Implicit Objects in JSP are
those objects which are created/instantiated implicitly by the JSP
Engine or the container (part of the underlying Web Container and the container makes them available to the developers,) as a convenience feature
for the JSP page writers who can use them without having to instantiate
them. 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. But we can pass them to our own method if we
wish to use them locally in those functions. These implicit objects implement the interfaces defined in the
JSP/Servlet APIs.
There are nine implicit objects:
| Object | Class |
| Application | Javax.servlet.ServletContext |
| Config | Javax.servlet.ServletConfig |
| Exception | Java.lang.Throwtable |
| Out | Javax.servlet.jsp.JspWriter |
| Page | Java.lang.Object |
| PageContext | Javax.servlet.jsp.PageContext |
| Request | Javax.servlet.ServletRequest |
| Response | Javax.servlet.ServletResponse |
| Session | Javax.servlet.http.HttpSession |
1. 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 objects persists information across multiple user connection.
2. Responce: This object has a page scope that allows direct access to the HTTPServletResponce class object. Responce 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 a parameter.
3. 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() method.
4. 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 custom tag handlers. PageContext also provides access to several page attributes like including static or dynamic resource.
5. 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.
6. 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.
7. 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
parameters.
8. 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
pages."
9. 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.
