1.
What
is JSP?
Answer: Server-side running program
technology helps to create dynamic, platform independent web based
applications.
2.
What
is Servlet?
Answer: Servlet is a java program
runs on server, which receive request and send responses on HTTP protocol.
3.
Tell
me Servlet Life Cycle?
Answer: web server loads class->instantiate ()
-> calls init()-> calls service() on each request->calls destroy() on
unloading from server -> unloaded from server.
4.
Tell
me JSP Life Cycle?
Answer: jspInit() -> _jspService() ->
jspDestroy().
5.
What
is the difference doGet() and doPost()?
Answer:
doGet() –Used for query process,
which processes only HTTP GET requests which contains less input data like URL
params
doPost() –Used to send some data, do
some processes and get output. Processes HTTP POST requests which contains more
data.
6.
Have
you called Servlets in JSP?
Answer:
<%@ page import =
"javax.servlet.RequestDispatcher" %>
<% RequestDispatcher rd = request.getRequestDispatcher("/yourServletUrl");
request.setAttribute("msg","HI Welcome");
rd.forward(request, response);
%>
OR
OR
7.
How
will you declare a method inside JSP?
Answer:
Script let: Used to execute Java
code <% out.print(“HelloWorld JSP”)%>
Expression: Used to display on
output stream. <%= Calendar.getInstance().getTime()%>
Declaration: Used to declare methods
and variables <%! %>
8.
What
is mean by Single Thread Model in Servlet?
Answer: By default Servlets are
Multithreaded, i.e. single servlet responds for multiple requests. But we can
configure to instantiate each new instance for each requests (Single Threaded
Model) by implementing interface SingleThreadedModel.
9.
What
is Declaration in JSP?
Answer: Declaration: Used to declare methods and variables inside JSP and on compiling
they are placed outside _jspService method: syntax is <%! Int a=5;%>
10. After Compiling JSP, does declaration
available within _jspService method?
Answer: Declarations of methods and
variables will be place outside of the _jspService() method in the class file
after compilation.
11. How can two servlets communicate?
Answer:
RequestDispatcher rd =
servletContext.getRequestDispatcher("/pathToResource");
rd.forward(request, response);
Or
Response.sendRedirect(“URL”);
12. How a JSP page communicate with another
servlet?
Answer: Using
OR
RequestDispatcher rd =
servletContext.getRequestDispatcher("/pathToResource");
rd.forward(request, response);
OR
Response.sendRedirect();
13. Explain Servlet Container’s
Single-Thread Model and Multi-Thread Model?
Answer: All servlets by default
instantiated only once by the container and same one instance responds for all
incoming requests. But by implementing SingleThreadModel for each request new
instance will be created, serviced and destroyed.
14. What are the service methods in
HTTPServlet?
Answer:
doGet() – only for querying/getting data from server
doPost()- for posting data to the server and ask it to
process. Secured.
doPut()- Just add data into the URL
doHead() – get Header part of the
Get URL
doTrace() – traces loopback
doDelete() – Delete the requested
url
doOptions() – Get list of methods.
15. Difference between GenericServlet and
HTTPServlet?
Answer:
GenericServlet class implements Servlet, ServletConfig and Serializable
interfaces. GenericServlet class can handle any
type of request so it is protocol-independent.
But the HttpServlet class extends the GenericServlet class and implements
Serializable interface. It provides http specific methods.
16. Can init() method called many times?
Answer: Yes if u make
singlethreadedmodel. But by default called only once.
17. Use of "load-on-start-up" parameter
in Web.xml?
Answer: It denotes that servlet to
be loaded by container very first.
18. How do you manage Session in Servlets
and JSP?
Answer: Session is a conversation state between client and server and it
can consists of multiple request and response between client and server. Since
HTTP and Web Server both are stateless, the only way to maintain a session is
when some unique information about the session (session id) is passed between
server and client in every request and response.
a) Authenticating each time
b) Hidden fields in forms of jsp
c) Cookies
d) URL rewriting
e) Session API
19. How to use Cookies in JSP?
Answer:
Cookie cook = new Cookies(“userid”, “232314”);
Response.addCookie(cook);
So these will be stored in browser and will be returned each time.
Get Cookie:
Cookie cooks[] = Request.getCookies();
Delete Cookies:
Cooks[0].setMaxAge(200);
20. How to use HTTPSession in JSP?
Answer:
HttpSession session=request.getSession(false);
String n = (String)session.getAttribute("uname");
Also set value:
Session.setAttribute(“uId”,”12313123”);
21. What are the methods of HTTP Session?
Answer:
getAttribute(), setAttribute(),
isNew(), invalidated(), removeAttribute(), setMaxTime()
22. How will you send a request to
another servlet?
Answer:
RequestDispatcher rd= ServletContext.getRequestDispatcher(“URL”);rd.forward(req,resp);
23. What is the difference between
sendRedirect and forward method?
Answer: RequestDspatcher().forward –
happens inside container only.
Response.sendRedirect – server –
client – another server
24. Explain about Request-dispatcher?
Answer: An interface receive
requests from client and forwards to another resource on same server.
25. Explain about HTTPSession-Listener?
What are the methods?
Answer: Two methods:
sessionCreated(HttpSessionEvent e)
sessionDestroyed(HttpSessionEvent e)
26. What is the immediate super class of
HTTPServlet?
Answer: http.servlet.GenericServlet
class
27. What is the difference between
ServletContext and ServletConfig?
Answer:
ServletConfig – used by server to pass parameters to servlets while initializing,
available within the scope of Servlet.
ServletContext – contained by
servletConfig and used by .getContext(). Used by servlet to communicate with
container.
28. What do u mean implicit object and
list out implicit objects?
Answer:
Out – represents object of
javax.servlet.jsp.JspWriter and is used to send content in response.
Request –represents object of HttpServletRequest
sent from client.
Response – represents object of HttpServletResponse
produced by JSP to send to client.
Config – represents objects of
ServletConfig of the servlet of the JSP.
Application – represents ServletContext
Session – represtents the object of HttpSession
associated with the Servlet.
pageContext – PageContext – used to
set/remove attributes to any of the 4 scopes.
Ex:
pageContext.removeAttribute("attrName", PAGE_SCOPE);
page – represents “this” of the
servlet.
exception –Throwable- any exception
occurs will be catched and thrown to the “errorPage” if mentioned.
29. What is directive?
Answer:
The jsp directives are messages that
tells the web container how to translate a JSP page into the corresponding
servlet.
Page Directive: The page directive defines attributes that
apply to an entire JSP page
Ex: isErrorPage, errorPage, import, extends etc.,
Include Directive: The include directive is used to include the
contents of any other resource it may be jsp file, html file or text file<%@
include file=”header.jsp”>
TagLibrary: Declared tag libraries custme
actions.
30. What is mean by Custom Tag? What are
all the JSP Standard Tag Libraries?
Answer:
public class HelloTag extends SimpleTagSupport
{
public void doTag() throws
JspException, IOException
{
JspWriter out = getJspContext().getOut();
out.println("Hello
Custom Tag!");
}
}
WEB-INF/Custom.tld
1.0
2.0
Example TLD
Hello
com.tutorialspoint.HelloTag
empty
Test.jsp
<%@ taglib prefix="ex"
uri="WEB-INF/custom.tld"%>
A sample custom tag
31. What is EL & use?
Answer: Helps to use the POJO
varaibles in page. ${emp.FirstName}
32. What is mean by MVC Architecture in
JSP?
Answer:
Servlet as – Controller - will
receive request – validate – forms Model POJP Bean – Delegates to JSP 1 or JSP
2 based on the values.
JSP1.jsp or JSP2.jsp – as View
Employee.java – POJO as Model
33. I want to restrict a page should be
shown only when session exists, How to do that?
Answer: If we add page directive
session=false then we can restrict the session object creation in particular
JSP page.
34. I want to handle exceptions in JSP
page, How to do that?
Answer: Create a special error page
and add it using page directive errorPage=”err.jsp”.
So all errors will be redirected automatically to err.jsp. err.jsp page should include isErrorPage=”true”.
35. What are the two different ways to
include in JSP?
Answer:
1. Page Directive Include : <%@ include page=”header.jsp’/> - Static include
means will be included on compilation. And will be created as single servlet
class.
2. Tag library Include :< jsp:include page=”header.jsp”/> - Is runtime
inclusion, so content of the jsp/html file will be included into the output
writer.
36. Can session contain primitive types?
Answer:
HTTPSession session = new HTTPSession
();
Session.setAttribute (“regId”,
123123);
37. What are the types of scope s
available in JSP?
Answer:
Page – available within the same
page only. It exist from request creation to server processing. After server
process it dies.
Request – available within the request
i.e., if it forwarded to multiple pages it exists.
Session – Objects exists and live
from request creation to till the browser closed.
Application – Accessible from
multiple JSP pages of application, added to application context.
38. How will you declare variables and
method in JSP?
Answer: Using Declarations <%! Int
a=5; int add(int a,int b){ return a+b;}%>
39. How to access POJO beans in jsp?
Answer:
setValues to bean in JSP1.jsp
getValues from Bean and display in JSP2.jsp
You entered
Name: <%=
user.getUsername() %>
40. Have you used filters?
Answer: Yes. MyLogFilter
implements javax.servlet.Filter used to print log of all incoming request
details. It has three methods like servlets init(), doFilter() and destroy(). These
should have be configured in web.xml.
We can add
multiple listeners so they are all will be sequentially processed before the
request passed to the respective servlet.
41. What are the listeners you have used?
Answer: There
are
|
ServletRequestListener
|
requestInitalized
requestDestroyed
|
|
|
ServletRequestAttributeListener
|
attributeAdded
attributeRemoved
attributeReplaced
|
|
|
ServletContextListener
|
contextInitalized
contextDestroyed
|
|
|
ServletContextAttributeListener
|
attributeAdded
attributeRemoved
attributeReplaced
|
|
|
HttpSessionListener
|
sessionCreated
sessionDestroyed
|
|
|
HttpSessionAttributeListener
|
attributeAdded
attributeRemoved
attributeReplaced
|
|
|
HttpSessionBindingListener
|
valueBound
valueUnbound
|
|
|
HttpSessionActivationListener
|
|
|
