class that processes the current request. Page object
represents the current page that is used to call the methods defined by the
translated servlet class. First type cast the servlet before accessing any
method of the servlet through the page.
- Pagecontext: PageContext has a page scope.
Pagecontext is the context for
the JSP page itself that provides a single API to manage the various scoped
attributes. This API is extensively used if we are implementing JSP custom
tag handlers. PageContext also provides access to several page attributes
like including some static or dynamic resource.
- Request: Request object has a request scope
that is used to access the
HTTP request data, and also provides a context to associate the
request-specific data. Request object implements
javax.servlet.ServletRequest interface. It uses the getParameter() method to
access the request parameter. The container passes this object to the _jspService()
- Response: This object has a page scope that allows direct access to
the HTTPServletResponse class object. Response object is an instance
of the classes that implements the javax.servlet.ServletResponse class.
Container generates to this object and passes to the _jspService() method as
- Session: Session object has a session scope
that is an instance of javax.servlet.http.HttpSession class. Perhaps it is the most commonly used
object to manage the state contexts. This object persist information across
multiple user connection.