Chapter2 Servlet Programming

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@2008 Huynh Ngoc Tin

Chapter #2

JAVA SERVLET

PRGRAMMING


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Objective

Basic concepts

9 Why?

9 What is java servlet?

9

Servlet container9 Servlet life circle

9 Servlet API, servlet interface

9

Build, deploy, run a java servlet


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References

[1] Chapt er 3. Prent ice Hall Pt r Java(Tm) Ee 5 Tut or ial,

The (3Rd Edition) (The Java Series)

[2] Marty Hall. Core Servlet and Java Server Page. Sun

Micro System. Prentice Hall PTR; 1 edition 2000.

[3] http://java.sun.com/products/servlet


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Basic concepts

Why?

What is java servlet?

What is servlet container?

Servets on J2EE/JEE Platform Servlet Interface

Servlet Life Circle

Servlet context

Request/Response


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The need for dynamic content.

Applets, one of the earliest attempts toward this goal (the

client side)

At the same time, (CGI) scripts were the main technology

used to generate dynamic content

Limitation: Lack of scalability, Java Servlet technology

was created as a portable way to provide dynamic, user-

oriented content.


Why?


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What is servlet container (Web container)?

A Web container is essentially the component of a Web server

that interacts with the servlet.

The Web container is responsible for managing the life cycle of

servlets

Mapping a URL to a particular servlet and ensuring that the URL

requester has the correct access rights.


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What is servlet container (Web container)?


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Java Servlet on JEE Platform


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Thejavax.servlet andjavax.servlet.http packages provide

interfaces and classes for writing servlets. The Java Servlet API allows a software developer to add

dynamic content to a Web server using the Java platform. The

generated content is commonly HTML, but may be other data

such as XML.

The HttpServlet class provides methods, such as doGet and

doPost, for handling HTTP-specific services.


Servlet API


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Servlet API historyPackages: javax.servlet & javax.servlet.http


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Servlet Interface


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Servlet Interface

Contains methods which are implemented by your servlets

Define methods to:

Init a java servlet.

Handle requests from the client side.

Remove servlet from the server.

Your Servlets can implements Servlet Interface or extends from

a other class that implemented Servlet Interface such as

GenericServlet &HttpServlet.


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Servlet Interface

public abstract class GenericServlet

extends Object implements Servlet,ServletConfig, Serializable

public abstract class HttpServlet

extends GenericServlet implements Serializable

GenericServlet nh ngha 1 servlet c lp

protocol, nh ngha 1 servlet dng trn

Web ta c th cho k tha lp HttpServlet.
http://java.sun.com/j2se/1.5/docs/api/java/lang/Object.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/Servlet.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/ServletConfig.htmlhttp://java.sun.com/j2se/1.5/docs/api/java/io/Serializable.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/GenericServlet.htmlhttp://java.sun.com/j2se/1.5/docs/api/java/io/Serializable.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/GenericServlet.htmlhttp://java.sun.com/j2se/1.5/docs/api/java/io/Serializable.htmlhttp://java.sun.com/j2se/1.5/docs/api/java/io/Serializable.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/ServletConfig.htmlhttp://c/Sun/SDK/docs/api/javax/servlet/Servlet.htmlhttp://java.sun.com/j2se/1.5/docs/api/java/lang/Object.html


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Servlet Interface

Handle request

9

servicemethod: servlet Interface define servicemethod to handle requests from the client side.

9 Servlet Container will call service method tohandle the request from the client side.


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Servlet Interface

HttpRequest methods

HttpServlet have some more methods to handle

HttpRequest:9 doGet for handling HTTP GET requests

9 doPost for handling HTTP POST requests

9

The above methods can are called automatically by service

method


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Servlet life circle

Servlet container have only one instance for each servlet.

Instance is handle by in it , service, dest royin ServletInterface (JEE API).

Servlet Container load and init servlets.

Servlet Container have init servlets before the request come

from the client.

Servlet Container have to choose a servlet for the request and

make decision what servlet will be removed from the server.


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Request & Response


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Request & Response

Request

9 Package all information that comes from the client.

9 Request from Client -> Server follows the HTTP protocol

9 HttpServletRequest methods can summarize, read therequests information.


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Request & Response

Response

9 Package all information that will response for the client.

9 Information in response object are sent to client by HTTTprotocol

9 HttpServletReponse methods can summarize, packageinformation into response object.


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Request & Response

Hypertext Transfer Protocol reference to:

http://djce.org.uk/dumprequest

http://www.w3.org/Protocols/rfc2616/rfc2616.html

http://www.faqs.org/rfcs/rfc2616.html


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Example Login Servlet

Step by step

Define a class name LoginServlet extends from GenericServlet

or HttpServlet class Implement/override the following methods

9 in i t ()

9

service()9 destroy()

Compile and deploy on webserver.

Call to run by URL from the client side


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import javax.servlet.http.*;

import java.io.*;

import java.sql.*;

public class LoginServlet extends HttpServlet {

public void service(HttpServletRequest request,

HttpServletResponse response) throws IOException {

// .

}}


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// inside theservice method

response.setContentType("text/html");

PrintWriter out = response.getWriter();

out.println("");String strUsername = request.getParameter("Username");

String strPassword = request.getParameter("Password");


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Deploy the servlet on Apache Tomcat Web Server

Web Server Apache Tomcat (read the document of other webservers to know how to deploy a servlet)

Step 1: Copy servlet file class into WEB-INF\classes ofyour web application.

Step 2:

Add information about your servlet into web.xml file tonotify with the web server or application server.

WEB-INF\web.xml


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w eb.xm l fi le (configurat ion)

< w eb-app>

LoginServlet

LoginServlet

LoginServlet

/servlets/LoginServlet

< / w eb-app>


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Call a servlet f rom client side

Call a servlet when user clicks submit or login button from theLoginForm/client side

< Form act ion= " ../ ../ serv let s/ LoginServ let "method= "post ">


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Directly

Using the connection pool

Using MySQL JDBC Driver: download andadd mysql-connector-java-5.1.7-bin.jar to

C:\Sun\AppServer\domains\domain1\lib

Connecting to Database


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Connecting to Database


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Connecting to Database- ConnectionPool


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Connecting to Database- Connection Pool


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Connecting to Database-Connection Pool


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Deploy a web app on Tomcat webserver

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Chapter2 Servlet Programming

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