WEB TECHNOLOGIES Servlet

Servlet
Common Gateway Interface (CGI), Lifecycle of a Servlet, deploying a servlet, The Servlet API, Reading Servlet parameters, Reading Initialization parameters, Handling Http Request & Responses, Using Cookies and Sessions, connecting to a database using JDBC.

1. WEB TECHNOLOGIES Servlet
Dr R Jegadeesan Prof-CSE
Jyothishmathi Institute of Technology and Science,
karimnagar

2. Syllabus
UNIT–IIIServlet
CommonGatewayInterface(CGI),
LifecycleofaServlet,deployinga
servlet,TheServletAPI,Reading
Servletparameters,Reading
Initializationparameters,Handling
HttpRequest&Responses,Using
CookiesandSessions,connectingto
adatabaseusingJDBC.
2

3. UNIT -III : Servlet Programming
Aim&Objective:
➢TointroduceServerSideprogrammingwithJavaServlets.
➢ServletTechnologyisusedtocreatewebapplications.Servlet
technologyusesJavalanguagetocreatewebapplications.
Introduction to Java Servlet
3

4. UNIT -III : Servlet Programming
Webapplicationsarehelperapplicationsthatresidesatwebserverandbuilddynamicwebpages.
Adynamicpagecouldbeanythinglikeapagethatrandomlychoosespicturetodisplayorevena
pagethatdisplaysthecurrenttime.
Introduction to Servlet
4

5. UNIT -III : Servlets
BeforeServlets,CGI(Common GatewayInterface)programmingwasusedtocreatewebapplications.
Here'showaCGIprogramworks:UserclicksalinkthathasURLtoadynamicpageinsteadofastatic
page.TheURLdecideswhichCGIprogramtoexecute.
WebServersruntheCGIprograminseparateOSshell.TheshellincludesOSenvironmentandthe
processtoexecutecodeoftheCGIprogram.TheCGIresponseissentbacktotheWebServer,which
wrapstheresponseinanHTTPresponseandsenditbacktothewebbrowser.
CGI (Common Gateway Interface)
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6. UNIT -III : Servlet
•Less response time because each request runs in a separate thread.
•Servlets are scalable.
•Servlets are robust and object oriented.
•Servlets are platform independent.
Advantages of Servlet
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7. UNIT -III : Servlet
Servlet API consists of two important packages that encapsulates all the important classes and
interface, namely :
javax.servlet
javax.servlet.http
Servlet API
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INTERFACES CLASSES
Servlet ServletInputStream
ServletContext ServletOutputStream
ServletConfig ServletRequestWrapper
ServletRequest ServletResponseWrapper
ServletResponse ServletRequestEvent
ServletContextListenerServletContextEvent
RequestDispatcher ServletRequestAttributeEvent
SingleThreadModel ServletContextAttributeEvent
Filter ServletException
FilterConfig UnavailableException
FilterChain GenericServlet
ServletRequestListene
r

8. UNIT -III : Servlet
Servlet Interface provides five methods. Out of these five methods, three methods are Servlet life
cyclemethods and rest two are non life cycle methods.
Servlet Interface
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9. UNIT -III : Servlet
WebcontainerisresponsibleformanagingexecutionofservletsandJSPpagesforJavaEEapplication.
Whenarequestcomesinforaservlet,theserverhandstherequesttotheWebContainer.WebContaineris
responsibleforinstantiatingtheservletorcreatinganewthreadtohandletherequest.ItsthejobofWeb
Containertogettherequestandresponsetotheservlet.Thecontainercreatesmultiplethreadstoprocess
multiplerequeststoasingleservlet.
Servletsdon'thaveamain()method.WebContainermanagesthelifecycleofaServletinstance.
How a Servlet Application Works
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10. UNIT -III : Servlet
Life Cycle of Servlet
10
LoadingServletClass:AServletclassisloadedwhenfirstrequestfortheservletis
receivedbytheWebContainer.
Servletinstancecreation:AftertheServletclassisloaded,WebContainercreatesthe
instanceofit.Servletinstanceiscreatedonlyonceinthelifecycle.
Calltotheinit()method:init()methodiscalledbytheWebContaineronservlet
instancetoinitializetheservlet.

11. UNIT -II : XML
Signatureofinit()method:
publicvoidinit(ServletConfigconfig)throwsServletException
Calltotheservice()method:Thecontainerscalltheservice()methodeachtimetherequestfor
servletisreceived.Theservice()methodwillthencallthedoGet()ordoPost()methosbasedont
ehtypeoftheHTTPrequest,asexplainedinpreviouslessons.
Signatureofservice()method:
publicvoidservice(ServletRequestrequest,ServletResponseresponse)throwsServletException,
IOException
Calltodestroy()method:TheWebContainercallthedestroy()methodbeforeremovingservlet
instance,givingitachanceforcleanupactivity.
Life cycle of Servlet
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12. UNIT -III : Servlet
GenericServlet is an abstract class that provides implementation of most of the basic servlet
methods. This is a very important class.
Methods of GenericServlet class
public void init(ServletConfig)
public abstract void service(ServletRequest request,ServletResposne response)
public void destroy()
public ServletConfig getServletConfig()
public String getServletInfo()
public ServletContext getServletContext()
public String getInitParameter(String name)
public Enumeration getInitParameterNames()
public String getServletName()
public void log(String msg)
public void log(String msg, Throwable t)
GenericServlet Class
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13. UNIT -III : Servlet
HttpServletisalsoanabstractclass.Thisclassgivesimplementationofvariousservice()methods
ofServletinterface.
Tocreateaservlet,weshouldcreateaclassthatextendsHttpServletabstractclass.TheServlet
classthatwewillcreate,mustnotoverrideservice()method.Ourservletclasswilloverrideonlythe
doGet()and/ordoPost()methods.
Theservice()methodofHttpServletclasslistenstotheHttpmethods(GET,POSTetc)fromrequest
streamandinvokesdoGet()ordoPost()methodsbasedonHttpMethodtype.
HTTP Servlet Class
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14. UNIT -III : Servlet
WebcontainerisresponsibleformanagingexecutionofservletsandJSPpagesforJavaEE
application.
Whenarequestcomesinforaservlet,theserverhandstherequesttotheWebContainer.Web
Containerisresponsibleforinstantiatingtheservletorcreatinganewthreadtohandletherequest.
ItsthejobofWebContainertogettherequestandresponsetotheservlet.Thecontainercreates
multiplethreadstoprocessmultiplerequeststoasingleservlet.
Servletsdon'thaveamain()method.WebContainermanagesthelifecycleofaServletinstance.
How a Servlet Application Works
14

15. UNIT -III : Servlet
ServletscanbeusedforhandlingboththeGETRequestsandthePOSTRequests.TheHttpServlet
classisusedforhandlingHTTPGETRequestsasithassomespecializedmethodsthatcan
efficientlyhandletheHTTPrequests.
Thesemethodsare:
doGet(),
doPost(),
doPut(),
doDelete,etc
Handling HTTP request & Responses
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16. UNIT -III : Servlet
<html><body>
<formaction="numServlet">
selecttheNumber:
<selectname="number"size="3">
<optionvalue="one">One</option>
<optionvalue="Two">Two</option>
<optionvalue="Three">Three</option>
</select>
<inputtype="submit">
</body></html>
Handling HTTP request & Responses
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17. UNIT -III : Servlet
Handling HTTP request & Responses
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18. TheServletRequestclassincludesmethodsthatallowyoutoreadthenamesandvaluesof
parametersthatareincludedinaclientrequest.Wewilldevelopaservletthatillustratestheir
use.Theexamplecontainstwofiles.
A Web page is defined insum.htmland a servlet is defined inAdd.java
<html><body><center>
<form name="Form1" method="post" action="Add">
<table><tr><td><B>Enter First Number</td>
<td><input type=textbox name="Enter First Number" size="25" value=""></td>
</tr>
<tr><td><B>Enter Second Number</td>
<td><input type=textbox name="Enter Second Number" size="25" value=""></td>
</tr></table>
<input type=submit value="Submit“></body></html>
UNIT -III : Servlet
Reading Servlet Parameters

19. import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Add
extends HttpServlet
{
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
// Get print writer.
response.getContentType("text/html");
PrintWriter pw = response.getWriter();
// Get enumeration of parameter names.
Enumeration e = request.getParameterNames();
// Display parameter names and values.
int sum=0;
UNIT -III : Servlet
Handling HTTP request & Responses

20. while(e.hasMoreElements())
{
String pname = (String)e.nextElement();
pw.print(pname + " = ");
String pvalue = request.getParameter(pname);
sum+=Integer.parseInt(pvalue);
pw.println(pvalue);
}
pw.println("Sum = "+sum);
pw.close(); } }
UNIT -III : Servlet
Handling HTTP request & Responses

21. •ThesourcecodeforAdd.javacontainsdoPost()methodisoverriddentoprocessclientrequests.
•ThegetParameterNames()methodreturnsanenumerationoftheparameternames.Theseare
processedinaloop.
•We can see that the parameter name and value are output to the client. The parameter value is
obtained via the getParameter( ) method.
URL : http://localhost:8080/servlets/sum.html
UNIT -III : Servlet
Handling HTTP request & Responses

22. UNIT III: Servlet
Reference
22
BookDetails:
TEXTBOOKS:
1.WebTechnologies,UttamKRoy,OxfordUniversityPress
2.TheCompleteReferencePHP–StevenHolzner,TataMcGraw-Hill
REFERENCEBOOKS:
1.WebProgramming,buildinginternetapplications,ChrisBates2ndedition,WileyDreamtech
2.JavaServerPages–HansBergsten,SPDO’Reilly
3.JavaScript,D.Flanagan,O’Reilly,SPD.
4.BeginningWebProgramming-JonDuckettWROX.
5.ProgrammingWorldWideWeb,R.W.Sebesta,FourthEdition,Pearson.
6.InternetandWorldWideWeb–Howtoprogram,DietelandNieto,Pearson.

23. UNIT III : Servlet
Video Reference
23
Video Link details (NPTEL, YOUTUBE Lectures and etc.)
➢https://nptel.ac.in/content/storage2/nptel_data3/html/mhrd/ict/text/106106093/lec39.pdf
➢http://www.nptelvideos.in/2012/11/internet-technologies.html
➢https://nptel.ac.in/courses/106105191/

24. UNIT III : Servlet
Courses
24
courses available on <www.coursera.org>, andhttp://neat.aicte-india.org
https://www.coursera.org/
Course1:WebApplicationsforEverybodySpecialization
Builddynamicdatabase-backedwebsites..UsePHP,MySQL,jQuery,andHandlebarstobuildweb
anddatabaseapplications.
Course2:JavaProgramming:SolvingProblemswithSoftware
LearntoDesignandCreateWebsites.Buildaresponsiveandaccessiblewebportfoliousing
HTML5,JavaServlet,XML,CSS3,andJavaScript

25. UNIT-III : Servlet Programming
Tutorial Topic
25
Tutorial topic wise
➢www.geeksforgeeks.org › introduction-java-servlets
➢www.edureka.co › blog › java-servlets
➢beginnersbook.com › servlet-tutorial
➢www.tutorialspoint.com › servlets
➢www.javatpoint.com › servlet-tutorial

26. UNIT-III : Servlet
Multiple Choice Questions
26
Servlet–MCQs
1.WhichofthefollowingcodeisusedtogetanattributeinaHTTPSessionobjectinservlets?
A.session.getAttribute(Stringname) B.session.alterAttribute(Stringname)
C.session.updateAttribute(Stringname) D.session.setAttribute(Stringname)
2.WhichmethodisusedtospecifybeforeanylinesthatusesthePintWriter?
A.setPageType()B.setContextType()
C.setContentType() D.setResponseType()
3.WhatarethefunctionsofServletcontainer?
A.Lifecyclemanagement B.Communicationsupport
C.Multithreadingsupport D.Alloftheabove
4.Whatisbytecode?
A.Machine-specificcode B.Javacode
C.Machine-independentcode D.Noneofthementioned
5.WhichobjectofHttpSessioncanbeusedtoviewandmanipulateinformationabouta
session?
A.sessionidentifier B.creationtime
C.lastaccessedtime D.Allmentionedabove

27. UNIT-III : Servlet
Servlet-Tutorial Problems
27
Servlet –Tutorial Problems:
1.Write a Servlet program to read employee details
2.Write a Servlet program to uploads files to remote directory

28. UNIT-III : Servlet
Question Bank
28
PHP –universities & Important Questions:
1.Defineasessiontrackerthattracksthenumberofaccessesandlastaccessdataofa
particularwebpage.
2.WhatisthesecurityissuesrelatedtoServlets.
3.ExplainhowHTTPPOSTrequestisprocessedusingServlets
4.Explainhowcookiesareusedforsessiontracking?
5.ExplainaboutTomcatwebserver.
6.WhatisServlet?ExplainlifecycleofaServlet?
7.WhataretheadvantagesofServletsoverCGI
8.Whatissessiontracking?Explaindifferentmechanismsofsessiontracking?
9.WhatisthedifferencebetweenServletsandapplets?
10.WhatisthedifferencebetweendoGet()anddoPost()?

29. Thank you
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