servlets.ppt

8/16/2019 Servlets.ppt

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Servlets, Sessions,Servlets, Sessions,

and Cookiesand CookiesLecture 8Lecture 8cs193i – Internetcs193i – Internet

TechnologiesTechnologiesSummer 2004Summer 2004

Stanford UniversityStanford University


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Administrative Stuf Administrative Stuf

H !3 due "ugust 2H !3 due "ugust 2

#a$ !3 due "ugust 4#a$ !3 due "ugust 4

#ocal S%&' students must ta(e )nal#ocal S%&' students must ta(e )nalon*cam+uson*cam+us


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Cookies and Privacy Cookies and Privacy

%oo(ies are good%oo(ies are good ,emem$er -ho you are and your,emem$er -ho you are and your

+references+references

Session trac(ingSession trac(ing

%oo(ies are $ad%oo(ies are $ad hen develo+er is not carefulhen develo+er is not careful

.store +ass-ord/ credit card info/ etc.store +ass-ord/ credit card info/ etc hen +eo+le a$use themhen +eo+le a$use them

.trac( information a$out you.trac( information a$out you


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The Big PictureThe Big Picture

a(ing e$ "++lications etter

or the 'evelo+er

ore features/ $etter "&I/ 555 Time*To*ar(et .$eat your com+etitors

or the 6nd*User

etter %ontinuity etter User 67+erience


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Why Java Servlets nstead Why Java Servlets nstead

o! C"#o! C"# 68icient/ %onvenient/ &o-erful/

&orta$le/ Secure/ Ine7+ensive #ight-eight threads instead of S threads

created Single co+y of code $rought into memory

for all threads versus +er thread 'ata .session state can $e stored across

threads -ithin servlet container :ava is +orta$le and secure ,e;uires little e7+ense once servlet

container integrated -ith -e$ server


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Servlet StructureServlet Structure

:ava Servlet $


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We$ A%% &ith Servlets We$ A%% &ith Servlets

HEADERS

BODY

Servlet

doGet()

…

…

GET …

Servlet Container


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' Sim%le Ste%s !or Java' Sim%le Ste%s !or Java

ServletsServlets15 Su$class o8 Htt+Servlet

25 verride do?et.5555 method

35 Htt+Servlet,e;uest get&arameter.@+aramAame@

45 Htt+Servlet,es+onse set %ontent Ty+e

get &rintriter send te7t to client via &rintriter

B5 'onCt use instance varia$les


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Servlet(JSP Container Servlet(JSP Container

:ava Servlet 254

:avaServer &ages 250

Tomcat is the $asis for the o8icial

reference im+lementation


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)elloWorld*+ava)elloWorld*+ava

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class HelloWorldExample extends HttpServlet {

public void doGet(HttpServletReuest reuest!

HttpServletResponse response" thro#s $%Exception! ServletException

{

response.set&ontent'pe()texthtml)";

+rintWriter out , response.-etWriter(";

out.println()html/)";

out.println()head/)";

out.println()title/Hello World0title/)"; out.println()head/)";

out.println()bod b-color,1)#hite1)/)";

out.println()h2/Hello World0h2/)";

out.println()bod/)";

out.println()html/)";

3

3


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import java.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class ReuestHeaderExample extends HttpServlet {

public void doGet(HttpServletReuest reuest! HttpServletResponse response"

thro#s $%Exception! ServletException

{

response.set&ontent'pe()texthtml)";

+rintWriter out , response.-etWriter(";

Enumeration e , reuest.-etHeader4ames(";

#hile (e.has5oreElements("" {

Strin- name , (Strin-"e.nextElement(";

Strin- value , reuest.-etHeader(header4ame";

out.println(name 6 7 , 7 6 value ";

3

3

3

e-uest)eader./am%le*+e-uest)eader./am%le*+

avaava


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Servlet Li!ecycleServlet Li!ecycle

0Creation10Creation1 Single instance created

init. method called

Dou can override init. in yoursu$class of Htt+Servlet to do someinitial code5555

init. is AT called again on furtherre;uests


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0Service 2ethod10Service 2ethod1 n each re;uest/ the server s+a-ns

a ne- thread and calls service.

service. chec(s HTT& re;uest ty+eand calls a++ro+riate doEEEE .?et/&ost/ &ut555

donCt override service .unless youreally (no- -hat youCre doing


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0do"et01, doPost0110do"et01, doPost011 ,eal meat of the -e$ a++ is here

do&ost. can call do?et./ or viceversa

no doHead.555 system uses headersof do?et. result


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0destroy0110destroy011 or some reason .servlet idle/ etc

the server may -ant to remove theservlet from memory

destroy. allo-s you to close 'connections/ -ra+ u+/ etc555

'onCt count on destroy to -rite+ersistent state .server may crash$efore you ever get hereF


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Accessing e-uest Accessing e-uest

Com%onentsCom%onents get&arameter.@+aram1@

get%oo(ies. G %oo(ieJ

get%ontent#ength. get%ontentTy+e.

getHeaderAames.

getethod.


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.nvironment 3aria$les.nvironment 3aria$les

:avaServlets do not re;uire you to use :avaServlets do not re;uire you to use

the clun(y environment varia$les usedthe clun(y environment varia$les used

in %?Iin %?I

Individual functionsKIndividual functionsK &"THLIA&"THLIA re;5get&athInfo.re;5get&athInfo.

,6T6LHST,6T6LHST re;5get,emoteHost.re;5get,emoteHost.

MU6,DLST,IA?MU6,DLST,IA? re;5getMueryString.re;5getMueryString.


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Setting es%onseSetting es%onse

Com%onentsCom%onents Set status )rstF

setStatus.int

Htt+Servlet,es+onse5S%LN555 send6rror.int/ String send,edirect.String url


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Setting es%onseSetting es%onse

Com%onentsCom%onents Set headers

setHeader.

set%ontentTy+e.Ote7t=htmlP

ut+ut $ody &rintriter out G res+onse5getriter.Q

out5+rintln.@RHT#RH6"'555@


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J4.. AP J4.. AP

htt+K==


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5evelo%ing Servlets5evelo%ing Servlets

0Start &( $a$y ste%s10Start &( $a$y ste%s1 Install TomcatInstall Tomcat

,un Tomcat,un Tomcat

,un e7am+les,un e7am+les


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Creating 6our 7&nCreating 6our 7&n

ServletServlet rite ne- servlet .e5g5 Hi5


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5e$ugging5e$ugging

use out5+rintln to the html

+rint to a soc(et on localhost555


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ive 2inuteive 2inute

Break Break


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Continuity Pro$lemContinuity Pro$lem

SessionK " user sits do-n/ enters a-e$site/ does some -or(/ e7its

HTT& Stateless 'oes Nee+*"live Hel+


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Client vs* Server SideClient vs* Server Side

%lient Side Store aria$leGalue indings in HT#

&age/ or %oo(ies

Server Side Store aria$leGalue indings in

'=Server emory

Store Session I' on %lient Side/ toidentify %lient


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Three Ty%ical SolutionsThree Ty%ical Solutions

%oo(ies

U,# ,e-riting

Hidden ields


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)TTP Cookies "ra$9$ag)TTP Cookies "ra$9$ag

#ifetime#ifetime Session – not -ritten to )le systemSession – not -ritten to )le system

&ersistent – -ritten to user +references&ersistent – -ritten to user +references

nly returns coo(ie to re;uestingnly returns coo(ie to re;uesting

domaindomain

%oo(ie must $e s+eci)ed $y content%oo(ie must $e s+eci)ed $y content

Ao s+ecial characters in coo(ieAo s+ecial characters in coo(ie


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)TTP Cookies)TTP Cookies

Strin- s$8 , ma9e:niueStrin-(";

Hashtable session$no , ne# Hashtable(";

Hashtable -lobal'able , ind'ableStorin-Sessions(";

-lobal'able.put(s$8! session$no";

&oo9ie session&oo9ie , ne# &oo9ie()


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%n reuest

Strin- s$8 , reuest.-et&oo9ie()


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%n reuest



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%n reuest



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n9Bro&ser Cookien9Bro&ser Cookie

2anagement2anagement


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:L e&riting:L e&riting

,e-rite all U,#s in res+onse to containSessionI' htt+K==foo5com=servlet=cartidG1237yV

&arse out session I' from re;uest line

encodeU,#. in Htt+,es+onse o$


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:L e&riting:L e&riting


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)idden orm ields)idden orm ields

Rin+ut ty+eGOhiddenP nameGOsessionP valueGO555P


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Java Servlet Solution Java Servlet Solution

Session trac(ing "&I $uilt on to+ ofU,# re-riting or coo(ies #oo( u+ Htt+Session o$


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Look u% Session n!oLook u% Session n!o

HttpSession session , reuest.-etSession(true";

Shoppin-&art sc , (Shoppin-&art"

session.-et=ttribute()shoppin-&art)";

i (cart ,, null" {

cart , ne# Shoppin-&art(";session.set=ttribute()shoppin-&art)! cart";

3

...

do somethin- #ith our shoppin- cart object


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)tt%Session 2ethods)tt%Session 2ethods

+u$lic String getId.

+u$lic $oolean isAe-.

+u$lic long get%reationTime.

+u$lic long get#ast"ccessedTime.

+u$lic int geta7InactiveInterval.

+u$lic void seta7InactiveInterval.intsecs

+u$lic void invalidate.


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Associate n!o &( Session Associate n!o &( Session

HttpSession session , reuest.-etSession(true";

session.set=ttribute()reerrin-+a-e)!

reuest.-etHeader()Reerer)"";

Shoppin-&art cart ,

(Shoppin-&art"session.-et=ttribute()previous$tems)";

i (cart ,, null" {

cart , ne# Shoppin-&art(";

session.set=ttribute()previous$tems)! cart";

3

Strin- item$8 , reuest.-et+arameter()item$8)";

i (item$8 0, null" {

cart.add$tem(&atalo-.-et$tem(item$8"";

3


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Session TerminationSession Termination

"utomaticF "fter a long enoughinterval .geta7InactiveInterval


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Session TrackingSession Tracking

Amazon

Servlet Container

Session ID = !"#Y$

S%o&&in' Cart s

item ="!*+

$e%&e't


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Amazon

Servlet Container

Session ID = !"#Y$

S%o&&in' Cart s

item ="!*+

$e'!o('e:

Set-Cookie: 'i)=123*+,


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Amazon

Servlet Container

Session ID = !"#Y$

S%o&&in' Cart s

item ="!*+

$e%&e't:



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Amazon

Servlet Container

Session ID = !"#Y$

S%o&&in' Cart s

item ="!*

item !=,+

$e%&e't:


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