How do you restrict page errors display in the JSP page

You first set “Errorpage” attribute of PAGE directory to the name of the error page (ie Errorpage=”error.jsp”)in your jsp page .Then in the error jsp page set “isErrorpage=TRUE”. When an error occur in your jsp page it will automatically call the error page.

How many JSP scripting elements are there and what are they

There are three scripting language elements:

declarations, scriptlets, expressions.

What is JSP tag file

A source file containing a reusable fragment of JSP code that is translated into a tag handler when a JSP page is translated into a servlet.

What is JSP element

A portion of a JSP page that is recognized by a JSP translator. An element can be a directive, an action, or a scripting element.

What is JSP container

A container that provides the same services as a servlet container and an engine that interprets and processes JSP pages into a servlet.

What is JSP Implicit Objects

Certain objects that are available for the use in JSP documents without being declared first. These objects are parsed by the JSP engine and inserted into the generated servlet. The implicit objects re listed below:

request :It represents the request made by the client. The request implicit object is generally used to get request parameters, request attributes, header information and query string values.
response :The JSP implicit response object is an instance of a java class that implements the javax.servlet.http.HttpServletResponse interface. It represents the response to be given to the client. The response implicit object is generally used to set the response content type, add cookie and redirect the response.
pageContext : This is used to access page attributes and also to access all the namespaces associated with a JSP page. The lass or the interface name of the object PageContext is jsp.pageContext. The object PageContext is written: Javax.servlet.jsp.pagecontext The PageContext object has a page scope. It is an instance of the javax.servlet.jsp.PageContext class.
session :The session object has a scope of an entire HttpSession. It is an instance of the javax.servlet.http.HttpSession class. It represents the session created for the requesting client, and stores objects between client’s requests. The session object views and manipulates session information, such as the session identifier, creation time, and last accessed time. It also binds objects to a session, so that the user information may persist across multiple user connections.
application :The application object has an application scope. It is an instance of the javax.servlet.ServletContext class. It represents the context within which the JSP is executing. It defines a set of methods that a servlet uses to communicate with its servlet container.
out :The JSP implicit out object is an instance of the javax.servlet.jsp.JspWriter class. It represents the output content to be sent to the client. The out implicit object is used to write the output content.
config :The JSP implicit config object is an instance of the java class that implements javax.servlet.ServletConfig interface. It gives facility for a JSP page to obtain the initialization parameters available.
page :The Page object denotes the JSP page, used for calling any instance of a Page’s servlet. The class or the interface name of the Page object is jsp.HttpJspPage. The Page object is written: Java.lang.Object.
exception :The JSP implicit exception object is an instance of the java.lang.Throwable class. It is available in JSP error pages only. It represents the occured exception that caused the control to pass to the JSP error page.

What is the difference between and response.sendRedirect(url)?

The element forwards the request object containing the client request information from one JSP file to another file. The target file can be an HTML file, another JSP file, or a servlet, as long as it is in the same application context as the forwarding JSP file.

sendRedirect sends HTTP temporary redirect response to the browser, and browser creates a new request to go the redirected page. The response.sendRedirect also kills the session variables

Why is _jspService() method starting with an ‘_’ while other life cycle methods do not?

jspService() method will be written by the container hence any methods which are not to be overridden by the end user are typically written starting with an ‘_’. This is the reason why we don’t override _jspService() method in any JSP page.

Can we implement an interface in a JSP

Can you extend JSP technology

Yes. JSP technology lets the programmer to extend the jsp to make the programming more easier. JSP can be extended and custom actions & tag libraries can be developed to enhance/extend its features.