natraj servlet2015

8/17/2019 Natraj Servlet2015

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2015-04-10

Normal java application will be executed manually from command

prompts. Whenever there is a need.

The web resource program of web application will be executed by web

server software dynamically whenever request is given to those web

resource programs. From client nothing but browser window, this

indicates web resource programs will not be executed manually they

will be executed dynamically by webserver software like tomcat.

Web server s/w automates web application and its web resource

program execution.

It listens to client request passes them to web resource program

execute web resource program gather output form web resource

programsends that output to client (browsers) as response in the

form of web pages.

E.g. Tomcat, IIS, AWS AND etc….

IIS-internet information service

AWS — Apache web server


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The process of keeping developed web application in web server is

called deployment and reverse is called un-deployment.

With

respect to

diagram

(1) Browser

gives

request to web application(2) Webserver listen client requests continuously take the request and

passes the request to appropriate web resource program (like servlet

program)

(3) The web resource program in web application executes

dynamically

(4) If needed, the web resource program interacts with database s/w.(5) The output generated by the web resources programs gives to web

server.

(6) Webserver sends output to browser as response in the form of web

page.

In one web application we can have one or more web resource

program.

In one web application we can deployed one or more web

application (web sites)


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We can develop web application as two tier application( without

database software or as three tier application (with database s/w)

When web application developed as two tier application it looks

like thin client-fat server application

2015-04-13

Based on content they generate there are two types of web resource

1. Static web resource programs(Generate static web program)

2. Dynamic web resource program (generate dynamic web program)

Based on the place where web resource program execute there are twotypes of web resource program

1.

Server side web resource program

These program executes in web server itself when request is given

Eg servlet program, jsp program end etc.

2. Client side web resource program

These programs go to browser window from web server for execution

when requested.

Eg- html program, javascript program and etc.


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Note: Generally all dynamic web resource programs are server side web

resource program and static web resource program are client side web

resource program.

Note: Decide whether web resource program are server side or not

based on the location where they execute, not based on the location

where they reside.

List of browser s/w

IE from micro soft

Navigator --> Netscape

Safari -Apple

FirefoxMozilla

Hot Java Red Hat

Chromefrom Google (1)

Operafrom Opera soft

List of server side web technology to develop server side web resource

program

ServletsFrom sun Ms(oracle corp) (java)(1)

Jsp “From sun Ms(oracle corp) (java)(2)

(Non-java)Asp----from Microsoft

Asp.net - from Microsoft (3)

Asp.net MVC-from Microsoft (2)

SSJS----------from Netscape (server side java script)


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PHP--------from Apache (4)

ColdFusion----- from Adobe.

List of client side technology ( to develop client side web resource

programs)

Html from W3C

Java scriptfrom Netscape + sun Ms

VB script from Micro Soft

Ajax -- from Adaptive path

Jquery

DOJO

AngularJS

And etc

List of Webserver s/ws

Tomcat ---------- from Apache (java) (1)

JWS ------------ from Sun microsystem (java)

Resin---------- from Resin soft (java) (4)

Jetty---------- from Adobe (java)

IIS --------From Microsoft (non-java)(2)

PWS---------from Microsoft (non- java)

AWS------- from Apache (non-java) (3) NFTS(Netscape first track server) from Netscape

Etc ………

List of Application server software


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It is enhancement of web server software.

Weblogic--from BEA systems (oracle corporation) (1)

Websphere -- form IBM(3)

GlassFish --- from sun Microsoft(2)

Jboss----- from Apache(RedHat)(4)

Oracle10g IAS -- from Oracle Corporation

Jrun----------from Adobe

PAS-------- FROM Pramathi soft

(PAS:Pramathi Application server)

List of DB s/w

Oracle ---- from oracle corporation

DB2-----from IBM

SQL Serverfrom Micro Soft

Post greSQLEnterprise DB

Mysql-devx (sunms) (oracle oracle)

2015-04-14

To execute applet we need applet program we need applet viewer or

applet container.

To execute html program we need html interpreter.

To execute servlet program we need servlet container

To execute jsp program we need jsp container.


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Both servlet container and jsp container internally uses

jvm/jre.

Applet viewer also internally uses jvm/jre.

Every servlet program is a java class having code to process

request and to generate response.

We need not to arrange servlet container separately, they

come automatically along with web server s/w installation

(java based)

What is container?

Container is s/w program /application that takes care of whole

life cycle of given resource (birth to death) (object creation to

object destruction)

Servlet container takes care of servlet program life cycle and

jsp container takes care of jsp program life cycle.Container is like aquarium taking care of the whole life cycle

of given fishes.

(web resource programs)

The additional, optional and configurable (allows enabling or

disabling) logics on our apps to make our application more

perfect are called middleware services. These are not main


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logics in application development. These are additional and

optional logics to apply on our applications..

When servlet program is requested it goes to servlet container

for execution.

jsp container internally uses the support of servlet container

Tomcat

Type: java based web server.

Version :8.x(compatible with jdk 1.7+)

7.x (compatible with jdk 1.6+)

Vendor: Apache

Open source s/w (free ware)

Default port no: 8080

Creator : Mr. David Doncuson

Servlet container: CATALINA

Jsp container: JASPER

To download s/w apache-tomcat-7.8.exe from www.apache.org


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2015-04-15

While installing Tomcat server we need to supply the following details;

a) Jre location

b) http port no:2525 (default 8080)

c) Tomcat installation folder:D:\Tomcat8.0()

d) Administration details: UserName: admin

Password: admin

Note: install in other than c:

To start Tomcat Server:

Go\bin directory use tomcat8.exe file

When server is started one daemon process will be created listening to

client request continuously.

To see home page of Tomcat

In browser window type url

Http://localhost:2525 (host name and port no of tomcat)

To Change port number of Tomcat after installation

Go TO \conf\server.xml file and modify the “port”

attribute value of first tag and restart the server.

Understanding installation Directories of Tomcat

D:\Tomcat8.0

|-bin

http://http//localhost:2525%20%20%20(hosthttp://http//localhost:2525%20%20%20(hosthttp://http//localhost:2525%20%20%20(host


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|*.exe (tomcat8.exe), *.bat (startup.bat ,shutdown.bat)

|conf

|-*,xml(server.xml( server.xml, tomcat-users.xml,….)

|lib

|-*.jar(servlet-api.jar, jsp-api.jar, catalina.jar, jasper.jar,….)

|-logs

|*.txt files

|webapps

|dir1, dir2,…….

|*.war files|temp

|misc files

To deploy all java web application in tomcat server we can place them

in \webapps folder either in the form of directors or

war files.

War files: web application archieve. \lib\servlet_api.jar represents servlet api (pkgs)

Jsp_api.jar represents jsp api (pkgs)

Catalinar.jar represents (servlet container)

Jasper.jar represents (jsp container)

Web container = servlet container + jsp container..

Responsibilities of web server

Takes request from client by listening client request continuously for

this it start Daemon process.


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Passes the request to container for request processing

Provides containers (like servlet/jsp containers) to execute server side

program.

Provides middleware services(like security)

Provides environment to automate. The web application and its web

resource program execution.

Provides environment to deploy, un-deploy, start, stop and reload web

application.

Takes results from container and sends them to browser window as

responses.

Sends the code of client side web resource program to browser window

for execution and etc……

Responsibility of containers:-

Takes request form web server and executes server side web

resource program dynamically.

Takes care of server side porg life cycle birth to death.

Takes care of communication between web resource progs.

Performs various activities related to request handling and response

generation.

Type of containers


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url, uri,urn

2015-04-16

Servlet, jsp, ejb, jms and etc jee module technologies.

Technology is not installable s/w because they just give rules and

guideline to develop s/w. These s/w are installable working with these

s/w are nothing but working with technology.

Web server /application server s/ws are given based on jee technologies

Installing.

This server s/w and working with these server s/w is nothing but

working with JEE module.

Eg. Installing tomcat, web logic s/w and using them is nothing but

JEE module

Based on the technology we use there are following container:

a) Servlet container:Based on Servlet Technology

b) Jsp container: Based on JSp technology.

c) EJB container Based on EBJ Technology.

Based on physical existence of container with respect to server there are

3 type of containers

a)

Standalone container

Here server and container together comes as single piece of program

b) In-Process container :


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Here container inside the server as separate piece of code Servlet

container /jsp container of Tomcat Server is called In-Process

container.

c)

Out-Process container:

Here container resides outside server but will be attached to server

externally the servlet /jsp container attached with IIS server

externally is called Out-Process container.

Thread is a sub-process or light weight process.

Transferring control between process or threads through scheduling is

called context switching or control jumping this takes more time for

process and less time for threads.

When we start the execution of java application one process will be

started having two default threads (main thread, garbage collector

thread).


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Server side web technologies


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If multiple request given to servlet program (thread based server side

technology ) then the servlet container creates only one object of our

servlet class but starts multiple threads on that object for multiple

request since control jumping between thread takes less time the

performance of web application will be good even though number of

request are increase or decrease this makes our web application as

scalable


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2015-04-17

Definition of servlet

Servlet is java based server side web technology to develop dynamic web1.

resource program or component having capability to generate dynamic

web pages.

Servlet is java based web technology whose web resource program can2.

extend the functionality of web server or Http server.

Servlet is java based technology that allows to develop single instance3.

multiple threads based server side web component in java web application

having the capability to generate dynamic web pages(Refer pervious

diagram)

Servlet is a JEE module technology/specification that gives api for vendor4.

companies as rules and guideline to develop servlet container s/w (part of

webserver s/w) and also gives same api for programmer to develop server

side/dynamic web resource program in java web applications

Note: Every Servlet program is java class using api. The whole life cycle of

this java class will be taken care by Servlet Container birth (object creation)to Death(object destruction))

For various features of servlet refer page no:- 80,82

For basic of servlet container refer page 76 to 82.


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In tomcat server \lib\lib\servlet-api.jar file

represents servlet API.

Three import re

2015-04-17

There are three way to develop servlet component/program.

Approach-1) Take a class implementing javax.servlet.Servlet(I) and

provide implementation for all the 5 methods of that interface.Limitation: Providing implementation to 5 methods even though

there is no need is always complex.


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In our servlet class we place logic to process request and logic to

generate response in the service(-,-) method. This response goes to

browser window as webpage.

Approach-2) take class extending from

javax.servlet.GenericServlet(AC) and provide implementation for

service(-,-) method.

Limitation: We cannot work with all the features of protocol http

because GenericServlet is not any specific protocol.

GenericServlet allows to work with all protocols but does not allow

to use any protocol for 100%.

Approach-3) Take a class extending from

javax.servlet.http.HttpServelt(AC) and override 1 of the 7 doxxx(-,-)

methods and 1 of 2 service(-,-) methods.

Note: this best approach to develop servlet prog because it allows to

us to use all the features of protocol “http”.

Servlet container recognized as java pro as servlet porg only when it

implments javax.servlet.Servlet(I) directly or indirectly.

How many type of servlets ?

There is possibility of developing ―n‖ types of servlets like Http servlet,

ftp servlet, smtp servlet and etc….but we prefer developing servlet as

http servlet because entire web/internet and server are designed based

on protocol “http”.

GenericServlet is not a separate type of servlet. It is a common super

class multiple protocol specific servlet classes. As of now there is only

sub class for GenericServlet that is “HttpServlet”.


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Web application is collection of web resource prog like servlet, jsp,

html prog having capability to generate web pages. Web application

also contain some helper resources like image, audio, video files and

etc.. These programs cannot generate web pages but they help other

program towards generating web pages.

Jvm beings application execution with main method so we place main

method in java application.

Servlet container executes our servlet program. This container

call service(-,-) method of servlet prog to process the request, so

we place service(-,-) method in servlet program having request

processing logic and response generation logic.

first java web application Development having Servlet prog as web resource

program.

-----------------------------------------------------------------------------

-------------------------------------------------------------------

Step-1) Create Deployment directory structure of web application.


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This Deployment directory structure is packing mechanism of keeping

web resource prgs in java web application.

This structure is common in all server and not specific any server. Thisis designed by sun ms as part of server specific, so all server recognizes

the directory structure based web application deployment.

The web root folder name is user defined, after deployment this

name is become name of the web application.

Step-2) develop the servlet prog(DateSrv.java)

*************pmd plugin************

[email protected]

2015-04-10

Our servlet class(DateSrv) hierarchy is javax.servlet.Servlet Interface

javax.servlet.Servlet

^

| implements

Javax.servlet.GenericServlet(AC)

mailto:[email protected]:[email protected]


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^

| extends

Com.nt.DateSrv(c )

Our servlet program class must be taken as public to make our class

ready for instantiation through SevletContainer because only public

classes are visible outside the container.

Servlet container create object of our servlet class and calls service

methods on that object to process the request.

For every request given to servlet program servlet container create one

additional set of object request, response object and these objects are

visible in our servlet porg as the parameter service(-,-) methods.

In service(-,-) method we use request object to gather data that comes

along with the browser generated request and response object is useful

to send output to browser through web server.

Res.setConentType(“text/html”) gives instruction to browser through

web server to display received contend as html code based textdocument.(webpage)

PrintWriter pw=res.getWriter(); use access to PrintWriter object that is

there in response object i.e we get PrintWriter stream objet that points

to response object to destination.


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Pw.println(“ Hello”);

This method writes given msg( hello) to response object,

response object writes that msessage to webserver. Webserver writes

this message to browser as the content of webpage.

pw.close() closes the PrintWriter Stream that mean we cannot write

further content to response object form servlet program. This is

nothing but committing the response.

Step:3) our servlet program is using servlet api, But is not part of jdk.

Tomcat server gives servlet-api.jar having servlet api, so add that file

to classpath.

Mycomputerpropertiesadv systemsettingenv

variablesuser/system variablevariable name

Variable name=classpath

value: D:\Tomcat 8.0\lib\servlet-api.jar;.

(ok)

Step:4)compile the servlet prog (DatSrv.java) E:\Javaprogramming\ServletN\DateApp\WEB-INF\classes

Step:5) configure servelt prog in web.xml file

Passing details of servlet program in web.xml file to make servlet

container recognizing ther servlet prog is called servlet pro

configuration. Based this cfg only servlet container locates servlet

prg that is there in WEB-INF\classes folder of web application.

abc--abc is logical name


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com.nt.DateSrv--

com.nt.DateSrv is fully --qualified name acting serlet

programming

abc--abc must match with

above

--every servlet programmg is identified with its url-pattern to

generate --request

--it is not identified with its logical name or its real class name

-- all the servlet prog web application must be cfg in web.xml

file so it is called web application cfg file.

-- the moment we deploy web application in webserver the servlet

container reads the web.xml file, so it is also called deployment

descriptor file(DD file)

Step6) start tomcat web server

User\bin\tomcat8.exe file

Step7) deploy the web application (DateApp)

Copy e:\DateApp folder to \web app

Step8) talks about deployment of web application

Step9) Test the web application

Request url in browser window: http://localhost:3030/DateApp/test1

http://localhost:3030/DateApp/test1http://localhost:3030/DateApp/test1http://localhost:3030/DateApp/test1http://localhost:3030/DateApp/test1


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Htttp: is protocol.

localhost:3030 host name and port name

test1 is url pattern of servlet

2015-04-22

The modification done in servlet program of deployed web applicationwill be reflected only after recompilation of servlet prog and reloading

of web application.

For recomplication

D:\Tomcat8.0\web apps\DateApp\WEB-INF\classes>javac – d .

DatgeSrv.java

For reloading

page-Manager appusername:admin and

password:adminsubmit

Tomcat web application manager window DateAppreload

The message of system.out.println(_) goes to server console as log

messages/confirmation messages.

The messages of pw.println() goes to browser window as the content of

web page.

ServletContainer instantiate our servlet prog calss obj by using 0-

param constructor so we must make sure that 0-parameter constructor

is available in our servlet porg directly(*1) or indirectly(*2).


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*1 placed by the programmer manually.

*2Defaut 0-parameter constructor generated by the javac compiler

implicitly.

Can we place only parameterized constructor in our servlet class?

As) NO

Because ServletContainer creates our servlet class object using

0_paramer constructor.


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With respect to diagram.

1) Programmer deploys “Dateapp” web application in Tomcat webserver

2)

The ServletContainer of Tomcat reads, verifies web.xml file and stores the

content of web.xml at RAM level in HashMap as in-memory

MetaData.(The information like servlet program details and other more

details.)

3) End user gives request to servlet program by typing request url in the

browser address bar.

4) Based on “localhost:3030” of request url the request goes to Tomcat

server.5) Based on “DateApp” of request url the Tomcat passes the request to the

deployed “DateApp” web application.

6) Based on “/test1” of request url the servlet container gets logical name

(abc), class name(com.nt.DateSrv) from in memory MetaData.

7) ServletContainer create 1 set of request, response object for current

request.8) ServletContainer loads “com.nt.DateSrv” class from WEB-INF\classes

folder for object creation and completes all initialization formalaties.

9) ServletContainer calls service(-,-) on DateSrc class object having req, res

object as the arguments.

10) Service(-,-) processes the reque4st and sends the generated output to

browser as response through web server to display in the form dynamic webpage.

-> servlet program is not identified with its class name because if class name is

exposed in request url that make idea to hackers regarding the technology used


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in web site development.

To avoid this problem url pattern is introduced to hide servlet class name from

end users. This also gives chance to have multiple url pattern one servlet

program. (Palce multiple tags under tage for

this)

Example:

abc

/nit.c

/abc/xyz/nit.cpp

Requested urls: http://localhost:3030/DateApp/nit.c

http://localhost:3030/DateApp/abc/xyz/nit.cpp

2015-04-23

Fgdgfd

The modification done in web.xml file will be recognized by

understanding servlet container automatically because it internally

reloads the web application.

When server stopped or when web application is stopped/reloaded all

the existing object ( our servlet class object, request, response) object

and etc) will be destroyed.

Reloading web application is nothing but (stopping web application

)+(starting web application)

http://localhost:3030/DateApp/nit.chttp://localhost:3030/DateApp/nit.chttp://localhost:3030/DateApp/abc/xyz/nit.cpphttp://localhost:3030/DateApp/abc/xyz/nit.cpphttp://localhost:3030/DateApp/abc/xyz/nit.cpphttp://localhost:3030/DateApp/nit.c


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our porg is single instance multiple threads component that is if our

servlet prog get 10 requests from same or different clients (browser

windows) then

a)

Servlet Container creates only object of our servlet prog class.

b) Servlet container creates 10 threads representing 10 request on our

servlet class object.

c) Servlet container creates 10 sets of request, response object for 10

responses on 1 set per request basis.

To demonstrate above diagram practically place following code in

service method of servlet program in as shown below.

try{

}

catch(Exception e){

}

pw.println("
hascode of request obj"+req.hashCode());


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pw.println("
hascode of response obj"+res.hashCode());

pw.println("
hascode of our servlet class

object"+this.hashCode());

pw.println("
hascode of current threadobj"+Thread.currentThread.hashCode());

For every object jvm gives one unique value that is hashcode. To get

this hashcode value use objref.hashCode() (method belong to

java.lang.Object class)

For every request given to web resource program the servlet container

creates 1 thread and 1 set of request, response objects represent that

request and same will be destroyed once request related response goes

to browser from server.

In some servers if more (huge) request are given to servlet program the

servlet container may create more than one object to our servlet

container.( it is exceptional case.)

Javax.servlet.ServletRequest(I)

extends

Javax.servlet.http.httpServletRequest(I)

Javax.servlet.ServletResponse(I)


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extends

Javax.servlet.httpServletResponse(I)

Q) How can we say request, response are objects when ServletRequest,ServletResponse are interface?

Ans) _ request object means it is the object of underlying servlet container

supplied java class that implements javax.servelt.ServletRequest(I) directly or

indirectly.

response object means it is the object of underlying servlet container supplied by

java that implements javax.servlet.ServletResponse(I) directly or indirectly.

Programmers nerve expose these the class name of these objects in

their Servlet porg because the class names changes server to server or

container to container. This helps to develop servlet program as server

independent program(portable program)

Tomcat server request object class name

org.apache.catalina.connector.RequestFacade

And response object class name

org.apache.catalina.connector.ResponseFacade

Refer- /lib/catalina.jar file

2015-04-24

Generic servlet gives only service method that is


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public void service(servletRequest req, ServeltRespose res) throws SE ,

IOException

HttpServlet gives two method(-,-) methods

1st service(-,-) |public service (-,-) mehtods

2nd service(-,-) |protected service (-,-) methods

protected void service(HttpServletRequest req, HttpServletResponse res)

thrwos SE, IOException

ServletRequest and ServletResponse obj don‖t allow to use protocol

“http” features.

HttpServletRequest and HttpServletResponse object allow to use

protocol “http” feature.

If web application contains multiple servlet programs we must have

those entire prog web.xml file having unique url pattern logical names.

By specifying different continent type (mime type) in servlet porg by

using res setContentType(-) we can make browser window to display

web pages in different format.MIME:- Multipurpose intent mail extension

Ex:- text/html, application/mswork, app/vendor.ms-excel and etc.

To get these MIME types we can “regedit” tool.

StartregeditHKEY_CLASSES_ROOT choose extension to know mine type.

web application-2

Develop web application having multiple servlet prog to generate web

pages in different format?


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Step-1) creates deployment directory structure.

E:\MIME App

|----WEB-INF

|----classes

|web.xml|----*.java(4)

|----com.nt

|----HtmlSrv.class

|----ExcelSrv.class

|----WordSrv.class

|----XmlSrv.class

Develop the Servlet progs (refer application -1 of pages 102 to 106)

Step-3) ake sure that servlet-api .jar is placed in classpath.

Step-4) compile the servlet program

E:\MIMEApp\WEB-INF\classes> javac – d . *.java

Step-5) Develop web.xml having 4 servlet configuration refer page-

105,106

Step-6) Start Tomcat server.

Step-7) Deploy the web application

Copy E:\MIMEApp folder to \webapps

folder.

Step-8) Test the web application.

Request urls

http://localhost:3030/MIMEApp/hturl

http://localhost:3030/MIMEApp/wdurl

http://localhost:3030/MIMEApp/docurl


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http://localhost:3030/MIMEApp/exlurl

20-may-2015

For every request given to servlet program the servlet container creates

1 set of ServletRequest, ServletResponse object and calls service(-,-)

method of our servlet program having those object as the arguments.

Understanding partial flow of execution from request arrival to req

generation using the “dateapp” application

D: Tomcat 8.0

|webapps

|DateApp

|WEB-INF

|classes

|web.xml|DateSrv.jvaa

|com.nt

|DateSrv.class

web,xml


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abc

com.nt.DateSrv

abc

/test


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a) programmer deploys the “DateApp” web application in Tomcat server

b) Tomcat Server makes ServletContainer to verify web.xml entries, if they

are valid the ServletContainer reads web.xml entries and stores in Hash

Map obj at RAM in Memory MetaData.

c) End-user (visitor) gives request by typing request url in the browser‖s

address bar.

d) Based on localhost:3030” of request url the Tomcat server takes the request.


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e) Based on DateApp” of request url server passes the request to DateApp web

application.

f) Based on “/test” of request url the container uses web.xml‖s in memory

MetaData and get servlet class name “com.nt.DateSrv”.

g) Servlet container creates 1 set of ServletRequset, ServeletResponse obj for

current request.

h) ServeltContainer checks the availability of our servlet class object if not

Available (DateSrv obj) then it load DateSrv class to create object also

complete all the formalities of instantiation.

i)

Servlet Container calls service(-,-) of DateSrv having ServletRequest,ServletResponse object as arguments.

j)

The service(-,- ) method generates output goes to browser window through

we server and browser window displays that output as web page based on

the received continent tape.

Javax.servlet.ServletRequest(I)

extends

Javax.servlet.http.httpServletRequest(I)

Javax.servlet.ServletResponse(I)

extends


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Javax.servlet.http.httpServletResponse(I)

sunMicro system/oracle gives servlet api as common api for all the

vendor companies having lots of interfaces. Every vendor company

gives ServletContainer, jsp container having more implementation class

of servlet api interfaces. These implementation will change server to

server, so we never place these implementations classes in our servlet

program to make our servlet prog as server independent(WODA)


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21-May-15


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if 10 request are given to our servlet program then servlet container

a)

create 1 object of our servlet porg

b) statrt 10 thread on our servlet class object representing 10 request

c) create 10 set of request and response obj for 10 req on 1 set per

reqest basis.

To prove the above statement practically place the following code

with the service method of any servlet program and give multiple

req form multiple browser window simultaneously.

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

class DateApp implements HttpServlet

{

public void service(HttpServletRequest req,HttpServletResponse res) throws

ServletException,IOException

{//getPrintWriter object

PrintWriter pw=res.getWriter();

try

{

Thread.sleep(30000);

}

catch (Exception e)

{

e.printStackTrace();

}

pw.write("
our servlet class object hashcode"+this.hashcode());

pw.println("
req obj hash code "+req.hashCode());

pw.println("
res.hashcode"+res.hashCode());

pw.println("
current thread is "+Thread.currentThread().hashCode());


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{

}

Jvm gives unique identity value for every object to get that value

hashcode() method.

To access currently running thread use Thread.currentThread()

method.

MIME Type

Res.setContentType(-) method given instruction to browser window todisplay received in different format of webpages.

The content type/MIME Types are:-

Text/html application/msword, application/vmd,ms-excel, text/xml,

tesxt/plain and etc.

MIME: multi purpose internet Main Extension

To know MIME types we can use “regedit” tool of windows

Start — run — regedit — HKEY_CLASS_ROOT — choose MIME type.

Javax.servlet.http.HttpServlet(AC) is having two service(-,-) methods

1. 1st service(-,-) /public service(-,-) method

Public void service(ServletRequest req,ServletResponse res) throws SE,IOE

2. 2nd service / protected service(-,-) method

Protected void servce(HttpServletRequest req,HttpServetlResponse res)

throws SE,IOE

2nd servie (-,-) is recommended to use because it allows us to work with

the second feature of protocol “http”.


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Procedure to develop web having 4 servlet program generating 4

different format webpages.

Step-1) creates deployment directory structure.

E:\MIMEApp

|WEB-INF

|classes

|web.xml |HtmlSrv.java

|ExcelSrv.java

|WordSrv.java

|xmlSrv.java

|com.nt

|*.class(4)

Setp-2) Develop Servlet program of web application.

Refer-application 1 of 103 to 106

Note: ServletRequest and ServletResponse object doesn‖t allow workingwith protocol http.

Note :-HttpServletRequest and HttpServletResponse obj allow us to

work with protocol “http” feature.

Step-3) compile the source code of the servlet program

E:\MIMEApp\WEB-INF\classes>javac – d . *.java

Step-4) develop web.xml file having 4 servlet program configurations.

Step-5) refer 105 and 106


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To configure multiple servlet programs we need to use multiple servlet

tag and multiple servlet-mapping tag having unique logical name and

unique URL patterns.

Step-5 ) deploy the web application in tomcat server. (make sure tomcat

server is in running mode)

Copy: E:\MIME to tomcat webapp folder.

Step-6) Test the web application

http://locahost:3030/MIME/sturl

103-60,88,115,143,160,165,170,175,

22-May-15

The super class method can be overridden in subclass either with same

modifier or with excess modifier.

The protected method of super class can be overridden with either

same protected modifier or extra public modifier.

The protected service(-,-) /2nd service(-,-) of HttpServlet class can be

overridden our servlet prg class either with same protected modifier or

with extra(excess) public modifier.

Always identify service(-,-) method based on its parameter types not

based on its modifiers (public/protectd)

Javax.servlet.Servlet(I)

http://locahost:3030/MIME/sturlhttp://locahost:3030/MIME/sturlhttp://locahost:3030/MIME/sturl


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^

| implement

Javax.servlet.GenericServlet(Ac)

extends

Javax.servlet.http.HttpServlet(Ac)

extends

Extends servlet class

Html, jsp files will be placed outside of WEB-INF folder.

We can use html prog to generate static web pages and jsp prog to

generate dynamic web pages

WEB-INF and its sub folder is called private area of the web application

i.e outsiders clients cannot use content of that folder directly.

Due to this cgf in web.xml file is mandatory ot access them through url

patternHtml, jsp file will reside out side web-inf folder (public area0 so their

cfg in we-inf file is optional (nor required ) because they can be

accessed by client directly.

Web-inf and its content can only be used by underlying

server/container so it is called private area of the web application.

Html to servlet communicateon:

Html prog/files /pages are given to generate static web pages. This

program can also be use to provide user interface (GUI) to end user


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(Visitor) to submit request to other web resource program like servlet

pgra/jsp progs

Since end users are non-technical people they cannot give direct

request to server./jsp program by typing request url in browser window

to overcome this problem we can use html program based hyperlink

form submition to generate request.

Html to serve communication can be done on three way using

a) Hyperlink (cannot carry end user supplied data)

b) Using form submission(can carry end user supplied data)

c)

Using java script (allow any component to submit the request)

Note: For this the request url of servlet prg as “href”.


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Html pgr cfg in web.xml is not required because it is there placed

outside of

Servlet prog cfg is web.xml is mendatory because it is place inside

Page.html.

Click here to ger wish message

(wishurl is wishsrv servlet prog)

wish Message

In window operating system they has provided a feature UAC( user account

control). It will verify whether user is authorized or not.

To disable UAC control

We have to modify enable lue value to

We can change this value from the following location of registry.

To change the port no we use config folder in that we use a file

server.xml.

Instead of an exe file we can use zip file. when we use the zip file we

use startup.bat file to run tomcat.


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Note:- to run the tomcat we need to set java_home in environment variable.

23-May-15

EVERY web resource pagr of web application like servlet prog/jsp

prg/html prg will have 1 request url, we need to use that request url in

order to send request to that we resource prog.

The web resource program like servlet program that is placed in WEB-

INF and its sub folders (private area ) must be configure in

web.xml file to access from clients

The web resource program like html prog that is placed outside WEB-

INF folder can be access directly from client so its configuration in

web.xml file is not required.


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Note: - form data of form page is goes to as request parameter names, values.

The name of form components will become req parameter name and the

values of form components becomes req parameter values.

Input.html

chck u r voting eligiblity

method="get"


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>

Person name:

person age:

To make the form page generated request going to servlet pr place the request url

of servlet prog as action url of servlet prog as action url (action attribute value of

tag)

When form submits the requests the request goes to that web resource

prog whose “request url” is placed as action rul in the form pages.

The form pages can send either “GET” or “POST” mode request to servlet

prog.

The GET mode request can carries limited amount of data(2K-8K) ,

whereas the “POST “ mode request can carry unlimited amount of data.

When form is submitted the form data is goes to server as request

parameter values like pname=raja&page=30. We can read these values

in our servlet prg by using req.getParameter(-) method.

String s1=req.getParamter(“pname”);//gives raja

String s2=req.getParameter(“page”);//gives 40.

In our servlet prog it is recommended to write request processing logic

in doxxx(-,-) methods , not in service(-,-) methods


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The 7 doxxx(-,-)allows us to process requests in 7 modes, they are like

doGet(-,-) , doPost(-,-),doPut(-,-),doDelete(-,-) doTrace(-,-), doHead(-,-

), doOptions(-,-).

The form page can generated either GET or POST request, so use

doGet(-,-), or doPost(-,-) in servlet prg to process the request.

Prototypes of doxxx(-,-) methods.

Protected void doxxx(HttpServletRequest req,HttpServletReponse res)

throws SE, IOE

(7 methods like this)

Web.xml

Configure “com.nt.VoterSrv” prg with “/vturl pattern and “voter”

logical name.

Request url: http://localhost:3030/VoterApp/input.html


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Application that take persion name age geneder as input and check

is it eligible for merrage or not.

24-May-15

Every servlet program is identified with its url pattern. It helps

programmers to hide technology that is used to develop the web

application.

According to servlet specification there are three types of url pattern.

a) Exact match url pattern

b)

Directory match

c) Extension match

For every servlet url pattern configuration is mandatory.


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All servlet / ServletContainer / jsp container are designed based on

common servlet, jsp specification so they recognized only three types of

url pattern.

Exact match —

Must begin with “/” symbol and must not contain “*” symbol

Can have one or more letters/words separated with “/” symbol.

Ex- /test1

Request Urls-

http://localhost:3030/DateApp/test1 (valid)

http://localhost:3030/DateApp/test1.c (invalid)

http://localhost:3030/DateApp/test1.xyz (invalid)

Note: the one we have used so far comes under ”Exact match

url pattern”.

Other exact match url pattern

1)

Eg1- /test1.c2) Eg2- /abc/xyz/test2.c

3) Eg3- /nt/nt1/test.aspx

Note: - the regularly used url pattern of real time is exact

match.

Directory Match Url pattern

Must begin with “/” symbol and must end with “*” symbol.

Can have multiple letter or word separated with “/” symbol.

Eg:- /images/books/*

Request urls:

http://localhost:3030/DateApp/test1http://localhost:3030/DateApp/test1http://localhost:3030/DateApp/test1.chttp://localhost:3030/DateApp/test1.chttp://localhost:3030/DateApp/test1.xyzhttp://localhost:3030/DateApp/test1.xyzhttp://localhost:3030/DateApp/test1.xyzhttp://localhost:3030/DateApp/test1.chttp://localhost:3030/DateApp/test1


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http://localhost:3030/DateApp/images/books/hello.c (valid)

http://localhost:3030/DateApp/images/abc.c (invalid)

http://localhost:3030/DateApp/books/images /hello.c (valid)

http://localhost:3030/DateApp/images/books (valid)

other examples

eg1:- /abc/xyz/*

eg- /x/y/*

eg- /y/*

eg- /nt/it/Tech/*

Extension Match url pattern

Syntax: *.

Eg- eg- *.do

Request urls

http://localhost:3030/DateApp/abc.do (valid)

http://localhost:3030/DateApp/xyz/abc/x.do (valid)

http://localhost:3030/DateApp/abc.x (invalid)

http://localhost:3030/DateApp/abc.do/xyz.c invalid

http://localhost:3030/DateApp/.do (valid)

Other example:-

Eg1:- *.c

Eg1:- *.nit

Eg1:- *.htm

The servlet that takes all requests having different request urls and

delegates the request other web resource pgors is called Front

http://localhost:3030/DateApp/images/books/hello.chttp://localhost:3030/DateApp/images/books/hello.chttp://localhost:3030/DateApp/images/abc.chttp://localhost:3030/DateApp/images/abc.chttp://localhost:3030/DateApp/books/images%20/hello.chttp://localhost:3030/DateApp/books/images%20/hello.chttp://localhost:3030/DateApp/images/bookshttp://localhost:3030/DateApp/images/bookshttp://localhost:3030/DateApp/abc.dohttp://localhost:3030/DateApp/abc.dohttp://localhost:3030/DateApp/xyz/abc/x.dohttp://localhost:3030/DateApp/xyz/abc/x.dohttp://localhost:3030/DateApp/abc.xhttp://localhost:3030/DateApp/abc.xhttp://localhost:3030/DateApp/abc.do/xyz.chttp://localhost:3030/DateApp/abc.do/xyz.chttp://localhost:3030/DateApp/.dohttp://localhost:3030/DateApp/.dohttp://localhost:3030/DateApp/.dohttp://localhost:3030/DateApp/abc.do/xyz.chttp://localhost:3030/DateApp/abc.xhttp://localhost:3030/DateApp/xyz/abc/x.dohttp://localhost:3030/DateApp/abc.dohttp://localhost:3030/DateApp/images/bookshttp://localhost:3030/DateApp/books/images%20/hello.chttp://localhost:3030/DateApp/images/abc.chttp://localhost:3030/DateApp/images/books/hello.c


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controller servlet. While configuration this servlet we need to use

either directory match or extension match url patterns.

/test1/test2.c

(it is exact match url pattern)

/x/y/*.do (invalid url pattern

formation)

If clash comes between exact match and directory match url pattern

the priority will be given to exact match url pattern.

Srv1 rul pattern: /xyz/* (Directory match)

Srv2 url pattern : /xyz/test.c (exact match)

http://localhost:3030/DateApp/xyz/test.c

here (srv2 will execute)

If clash comes between extension match and directory match url

pattern the priority will be given to Directory match url pattern.

Srv1 rul pattern: /xyz/* (Directory match)

Srv2 url pattern : *.c (extension match)http://localhost:3030/DateApp//xyz/test.c

(Srv1 will execute)

If clash comes between extension match and exact match url pattern

the priority will be given to Directory match url pattern.

Srv1 rul pattern: /test.c (exact match)

Srv2 url pattern : *.c (extension match)http://localhost:3030/DateApp//xyz/test.c

(Srv1 will execute)

If clash comes among all the 3 url patterns the priority will be given

to Exact match.

http://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.chttp://localhost:3030/DateApp/xyz/test.c


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Note: in tomcat 8 server if two servlet prog having same url pattern

exception will be raised.

If multiple servlet prog are having directory match pattern and if clash

is coming between them the priority will be given to more nearer

matches.

If multiple servlet porg are having same logical name then last servlet in

the list gets higher priority.

25-May-15 Radio Button:

Gender: Male

: Female

In servlet program gender=req.getParameter(“gen”);

//Gives either “M” or “F”.

To group multiple radio buttons into single unit give same name

them (allow to select 1 radio button at a time)

Radio button the value kept in “value” attribute as req parameter

value.

(M) or (F)


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In web application develop and to make web application as WODA

application and to support WODA behavior of application we shouldprefer working with relative url instead of relative url.

Page.html

< a href=”http://localhost:3030/wishurl”> wish Msg

-absolute url----------------------------------

< a href=”wishurl”> wish Msg

-relative url----------------------------------

Input.html

< a href=http://localhost:3030/vturl> wish Msg

-absolute url----------------------------------

http://localhost:3030/wishurlhttp://localhost:3030/wishurlhttp://localhost:3030/wishurlhttp://localhost:3030/wishurlhttp://localhost:3030/wishurlhttp://localhost:3030/wishurlhttp://localhost:3030/wishurl


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To install s/w extract the zip file.

For help www.glassfish.org

Procedure to crate user defined domain in Glassfish 4.x server

/bin>asadmin create-domain --adminport=4646

--user=testuser GFNtAJ11

4646 is admin port number

testuser – admin user name

GFNtAJ11 — domain name

Enter admin password: testuesr

Renter admin password: testuser

.

.

.

.

Domain GFNtAJ11 created.

Domain GFNtAJ11 admin port is 4646.

Domain GFNtAJ11 admin user is "testuser".

Command create-domain executed successfully.

http://www.glassfish.org/http://www.glassfish.org/http://www.glassfish.org/


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To change “http” port no of the above domain server:

Go to

\domains\GFNTAJ11\config\domain.xml

And modify port attribute value of first tag.

Procedure to deploy web application in “GFNtAJ11” domain

server through console deployment process.

step-1) keep voterApp.war file ready.

step-2) start “GFNtAj11” domain server of GlassFish4.x

\bin>asadmin start-domain GFNtAJ11

For server console we can “server.log” file of “domain floder”

step-3) Open admin console

http://localhost:4646

Username: testuser

Password: testuser

step-4) deploy the web application.

Admincosle application deployee brows ok deployee launch

Glassfish server internally users the tomcat server supplied jsp, servlet

container.

To perform hard deployment of web application in

“GFNtDomain” server GlassFish 4.x copy either directory

either directory (VoterApp) or war file(VoterApp.war) to

\domains\GFNtAJ11\autodeploy folder.

Requested url: http://localhost:7788/VoterApp/input.html

http://localhost:4646/http://localhost:4646/http://localhost:7788/VoterApp/input.htmlhttp://localhost:7788/VoterApp/input.htmlhttp://localhost:7788/VoterApp/input.htmlhttp://localhost:7788/VoterApp/input.htmlhttp://localhost:4646/


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To stop domain server

\bin>asadmin stop-domain GFNtAJ11

Jboss

Type: Application server s/w

Vendor: Apache / RedHat

Upto Apache- 5 it belong ot Apache and after 5 it belongs to RedHat

Version : 7.x (compatable with jdbk 1.6)

Open source up to version-5

and latter it is commercial.

Default port no:-8080(http)

Allows to create domains

To download s/w: download as zip file from www.jboss.org website

(jboss-as-7.1.1.Final.zip)

| Extract it for installation

Supports only console deployment

internally user Tomcat server

To change http port no of jboss7.x

Go to \standalone\configuration\standalone.xml

file a tag.

To create username and password required admin console:

User \bin\add=user.bat file

http://www.jboss.org/http://www.jboss.org/http://www.jboss.org/http://www.jboss.org/


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Choose Management user

Username : testuser

Password: usertest

Reenter password: usertest;

.

.

.

To perform console deployment of the web application

1.

Prepare war file (VoterApp.war)

2. Start server

\bin\standalone.bat(run as administrator)

3. Open admin console

http://localhost:8899/console/App.html

4. Deploy the web application (VoterApp.war)

Deployements Manage Deploymentsadd contentbrows(voterApp.war)nextsaveenable and now test the

application.

http://localhost:8899/VoterApp/input.html

localhsot:8899/voterApp

http://localhost:8899/console/App.htmlhttp://localhost:8899/console/App.htmlhttp://localhost:8899/VoterApp/input.htmlhttp://localhost:8899/VoterApp/input.htmlhttp://localhost:8899/VoterApp/input.htmlhttp://localhost:8899/console/App.html


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It perform code coverage

Findbugs Eclipse plugins:-

Ctrl+shif+j= documentation

Ctrl+shift+f=format

Code coverage

Codeformatter (.xml) file

Alt+shif+j=document

Ctrl+w-close

Strl+shif+w=close

Ctrl+shift+t= see jar file name of a class

C+s+R=rename methods

Ctrl+shift+l- for listing all shorted

Servlet Listeners(Event handling in servlet programming)

Evnent is an action performed on the component or object. To perform

event handling we need event listeners which given event handling

methods.

The components of envent handling

a) Source objectButton

b)

Evnet class ActionEvent

c) Event Listener ActionListener

d) Event Handling methodactionPerformed(-)


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From servlet api2.3 event handling can be done on request,

servletcontext and HttpSession objects.

Events handling on request object allow us to keep track of when

request obj is created and destroyed and also useful to keep track when

request attribute is added /modified/removed. Based on this we can

know request processing time each request.

Even handling on session obj allows us to keep track of when Session

object is created/ destroyed and also useful to keep track of when

session attribute is added /modified /removed. Based on this we can

know the session duration.Event handling ServletContext obj allows keeping track of when

ServletContext obj created/destroyed and also useful to keep track

when ServletContext attribute is added/modified/ removed. Based on

this we can also know the deployment and unemployment of web

application.

Source object Event class Event Listener Event handlingRequest ServletRequestEve

nt

ServletRequestListen

er

requestInitilized(

-)

requestDestroyed

(-)

Session HttpSeeionEvent HttpSessionListener sessionCreated(-)

sessionDestroyed(

-)

ServletConte

xt

ServletConextEven

t

ServletContextListen

er

contextInitlized(-

)

contextDestroyed

(-)


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Procedure to develop and configure ServletListener:

a) Keep SessionApp application ready

b) Develop the following 3 listener classes developed in com.nt

MyRequestListener.java

public class MyRequestListener implements ServletRequestListener

{

long start,end;

//execute when req obj is created

public void requestInitialized(SevletRequestEvent sre)

{

start=System.curentTimeMillis();

}

//execues when req ob is destroyed

public void requestDestroyed(ServletRequestEvent sre)

{

end=System.currentTimeMillis();

HttpServletRequest req=(HttpServletRequest)sre.getServletRequest();

ServletContext se=sre.getServletContext();

sc.log(req.getRequestURI()+"has taken"+(end-start"+"ms to process

request");

}

}

MySessionListener.java

public class MySessionListener implements HttpSessionListener

{

long start,end;

//executed when session obj is created


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public void sessionCreate(HttpSessionEvent hse)

{

start=System.currentTimesMillis();

//write to log filehse.getSession().getServletContext().log("session started at "+new

Date());

}

//when Session obj destroyed/invalidated

public void sessionDestroyed(HttpSessionEvent hse)

{

end=System.currentTimeMillis();

//write to log file

hse.getSession().getServletContext().log("sesssion ended at"+(end-

start));

hse.getSession().getServletContext().log("session duration"+(end-

start));

}

}

c)

Configure the above two listener classes in web.xml file.

com.nt.listeners.MyRequestListener

com.nt.listeners.MySessionLIstener


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d) Run the app and absorb the log file in tomcat_home/logs folder

Servleconter create the object of servletlistener either during server

startup or during the deployment of the webapplication.

servletListener are not given to perform the regular request , response

model it is given to enabling monatring the with out touching the web

resource application of application.

15-jum-15

understanding protocol http:-

The Hypertext Transfer Protocol (HTTP) is an application-level protocol for

distributed, collaborative, hypermedia information systems. This is the foundationfor data communication for the World Wide Web (i.e. internet) since 1990. HTTP is

a generic and stateless protocol which can be used for other purposes as well

using extensions of its request methods, error codes, and headers.

This tutorial is based on RFC-2616 specification, which defines the protocol

referred to as HTTP/1.1. HTTP/1.1 is a revision of the original HTTP (HTTP/1.0). A

major difference between HTTP/1.0 and HTTP/1.1 is that HTTP/1.0 uses a new

connection for each request/response exchange, where as HTTP/1.1 connection

may be used for one or more request/response exchanges.


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http is application protocol that runs over network protocol tcp/ip

defining set of rules to transfer hypertext between browser to

webserver and vice-versa.

Normal text allows sequential reading.

Hypertext allows non-sequential reading because of hypertext links.

The request URL generates http request containing multiple details they

are H2p2.

HHttp request method (GEG/POST/…)

HHttp request headers (user-agent, referrer, accept,…)

P request parameters( User =raja&pwd=rani)

----query string

httpRequest with example content


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what is difference between request headers and req parameters?

Req Header Req Parameters-Names are unique Names are not unique

Carries browser supplied implicit

data.

Carries end user supplied data

(from data)

Names are fixed and unique. Names are user-defined.


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file:///D:/Tomcat%208.0/webapps/SrvConfigApp/ServletConfigApp.java

16-jun-15

Different way of reading request header values:-

Approach-1)

String s1=req.getHeader(“user-agent”);//gives IE

String s2=req.getHeader(“accept-language”);//gives en-US

Appraoch-2)

Enumeration e=req.getHeaderNames();//Gives all req header names

While(e.hasMoreElements())

{

String name=(String)e.nextElement();//Gives name

String value=req.getHeader(name);//gives value.

Pw.println(name+”--”+value);

}

Displays all the request header names and values.

Note:- we need HttpServletRequest obj to read request header values.

Servlet program can use request header values to know about current

browser using which the request is generated so servlet program can

generated the response according to that browser settings.

List of request headers

accept, accept-language, cookie, referrer, accept-encoding, accept-charset,

host, connection, keep-alive, max-age, user-agent and etc.

http://d/Tomcat%208.0/webapps/SrvConfigApp/ServletConfigApp.javahttp://d/Tomcat%208.0/webapps/SrvConfigApp/ServletConfigApp.javahttp://d/Tomcat%208.0/webapps/SrvConfigApp/ServletConfigApp.java


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For related info on request (ServletRequest, HttpServletRequest,

RequestHeader, and etc. refer page no-84 to 87. And also refer page no-

171-181

Http response:-

When servlet prog gives output to browser window, it goes as http

response and that contains multiple details like SCH details.

Sresponse status (100-599)

100-199information

200-299success

300-399Redirection

400-499-incomplete

500-599-server Error

CResponse content (response body)

The messages placed in pw.println(-) method.H response headers.

(ContentType, contentLength,Localtion, referesh and etc…) and

Miscellaneous info.

Response status codes and response status headers help browsers to

display web page in different formats to display error pates.

For various response status code refer page no-179 to 180

Note: the default status code for servlet is 200.


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When browser gives request the web server takes the request and

passes that req to the container .The container creates request ,

response object for every request, Request object contains a lot of

information given by client along with the request.

Response obj contains headers with default values and default status

code but these values can be changes in our servlet program.


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How can we make our web page getting refreshed automatically?

Ans:- use “refresh” Header as shown below

In servlet prog

res.setHeader(“refresh”,”10”);

(or)Res.setIntHeader(“refresh”,10);

This response header makes browser window to autorefresh the

displayed webpages for every “10” seconds .

This concept is useful while displaying live Game Scores, Stock

market share values in web pages.

List of response headers

Content-Lenght, content-Type, location, refresh, lastModified, server,

Connection, Server, date, content-diposition, cache-control, pragma and

etc.


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(cache-control, pragma – are used for enabling cache/buffering in

browser)

severlet response , httpservlet response and response header refer-page-

87 to

17-Jun-15

Cache-control or pragma:(response header)-

Buffer/cache is temporary memory that holds data for temporary period. In client

environment the buffer at client side holds server supplied result and uses them

across the multiple times for same requests to reduce network round trip between

client and server.

Every browser window contains Buffer and it maintains web resource program

supplied results (given by server) and uses those result across the multiple same

requests to reduce network round-trip.

If web resource program is changing its output dynamically for every request then

it is recommended to disable buffer or cache of browser window otherwise

browser window may show old output. (old result collected from buffer/cache).

To disable buffer or cache of browser window we need to place following code in

servlet program,

res.setHeader(“cahch-control”,”no-cache”);

(or)

res.setHeader(“pragma”, “no-cache”);

Because of the above code every request comes to servlet program and output will

not be collected from buffer.

Eg: the servlet program show live game score should be executed by disabling buffer of

browser window.


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Eg:- the servlet program that shows seven wonders of world (fixed content) is

recommended to execute by enabling the buffer of browser.

To set header value/modify header vlues:-

Res.setHeader(“Headername”,”value”); Res.setIntHeader(“Header Name”,numeric value);

Res.SetDateHeader(“Header name”, Date value);

To add header

res.addHeader(“Headername”,”value”);

Res.addIntHeader(“-,-);

Res.addDateHeader-,-);

To set response status code

res.setSatus(numeric status code);

To send Error message

res.sendError(statuscode,”Error message”);

Direct method to set specific header values

res.setContentType()

res.setContentLength(-)

res.setCharacterEncoding()

Note:- To set buffer size

res.setBufferSize(-);

If multiple threads are acting on single object/variable concurrently then the data

of that obj may corrupt.

This indicates that obj/variable is not thread safe by default. To achieve thread

safety use synchronization concept.

Our servlet program is single instance multiple threads component, so the instance

variable of servlet prog is not thread safe where the local variables placed in

service(-,-) methods are thread safe by default.

Multiple threads acts on single copy of instance variable whereas every thread gets

its own copy of service (-,-) method local variable.


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All requests coming to servlet prog will use single connection to interact with

database s/w, so it gives good performance.

Disadvantage:-

Here Connection objects is instance variable in our servlet class, so it is not

thread safe by default.

Appraoche-2)

Create jdbc connection object in service(-,_)/doxx(-,-) method

Use jdbc connection object in service(-,-) /doxxx(-,-) method

Close jdbc connection object in service(-,-) /doxxx(-,-), so it is thread safe by

default.Advantage:-

Here “connection” object is local variable in service(-,-) //doxxx(-,-), so it is

thread safe by default.

Disadvantage:

Every request given to DB s/w will open one connection with DB s/w i.e multiple

requests will open multiple connections with DB s/ws from servlet prog. This

degrades the performance.

Approache-3)

Get jdbc connection obj from jdbc connection pool begin from service(-,-)

/doxxx(-.-) method.

Use jdbc connection object in service(-,-) /doxxx(-,-) methods.

Return jdbc connection obje back to jdbc connection pool being from service(-,-

)/doxxx(-,-) methods

Advantage:-

a. Connection pool gives reusability of jdbc connection obj, so with min connection

objs we can make max clients talking with DB s/w.


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b. Creating connection objects, closing connection obj will be taken care by jdbc

connection pool. So the programmer is free from that process.

c. Given good performance compare to Approach2.

d. Here the reference variable that holds connection obj of jdbc connection pools is

local to variable so we can achieve thread safety.

Jdbc connection pool is factory that contains set of readily available jdbc

connection obj before actually being used.

Approache-4:-

DAO: - The java class that have separates persistence logic from other logics of the

application makes that logic as reusable logic and flexible logics to modify is called DAO

Class.

Create DAO class having persistence logic

Note: - This DAO class can use direct jdbc connection jdbc or connection pool connection

object.

Create DAO class obj in servlet pro‖s service (-,-) /doxxx(-,-) and use the

persistence logic of DAO class.

Conclusion : use approach-1 for small application

Use approach -3, 4 in large scale application.

Date: 18-Jun-15


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Normal java application compilation and execution takes from cmd prompt.

Servlet prg compilation takes place from cmd prompt and execution takes place

from servlet container of the server.

If normal app uses third party api (like oracle thin driver) then that api related jar

file (ojdbc14.jar) should be added to classpath.

If servlet pro uses third party api then third party api related jar file should be

added to classpath and should be added to WEB-INF\lib folder. Here jar file added

to classpath will be used during the compilation servlet prog and jar file added

WEB-INF\lib folder of web application will be used during the execution of servlet

pog.


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Note:-jar files in classpath: ojdbc14.jar, servlet-api.jar

Page-113 application-5

In multiple web application deployed in a server are using same third party api

then instead of placing that third party api jar file in WEB-IN\lib folder of every

application we can place in only one time in server lib folder to use in multiple web

applications.

Server Server library folder

Tomcat \lib folder

NtAj11Domain ofweblogic

\user_project\domain\NtAj1(domainname)

GFNtAj11Domain of

GlassFish4.x

\user_pojects\domains\GFNtAJ11\lib\ext

folder

JBoss7.x \standalone\lib\ext folder..

Working with server library folder to keep the jar file is not recommended, because

when we move web application from one server to another server or from one

machine to another machine. We need to move the jar files separately.

Servlet container tries to recognized the api used in servlet program in multiple

places and in the following order.

a. In the WEB-INF/classes folder of current web application.

b. In the jar files added to WEB-INF\lib folder of the web application.

c. In the jar files added to server library folder.

Date 19-Jun-15

DBApp web application for Eclipse Project.

DBApp(Eclispe Dynamic web project)

|-- java resources


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|--src

|--com.nt

|--DBsrv.java

|--webcontent

|--input.html

|--WEB-INF

|--web.xml

Jar file: Servlet-api.jar ,ojdbc14/6.jar

The jar files added to build path are not visible in WEB-INF\lib folder directly.

For that we need to perform deployment Assembly operation.

Right click on project --buildPath --cfg built path --deployment

assembly --built path entries --select jar file --finish

What is different between ServletContext and ServletConfig?

It is one per our class object so it is called right hand to our servlet class object.

Servlet container creates this object right after our servlet class object creation

and destroys this object right after our servlet class object destruction.

It is an object of underlying ServletContainer supplied class that implements

javax.servlet.SerletConfig(I).

This obj is useful to know about servlet porg (like getting logical name and to

pass additional info to servlet prog).

Useful to read values form web.xml file to servlet program.

Useful to access ServletContext object being from servlet prog.

ServletContext:-

ServletContext object is one per web application.


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It is called global memory of the web application because data placed in

this object is visible and accessible in all web resource programs of web

application.

It is the object of underlying ServletContainer supplied java class that

implements javax.servlet.ServletContext interface.

ServletContainer creates this object either during deployment of the

web application or during server startup.

ServletContainer destroyed this object when web application is stopped or

reloaded or undeployed.

Using this object

a. We can get server info.

b. We can get servlet API version.

c. We can get path of resource.

d. We can get input stream pointing to a resource.

e. We can get MIME type of resource.

f.

We can get Global init params/context params from web.xml.

g. We can write messages to current day‖s log file.


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In a server total 10 web application are deployed in that 7 web application are there

in running mode and 3 are in stopped can u tel me how many servlet context object

are currently available in the server.

Ans: - (10-3)=7

In a web application there are 10 servlet program in that 5 servlet programs are

already request and another two servlet program are enable with load on startup

can you tell me how many ServletConfig objects are currently available in we

application.

7 servletConfig object are crated.

ServletConfig obj, ServletContext obj, our servlet class obj, request object and

response object are the ServletContainer crated object. That means we cannot crate

those object but we can access those object in our servlet program.

“this” operator/keyword to access our servlet class object.

Override service(-,-)/doxxx(-,-)to accesss req, res objs

Different way accessing ServletConfig obj


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Approach-1) (not recommended to use)

public class TestSrv extends HttpServlet

{

ServletConfig cg;

public void init(ServletConfig cg)

{

this.cg=cg;

//use cg

}

public void service(-,-) //doxxx(-,-) throws SE,IOE

{

//use cg

}

Approach-2)

public class TestSrv extends HttpServlet

{

public void init()

{

ServletConfig cg=getServletConfig();

//use cg

}

public void service(-,-) //doxxx(-,-) throws SE,IOE

{

ServletConfig cg=getServletConfig();

//use cg

}

}

Different ways of accessing ServletContext object:-

Appraoch-1) Not recommended

//access ServletConfig obj

ServletConfig cg=getServletConfig ();

//getServletConfig() it is public method of GenericServlet can be access


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directly without class name.

//Access ServletContext obj

ServletContext se=cg.getServletContext();

Note:- To access ServletContext obj we need ServletConfig obj directly or indirectly.

Approach-2) Recommended

In Servlet prog

ServletContext se=getServletContext();

// getServletContext it is a public method of GenericServlet which

internally use servletConfig object to access ServletContext object.

Approach-3)From Servlet 3.0 (recommended)

In servlet Prog

ServletContext sc=req.getServletContext();

Date: 20-Jun-15

ServletFilter:-

ServletFilter is special web resource program that can we use as an

intercepting filter having ability to trap request and to trap response.

ServletFilter contain pre-request processing logic and post-response

generation logic.

ServletFilter can be mapped with other web resource prog of web

application to add additional functionality in web applicationwithout modifying the source code of exiting web source prog…


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With respect to above diagram:-

(2) ServletFilter traps the request and executes pre-request processing

logic.

(4) Servlet executes the request processing logic.

(6) ServletFilter executes post-response generation logic.

ServletFilter can be mapped/ applied on one or more web resource prog

of the web application.

We can take multiple ServletFilter as a chain to apply on 1 or more web

resource prog on a web application.

Basic of ServletFilter :-

ServletFilter is java class that implements javax.servlet.Filter(I) and

provides definition for 3 methods.

a) inti(FilterConfig ) for instantiation

b) doFilter(ServletReqeust req, ServletResponse res,FilterChaning fc)


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FilterChainfor Trapping request, response.

c) destroy() for destruction event.

The above 3 methods are life cycle methods of ServletFilter.

FilterConfig obj is right hand obj to our Filter class obj. we can use

this obj to access ServletContext obj and to access filter init-params

from web.xml file.

There is no FilterContext obj in web application.

ServletContainer creates our Filter class obj either during server is

startup or during the deployment of web application.

ServletContainer destroyed our Filter class obj when the web

application stopped/reloaded/undeployed.

Every Server filter prog must be configured in web.xml file using

, tags.

To map 1 filter with 1 servlet prog the url pattern of servlet prog

must be taken as the url pattern of filter prog.

To map filter with all the web resource prog of web application use

―/*‖ as the url pattern.

ServletContainer create the following objs either during server

startup or during the deployment of the web application.

a. ServletContext obj

b. ServeltListener objs

c.

ServletFilter obj

d. Servlet obj on which is enable.

Sample Filter prog:-

public class MyFilter implements Filter


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{

public void init(FilterConfig fg){

//initializaion logic

}

public void doFilter(ServletRequest req,ServeltResponse res,FilterChain fc)throwsIOE,SE

{

...

...//pre-request processing logic

....

chain.doFilter(req,res);//sends the request to the next filter in chainor destination servlet/jsp program

...

....//post response generation logc

...

}

public void destroy()

{

....//Uninitialazation logic...

}

}

3 types of ServletFilter:-

a.

Request filter(contains only pre-request processing logic)

Eg:- AuthenticationFilter, AuthorizationFilter, RequestDumperFilter and

etc……

b. Respone filter (contains only post-response generation logics)

Eg.- compressionFilter, contentTranslationFilter, SignatureFilter and etc…


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c. Request-Response filter (contains both pre-request processing & post-

response generation logics)

Eg. PerformanceTestFilter…

Mapping servlet filter with servlet/jsp program:-

1. Mapping 1 filter with 1 servlet program

Srv1(servlet) url pattern : /s1url

Frv1(Filter) url pattern: /s1url

2. Mapping 1 filter with 2 servlet program

Srv1(servlet) url pattern : /s1url

Frv1(filter) url pattern: /s1url

Frv2(filter) url pattern: /s1url

3. Mapping 1 filter with all web-resource prog:-

Frv1 url pattern:/*

4. Mapping 2 Filter with all the web-resource program:

Frv1, Frv2 url pattern : /*

5. Mapping certain multiple Filters with certain Servlet program

Srv1 URL pattern: /x/s1url

Srv1 URL pattern: /x/s2url

Srv3 URL pattern: /y/s3url

Srv4 URL pattern: /y/s4url

Frv1 URL pattern: /x/* (will be mapped with srv1, srv2)

Frv1 URL pattern: /y/* (will be mapped with srv3 and srv4)

Example on request Filter:-

(Perform servlet side from valid action using filter)


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Note:- In the above diagram ServletFilter is having inputs validation logic tovalidate the input given to the servlet prog.

FilterChain obj is the objects of the class that implements FilterChain

Interface.

This objects holds information about next filter to execute in chain or

the target servlet or jsp prog to execute.

21-jun-15FilterApp1

|--WEB-INF

|--classes

|--web.xml |--MyFilter.java

|--MyServlet.java

|--com.nt

|--*.class(2)

For above code based example application refer page- 161 and 162 (application)


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When filter is mapped with servlet the filter and servlet program uses

same request and response object.

Tomcat server generates 1 log file per day in \log

folder.

To write log message this log file we need to use following code.

ServletContext se=getServletContext();

Sc.log(“Hellow how are u”);

When multiple Filters are cfg on 1 servlet then they trap request of

servlet prog in the order they of their configuration and response on

the reverse order by their configuration.

Applying authentication filter and Performance Test filter on Servlet

prog:-


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2?---> AuthFilter checks weather user and passwords are correct or not

3E--> if not correct launches one.html asking usr, password again

4---> Tracks req trapping time8---> Tracks the response trapping time to know the time taken for request

processing( Performance test)

Page-162 to 165

23-Jun-15

Jdbc driver class, URL, username, password and etc… are called jdbc

properties.

For better servlet development do not hard code input value inside the

servlet prog gather such value outside the servlet program.

There are two ways to gather input values for servlet prog from outside

the servlet prog

1. Request parameters (Form data)


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770 to 776 — reading and using servlet init parameter values

getServletName java.lang.String getServletName()

Returns the name of this servlet instance. The name may be provided via server

administration, assigned in the web application deployment descriptor, or for anunregistered (and thus unnamed) servlet instance it will be the servlet's class name.

When servlet container create our servlet class object.it uses logical

name given in web.xml as the object identity (reference variable name)

to get this logical name being from servlet prog use.

o cg.getServletName();

Servlet container internally maintain our servlet class object and their

logical name as the key value pairs of HashMap obj elements.

In tomca

natraj servlet2015

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