JSP Interview Questions and Answers

Created by JSP Engine during translation phase, while translating JSP to Servlet, JSP implicit objects are crafted inside service method and can be used directly within scriptlet without initializing and declaring them. In JSP, a total number of 9 implicit objects are available as following, Out, Request, Response, Session, Application, Exception, Page, pageContext, and config.

So many mechanisms are available through which the results of another page can be included in JSP.

There of primary mechanisms used by developers are

• Include directive
• jsp:include element
• Codas and preludes

This tag is required to use any Java object present in the JSP page.

The scope values for tag are as following: application, request, page, session, etc.

This action tag is used to instantiate or locate a bean class. Depending on the scope, it doesn’t create the bean if the bean object of the Bean class is already created. This JSP action tag has five attributes, which includes Id, Scope, Class, Type and Bean Name.

In JSP, the ServletContext shares information about the container in which the servlet is running in. This can be set up in the web application descriptor. There can be only one v ServletContext per web application. Compared to this, the PageContext gives the servlet information about the request that it is currently managing and contains information about the request, the response object, the session, and also a reference to the ServletContext of the web application.

• Custom tags are used to manipulate the JSP content, whereas Java beans can’t be manipulated.
• Java beans are easy to implement compared to custom tags which are tedious to implement.
• Custom tags contain self-contained behaviour, but Java beans are defined in one servlet and it is used in the JSP page or different servlet.

Based on function, JSTL tags are categorized into five types, which are Core Tags, Formatting and Localisation Tags, SQL Tags, XML Tags and Functions Tags.

To create a custom tag in JSP, use the following steps.

• Create the tag handler class first
• Then, create the TLD file
• Finally, create the JSP file

Developers can configure init params in JSP similar to the servlet in the web.xml file. We have to configure JSP init-params with servlet and servlet-mapping element. Put the JSP page location in the JSP-file element.