JSP Interview questions and answer

1. What is JSP?

JSP stands for Java Server Pages. JSP is java server side technology to create dynamic web pages. 

JSP file compiled by JSP container and convert it into servlet file.

2. What are the advantages of JSP?

JSP page is more suitable for create web pages and it is allows HTML tags, Servlet code and XML. 

JSP always compile before its process and the length of code is reduced by using custom tags and tag library.Java components can be easily embedded into the dynamic pages.

3. What is the JSP life cycle?

jspInit(): When a container loads a JSP it invokes the jspInit() method before servicing any requests.                                                                                                                   _jspService(): Whenever a browser requests a JSP and the page has been loaded and initialized, the JSP engine invokes the _jspService() method in the JSP. The _jspService() method is invoke once per a request and is responsible for generating the response for that request.                                                                                                                                   jspDestroy(): When a JSP is being removed from use by a container then jspDestroy() method will call.

4. Why _jspService() method starts with “_” ?

_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.

5. Can we override JSP lifecycle methods?

We can override jspInit() and jspDestroy() methods using JSP declaration scripting element.

6. Is JSP technology extensible?

JSP technology is extensible through the development of custom actions, or tags, which are encapsulated in tag libraries.

7. What is the difference between Servlet and JSP?

JSP	Servlet
JSP run slower, it takes compilation time to convert into Java Servlets.	Servlets run faster
JSP act as a view in MVC	Servlet act as a controller in MVC
JSP allows HTML, java code, XML	Servlet allows java code only
In JSP we can build custom tag	There is no such custom tag facility in servlets
Length of the code will be reduce by custom tags	There is no facility

8. What are the differences between JSP and ASP?

JSP - Java Server Pages	ASP - Active Server Pages
JSP is java technology and it is a server side scripting language developed by Sun Microsystems	ASP is .Net technology and it is a server side scripting language developed by Microsoft
JSP is  platform independent and can run on any platform	ASP runs on only Microsoft Windows platform
Java Server Pages runs on Apache Tomcat server	Active Server Pages runs on IIS (Internet Information Server)
We can connect it to any data base through drivers(libraries)	We can connect ASP to MS SQL or any other database with the help of ADO (ActiveX data object)
High security and easy to maintenance	Low security and hard to maintenance
Open source and we can build custom tag	It is cost and no custom tag facility

9. What is scriptlet syntax in JSP?

Scriptlet is useful to write the java program statements, declarations and expressions.

Syntax: <% write java code here %>

10. What is the syntax for comments in JSP?

JSP comment is useful when you want to hide or "comment out" part of your JSP page.

Syntax: <%-- comment anything here in JSP file --%>

11. What is an output comment?

A comment is sent to the client in the viewable page source. The JSP engine handles an output comment and returning the comment in the HTML output (browser page source) sent to the client.

Syntax: <!-- output comment -->

12. What is a Hidden Comment?

A comment that documents the JSP page but is not sent to the client. The JSP engine ignores a hidden comment, and does not process any code within hidden comment tags.

Syntax: <%-- hidden comment --%>

13. What is JSP Expression?

JSP expression contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file.

Syntax: <%= expression %>

14. What are the JSP directives?

Page: Defines page-dependent attributes, such as scripting language, error page, and buffering requirements.

<%@page contentType=" "%>

Include: include a jsp file into another jsp file.

<%@include file=" " %>

Taglib: Declares a tag library, containing custom actions, used in the page.

<%@ taglib uri=" " prefix=" " %>

15. Can we include a JSP page into another JSP page?

Yes, we can include by using include directive.

<%@include file=" " %>

16. What are the implicit objects?

Implicit 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. 

Implicit objects are:
1. request
2. response
3. pageContext
4. session
5. application
6. out
7. config
8. page
9. exception