Best JSP Interview Questions

Question: What do you understand by JSP Actions?
Answer: JSP actions are XML tags that direct the server to use existing components or control the behavior of the JSP engine. JSP Actions consist of a typical (XML-based) prefix of "jsp" followed by a colon, followed by the action name followed by one or more attribute parameters.





There are six JSP Actions:













Question: What is the difference between and
<%@ include file = ... >?.
Answer: Both the tag includes the information from one page in another. The differences are as follows:
: This is like a function call from one jsp to another jsp. It is executed ( the included page is executed and the generated html content is included in the content of calling jsp) each time the client page is accessed by the client. This approach is useful to for modularizing the web application. If the included file changed then the new content will be included in the output.

<%@ include file = ... >: In this case the content of the included file is textually embedded in the page that have <%@ include file=".."> directive. In this case in the included file changes, the changed content will not included in the output. This approach is used when the code from one jsp file required to include in multiple jsp files.


Question: What is the difference between and
response.sendRedirect(url),?.
Answer: 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 kills the session variables.


Question: Identify the advantages of JSP over Servlet.

a) Embedding of Java code in HTML pages
b) Platform independence
c) Creation of database-driven Web applications
d) Server-side programming capabilities

Answer :- Embedding of Java code in HTML pages





Question: What are implicit Objects available to the JSP Page?
Answer: Implicit objects are the objects available to the JSP page. These objects are created by Web container and contain information related to a particular request, page, or application. The JSP implicit objects are:Variable Class Description
application javax.servlet.ServletContext The context for the JSP page's servlet and any Web components contained in the same application.
config javax.servlet.ServletConfig Initialization information for the JSP page's servlet.
exception java.lang.Throwable Accessible only from an error page.
out javax.servlet.jsp.JspWriter The output stream.
page java.lang.Object The instance of the JSP page's servlet processing the current request. Not typically used by JSP page authors.
pageContext javax.servlet.jsp.PageContext The context for the JSP page. Provides a single API to manage the various scoped attributes.
request Subtype of javax.servlet.ServletRequest The request triggering the execution of the JSP page.
response Subtype of javax.servlet.ServletResponse The response to be returned to the client. Not typically used by JSP page authors.
session javax.servlet.http.HttpSession The session object for the client.



Question: What are all the different scope values for the tag?
Answer: tag is used to use any java object in the jsp page. Here are the scope values for tag:
a) page
b) request
c) session and
d) application


Question: What is JSP Output Comments?
Answer: JSP Output Comments are the comments that can be viewed in the HTML source file.
Example:

and



Question: What is expression in JSP?
Answer: Expression tag is used to insert Java values directly into the output. Syntax for the Expression tag is:
<%= expression %>
An expression tag contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file. The following expression tag displays time on the output:
<%=new java.util.Date()%>


Question: What types of comments are available in the JSP?
Answer: There are two types of comments are allowed in the JSP. These are hidden and output comments. A hidden comments does not appear in the generated output in the html, while output comments appear in the generated output.
Example of hidden comment:
<%-- This is hidden comment --%>
Example of output comment:



Question: What is JSP declaration?
Answer: JSP Decleratives are the JSP tag used to declare variables. Declaratives are enclosed in the <%! %> tag and ends in semi-colon. You declare variables and functions in the declaration tag and can use anywhere in the JSP


Question: What are the life-cycle methods of JSP?
Answer: Life-cycle methods of the JSP are:
a) jspInit(): The container calls the jspInit() to initialize the servlet instance. It is called before any other method, and is called only once for a servlet instance.
b)_jspService(): The container calls the _jspservice() for each request and it passes the request and the response objects. _jspService() method cann't be overridden.
c) jspDestroy(): The container calls this when its instance is about to destroyed.
The jspInit() and jspDestroy() methods can be overridden within a JSP page.