TY.BSc.IT Java QB U3

QUESTION BANK
UNIT –III
Q.1 What are servlets?Whatare the advantages of usingservlets?
Ans: Java Servletsare programsthatrun on a Web or Application serverand act asa middle layer between a
requestcoming froma Web browserorother HTTP client and databasesorapplicationson theHTTP server.
 Servlets providea way to generatedynamicdocumentsthatisboth easier to write and fasterto
run.
 Provideall thepowerfullfeaturesof JAVA,such asException handling and garbagecollection.
 Servlet enableseasy portability acrossWeb Servers.
 Servlet can communicatewith differentservlet and servers.
 Since all web applicationsarestatelessprotocol,servlet usesits own APIto maintain session
Q.2 Explainthe lifecycle of servlet.
Ans: A servletlifecycle canbe definedasthe entire processfromitscreationtill the destruction.The following
are the pathsfollowedbyaservlet
 The servletisinitializedbycallingthe init() method.
The initmethodisdesignedtobe calledonlyonce.Itiscalledwhenthe servletisfirstcreated,andnot
calledagainforeach userrequest.
publicvoidinit() throwsServletException
{
// Initializationcode...
}
 The servletcalls service() methodtoprocessaclient'srequest.
The service() methodisthe mainmethodtoperformthe actual task.The servletcontainer(i.e.webserver)
callsthe service() methodtohandle requestscomingfromthe client( browsers)andtowrite the formatted
response backto the client.
publicvoidservice(ServletRequestrequest,ServletResponseresponse)
throwsServletException,IOException
{
// code...
}
 The servletisterminatedbycallingthe destroy() method.
The destroy() methodiscalledonlyonce atthe endof the life cycle of a servlet.Thismethodgivesyour
servletachance toclose database connections,haltbackgroundthreads,writecookie listsorhitcountsto
disk,andperformothersuch cleanupactivities.
publicvoiddestroy(){
// Finalizationcode...
}

Q.3 Write a servletprogram to display the simple sentence Welcome alongwiththe name enteredby the
user through an HTML form.
Ans: HTML CODE:
<form method=postaction=”DisplayServlet”>
<pre>
Enter yourName:<inputtype=textname=t1>
<inputtype=submitvalue=”Clickhere”>
</pre>
</form>
SERVLET CODE:
Importjavax.servlet.*;
Importjavax.servlet.http.*
Importjava.io.*;
PublicclassDisplayServletextendsHTTPServlet
{
PublicvoiddoPost(HTTPServletRequest req,HTTPServletResponse res)
throwsException{
res.setContentType("text/html");
PrintWriterout= res.getWriter();
Stringa=req.getParameter(“t1”)
out.println("<h1>Welcome “+ a + "</h1>");
}
}
Q.4 Explainthe followingelementsofthe web.xml file ofservlet
1. <servlet>
2. <servlet-mapping>
3. <session-config>
4. <welcome-file-list>
5. <web-app>
Ans: 1. <servlet>:
The servletelementcontainsthedeclarativedata of a servlet.
2. <servlet-mapping>:
The servlet-mapping elementdefinesa mapping between a servlet and a URL pattern.
3. <session-config>:
The session-config elementdefinesthesession attributesforthisWeb application.
4. <welcome-file-list>:
The welcome-file-listelementof web-app,isused to definea list of welcome files. Itssub

element iswelcome-filethatis used to definethe welcomefile.
5. <web-app>:
The XML Schema forthe Servlet2.4 deploymentdescriptor.WebLogicServerfully supports
HTTP servlets as defined in theServlet2.4 specification fromSun Microsystems.However,
theversion attributed mustbesetto 2.4 in orderto enforce2.4 behavior.
Q.5 What is CGI?Whatare the disadvantagesof CGI?
Ans:  The Common Gateway Interface(CGI) isan interfaceto the Web serverthatenablesyou to
extend theserver's functionality.
 Using CGI,you can interact with users who accessyoursite.
 CGI enablesyou to extend thecapability of yourserverto parse (interpret) inputfromthe
browserand return information based on userinput.
 CGI is an interfacethatenablesthe programmerto write programsthatcan easily
communicatewiththe server.
Disadvantages:
1. Responsetime is high,the creation of an Shell is an heavy weightactivity
2. CGI is not scalable
3. Notalwayssecureor object-oriented
4. No separation of presentation and businesslogic
5. Scripting languagesareoften platform-dependent
Q.6 Explainwith suitable diagram request/response paradigmof servlet
Ans: In theHTTP based request-responseparadigm,a clientuser agent(a web browseror any such application
thatcan makeHTTP requestsand receive HTTP responses) establishesa connection with a web server and
sendsa requestto theserver.
If the web server hasa mapping to a servlet forthe specified URL in the request,theweb server delegates
the requestto thespecified servlet.The servlet in turn processestherequestand generatesa HTTP
response.
HTTP Request: The interface HttpServletRequestisthe first abstraction provided by theservletAPI.When a
requestis received by the servlet engine,an objectof this typeis constructed and passed on to a servlet.
This objectprovidesmethodsforaccessing parameternamesand valuesof therequest & otherattributes
of the request.
HTTP Response: The HttpServletResponseinterfaceof theservletAPI providesan encapsulation of theHTTP
responsegenerated by a servlet. This interfacedefinesan objectcreated by the servlet enginethat lets a
servlet generatecontentin responseto a user agent'srequest.
ApplicationLogicandContent Generation: The HttpServletinterfacespecifies methodsforimplementing
the application logic and generating contentin responseto a HTTP request.
Q.7. Explainthe followingmethodof servletinterface
1.init
2.destroy
3.service
4.getServletConfig
5.getServletInfo
Ans: These are 5 methodsin Servlet interface. Servletinterfaceneeds to be implemented forcreating any servlet

(either directly or indirectly).It provides3 life cycle methodsthatare used to initialize the servlet, to service
the requests,and to destroy theservlet and 2 non-lifecycle methods.
1. Init() :
The init method isdesigned to be called only once.It is called when the servlet is first created,and not
called again foreach user request.
public void init() throwsServletException
{
// Initialization code...
}
2. Destroy():
The destroy() method iscalled only onceat the end of the life cycle of a servlet.This method givesyour
servlet a chanceto close databaseconnections,haltbackground threads,writecookielists or hit countsto
disk,and performothersuch cleanup activities.
public void destroy() {
// Finalization code...
}
3. Service():
The service() method is the main method to performthe actualtask.The servlet container(i.e.web server)
calls the service() method to handlerequestscoming fromthe client( browsers) and to write theformatted
responseback to the client.
public void service(ServletRequestrequest,ServletResponseresponse)
throwsServletException,IOException
{
// code...
}
4. getServletConfig():
An objectof ServletConfig iscreated by the web containerforeach servlet.This objectcan be used to get
configuration information fromweb.xmlfile.getServletConfig() method of Servletinterfacereturnsthe
objectof ServletConfig.
ServletConfig config=getServletConfig();
5. getServletInfo():
Returnsinformation abouttheservlet,such asauthor,version,and copyright.
The string that this method returnsshould beplain text and notmarkup of any kind (such asHTML, XML,
etc.).
public java.lang.String getServletInfo()
Q.8. Write a simple servletprogram that will displaythe factorial of a givennumber
Ans: HTML CODE:
<pre>
Enter anyNumber:<inputtype=”text”name=”t1”>
<inputtype=”submit”value=”Clickhere”>
</pre>
</form>
SERVLET CODE:
Importjava.io.*;

{
throwsException{
int a=Integer.parseInt(req.getParameter(“t1”));
Int fac=1;
for(inti=1;i<n;i++) {
fac=fac*i); }
out.println("<h1>Result“+ fac + "</h1>"); }
}
}
Q.9 What is the purpose ofHttpServletRequestinterface ofservletAPI? Explainwith suitable example
Ans:  publicinterface HttpServletRequestextends ServletRequest
 Extendsthe ServletRequestinterface toproviderequestinformationforHTTPservlets.
 The servletcontainercreatesan HttpServletRequestobjectandpassesitasan argumentto the
servlet'sservice methods(doGet, doPost,etc).
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet {
private String message;
public void init() throws ServletException
{
message = "Hello World";
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<h1>" + message + "</h1>");
}
public void destroy()
{
// do nothing.
}
}
Q.10 Write a servletprogram that will read a string from user. If the string is “Examination” thengreetthe
user otherwise displayerror message.
Ans: HTML CODE:
<pre>
Enter anyString:<inputtype=”text”name=”t1”>
</pre>
</form>
SERVLET CODE:

Importjava.io.*;
{
throwsException{
Stringa=req.getParameter(“t1”);
If(a==”Examination”)
{ out.println("<h1>Welcome “+ a + "</h1>"); }
else
{ out.println("<h1>ERROR </h1>"); }
}
}
Q.11 Explainthe reason why servletis preferredoverCGI
Ans:  Requestis run in a separatethread,so fasterthan CGIs
 Scalable,can servemany morerequests,
 Robustand ObjectOriented.
 Can be written in Java Programming language.
 Platformindependent.
 Accessto Logging Capabilities.
 Error handling and Security.
Q.12 Write a servletthat prints the sum of square of n integernumbers.
Ans: HTML CODE:
<pre>
Enter any Number:<inputtype=”text”name=”t1”>
</pre>
</form>
SERVLET CODE:
Importjava.io.*;
{
throwsException{
int a=Integer.parseInt(req.getParameter(“t1”));
Int res=0;
for(inti=0;i<n;i++) {
res=res+(i*i); }
out.println("<h1>Result“+ res + "</h1>"); }
}
}

Q.13 Explainthe methodthat RequestDispatcherinterface doesconsistof with the relevantcode specification
Ans: The RequestDispacherinterfaceprovidesthefacility of dispatching therequestto anotherresourceit may
be html,servlet or jsp.
METHODS:
 publicvoidforward(ServletRequestrequest,ServletResponse response)throws
ServletException,java.io.IOException: Forwardsa request froma servlet to anotherresource
(servlet,JSPfile, or HTML file) on the server.
 publicvoidinclude(ServletRequestrequest,ServletResponseresponse)throws
ServletException,java.io.IOException: Includesthecontentof a resource(servlet,JSPpage,or
HTML file) in theresponse.
Code Specification :
INDEX .HTML
<formaction="servlet1" method="post">
Name:<inputtype="text"name="userName"/><br/>
Password:<input type="password"name="userPass"/><br/>
<input type="submit"value="login"/>
</form>

LOGIN . JAVA
publicvoiddoPost(HttpServletRequest request, HttpServletResponseresponse)
throwsServletException, IOException {
String n=request.getParameter("userName");
String p=request.getParameter("userPass");
if(p.equals("servlet"){
RequestDispatcherrd=request.getRequestDispatcher("WelcomeServlet");
rd.forward(request, response);
}
else{
out.print("Sorry UserNameorPassword Error!");
RequestDispatcherrd=request.getRequestDispatcher("/index.html");
rd.include(request,response);
}
}
WELCOMESERVLET . JAVA
publicvoiddoPost(HttpServletRequest request, HttpServletResponseresponse)
throwsServletException, IOException {
String n=request.getParameter("userName");
out.print("Welcome"+n);
}

TY.BSc.IT Java QB U3

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TY.BSc.IT Java QB U3