Download servlet engine. UNIT IV UNIT IV MULTI

UNIT IV
UNIT IV
MULTI-TIER APPLICATION DEVELOPMENT
Server side programming – servlets – Java Server Pages - Applet to Applet communication –
applet to Servlet communication - JDBC – Applications on databases – Multimedia streaming
applications – Java Media Framework.
1. Explain about servlets and the life cycle of servlets with an example program. (8)
Servlets:



Servlets are small Java programs that run inside servers.
Servlets extends the server’s functionality and Applets extend the functionality of a web browser. 




Java Servlet technology is one of many technologies available for generating responses
dynamically when an HTTP request is received. (or) Java servlets are executed upon
request from a web browser.
.
Request
Servlet
Response
Client
Server
All servlets execute inside aservlet container,also referred to as aservlet server or a
servlet engine.


A servlet container is a single process that runs a JVM (Java Virtual Machine). JVM is used to
handle each servlets.
Servlet is just a Java class that a web server instantiates when the server is started.
A particular method is called on this instance when the web server receives certain HTTP request
from the web client through the web browsers
Servlet Architecture
Explanation of the architecture diagram:
 






A client application (web browser) sends an HTTP request to the web server.
The servlet container receives the request and
directs it to be processed by the
appropriate servlet.
The servlet does its processing, which may include
components, such as other servlets or JSP’s.
interacting with a database or other server- side
The servlet returns its results to the client- normally
in the form of an HTML, XHTML,
or XML document to display in the browser.
UNIT-4
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Life Cycle of Servlet


o Package
javax.servlet.Servlet.
o The three life cycle methods init(), service(), and destroy() are present in this
servlet communication which should be implemented by all servlets.


init()


 The lifecycle of servlet begins here. 
 This method is called only once to initialize the servlet. 

service()



 Defines an entry point for servicing the requests. 
 It is executed for every incoming requests. 
 It is called only after the servlet is initialized. 

destroy()
 The end of servlet life cycle is indicated by this method. 
 All the resources initialized for servicing the request are cleaned
up. 

Servlet Interface
o The servlet packages define two abstract classes that implement servlet interface



Class GenericServlet (from the package javax.servlet)
The generic
Class HttpServlet (from the package javax.servlet.http)
It is an
interfaces and classes that are implemented and extended by all servlets
 are contained in this class. (service method)



extension or this class is inherited from javax.servlet package. An example
would be a simple servlet that responds using html. (and contains doGet()
and doPost() methods)
o The two most common HTTP request types (also known as request methods)
are get and post.


GET Request



A get request retrieves information from a server. Typically,
an HTML document /XML documents. 

POST Request

o
o
A post request sends data to a server. Typically, post requests are
used to pass user input to a data- handling process, store or
update data on a server. 
The key method in every servlet is service, which accepts both a ServletRequest
object and a ServletResponse object. These object provide access to input and output
streams that allow the servlet to read data from and send data to the client.
If a problem occurs during the execution of a servlet, either ServletExceptions
or IOExceptions are thrown to indicate a problem.
Servlet Interface Methods:



Public void init(ServletConfig config) throws ServletException
 Marks the beginning of a servlets life. 
 It is called only once. 

 The argument ServletConfig encapsulates the initial
parameters and startup configuration of servlet. 


Public void service(ServletRequestreq, ServletResponse res) throws
ServletException, IOException
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



Defines an entry point for servicing the requests. 
It is executed for every incoming client requests. 

Public void destroy()
 Marks the end of the servlet’s life. 
 It is executed only once, when the servlet is removed from
the service. 

When a client connects to a server and request it using HTTP, the request can be of several
different types, called methods. The most commonly and frequently used method
are the following,



HTTP GET

H
T
T

The
P HTTP GET method is used to get information like a document, a chart or results from a database query.
P
O
S addition, it can include some of its own  information as part of the request by appending them using query
In
T
string.

HTTP GET





But it is not allowed to send large amount of information and some servers

limitthe length of the URL’s and query string to about 240 characters.
public void doGet(HttpServletRequest request, HttpServletResponse
response)throws ServletException,IOException
HTTP POST

 The HTTPPOST method is used to post information that is to be stored in the

 The post method uses adifferent technique because it may need to send
database.
magabytes of information.
 It passes its entire request as data of unlimited length, directly over the socket
connection.
public void doPost(HttpServletRequest request, HttpServletResponse
response)throws ServletException,IOException
Servlet program:
myfirstpage.html
<html>
<head>
<title>The servlet
example </title> </head>
<body>
<h1>A simple web application</h1>
<form method="POST" action="WelcomeServlet">
<label for="name">Enter your name </label>
<input type="text" id="name" name="name"/><br><br>
<input type="submit" value="Submit Form"/>
<input type="reset" value="Reset
Form"/> </form>
</body></html>
WelcomeServlet.java
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import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class WelcomeServlet extends HttpServlet {
@Override
public void init(ServletConfig config) throws ServletException
{ super.init(config);
}
protected void doPost(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {
/*
* Get the value of form
parameter */
String name = request.getParameter("name");
String welcomeMessage = "Welcome "+name;
/*
* Set the content type(MIME Type) of the
response. */
response.setContentType("text/html");
PrintWriter out =
response.getWriter(); /*
* Write the HTML to the
response */
out.println("<html>");
out.println("<head>");
out.println("<title> A very simple servlet example</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>"+welcomeMessage+"</h1>");
//out.println("<a href="/servletexample/pages/form.html">"+"Click here to go back to input
page "+"</a>");
out.println("</body>");
out.println("</html>");
out.close();
}
public void destroy() {
}
}
Output:
http://localhost:8081/ServeltWithHTML/caller.html
UNIT-4 Page 4
Servlet response:
web.xml
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<session-config>
<session-timeout>
30 </sessiontimeout>
</sessionconfig> <servlet>
<servlet-name>WelcomeServlet</servlet-name>
<servlet-class>WelcomeServlet</servlet-class>
</servlet>
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<servlet-mapping> <servletname>WelcomeServlet</servlet-name> <urlpattern>/WelcomeServlet</url-pattern>
</servlet-mapping>
</web-app>
2. Explain applet to applet and applet to servlet communication with suitable
program. (16)
Applet To Applet Communication
AppletToApplet.html
<HTML>
<HEAD>
<TITLE> Applet-Applet Communicaton </TITLE> </HEAD>
<BODY BGCOLOR="#FFFFFF">
<h1> Applet-Applet Communicaton </h1>
<applet code="Two" width="400" height="300"
name="Two"> </applet>
<br> <hr> <br>
<applet code="One" width="400" height="300"
name="One"> </applet>
</BODY> </HTML>
First Applet:
One.java
import javax.swing.*; import java.awt.*;
public class One extends JApplet
{
JTextArea taOutput;
public void init()
{
getContentPane().setLayout( new FlowLayout());
taOutput = new JTextArea(5,20); getContentPane().add
(taOutput);
}
public void putText(String str)
{
taOutput.append( str + "\n");
}
UNIT-4 Page 6
}
Second Applet:
Two.java
import javax.swing.*; import java.awt.event.*;
import java.applet.AppletContext; import java.awt.*;
public class Two extends JApplet implements
ActionListener
{
JTextField txtInput;
AppletContext ac;
JButton btnSend;
public void init()
{
getContentPane().setLayout( new FlowLayout());
txtInput = new JTextField(25); getContentPane().add
(txtInput); btnSend = new JButton("Send");
getContentPane().add(btnSend);
btnSend.addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
ac = getAppletContext();
One obj = (One) ac.getApplet("One");
if(obj != null)
{
obj.putText(txtInput.getText());
txtInput.setText("");
}
}
}
OUTPUT:
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APPLET TO SERVLET COMMUNICATION
Sender Applet
EchoApplet.java
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.io.*; import
java.net.*;
/**
* Simple demonstration for an Applet <-> Servlet communication.
*/
public class EchoApplet extends Applet {
private TextField inputField = new TextField();
private TextField outputField = new TextField();
private TextArea exceptionArea = new TextArea();
/**
* Setup the
GUI. */
public void init() {
// set new layout
setLayout(new GridBagLayout());
// add title
Label title = new Label("Echo Applet",
Label.CENTER); title.setFont(new Font("SansSerif",
Font.BOLD, 14)); GridBagConstraints c = new
GridBagConstraints(); c.gridwidth =
GridBagConstraints.REMAINDER; c.weightx = 1.0;
c.fill = GridBagConstraints.HORIZONTAL;
UNIT-4 Page 8
c.insets = new Insets(5, 5, 5, 5);
add(title, c);
// add input label, field and send button
c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("Input:", Label.RIGHT), c);
c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 1.0;
add(inputField, c);
Button sendButton = new Button("Send");
c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
add(sendButton, c);
sendButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{ onSendData();
}
});
// add output label and non-editable field
c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("Output:", Label.RIGHT), c);
c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.fill = GridBagConstraints.HORIZONTAL;
c.weightx = 1.0;
add(outputField, c);
outputField.setEditable(false);
// add exception label and non-editable
textarea c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
add(new Label("Exception:", Label.RIGHT),
c); c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;
c.weighty = 1;
c.fill = GridBagConstraints.BOTH;
add(exceptionArea, c);
exceptionArea.setEditable(false);
}
/**
* Get a connection to
the servlet. */
private URLConnection getServletConnection()
throws MalformedURLException, IOException {
// Connection zum Servlet öffnen
URL urlServlet = new URL(getCodeBase(), "echo");
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Page 9
URLConnection con = urlServlet.openConnection();
// konfigurieren
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches(false);
con.setRequestProperty(
"Content-Type", "application/x-javaserialized-object");
// und zurückliefern
return con;
}
/**
* Send the inputField data to the servlet and show the result in the
outputField. */
private void onSendData()
{ try {
// get input data for sending
String input = inputField.getText();
// send data to the servlet
URLConnection con = getServletConnection();
OutputStream outstream = con.getOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(outstream);
oos.writeObject(input);
oos.flush();
oos.close();
// receive result from servlet
InputStream instr = con.getInputStream();
ObjectInputStream inputFromServlet = new ObjectInputStream(instr);
String result = (String) inputFromServlet.readObject();
inputFromServlet.close();
instr.close();
// show result
outputField.setText(result);
} catch (Exception ex) { ex.printStackTrace();
exceptionArea.setText(ex.toString());
}
}
}
EchoServlet.java
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import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;
/**
* Simple demonstration for an Applet <-> Servlet communication.
*/
public class EchoServlet extends HttpServlet {
/**
* Get a String-object from the applet and send it
back. */
public void doPost( HttpServletRequest
request, HttpServletResponse
response)
throws ServletException, IOException
{ try {
response.setContentType("application/x-java-serialized-object");
// read a String-object from applet
// instead of a String-object, you can transmit any object, which
// is known to the servlet and to the applet
InputStream in = request.getInputStream();
ObjectInputStream inputFromApplet = new ObjectInputStream(in);
String echo = (String) inputFromApplet.readObject();
// echo it to the applet
OutputStream outstr = response.getOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(outstr);
oos.writeObject(echo);
oos.flush();
oos.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
web.xml
<web-app>
<!-- General description of your web application - > <display-name>Echo Servlet</display-name>
<description>
Echo Servlet
</description>
<!-- define servlets and mapping -> <servlet>
<servlet-name>echo</servlet-name>
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<servlet -class>EchoServlet</servletclass> </servlet>
<servlet-mapping> <servletname>echo</servlet-name>
<url-pattern>/echo</url-pattern>
</servlet-mapping>
</web-app>
OUTPUT:
3. Explain the JDBC architecture and write a program to integrate an application with
a database. (8)
OR
Explain how the Database connectivity can be achieved in java and write a test
program to show the database connectivity.
Java Database Connectivity(JDBC)
JDBC is a SQL-level API--one that allows you to execute SQL statements and
retrieve the results.
JDBC Drivers
The JDBC API, found in the java.sql package, contains only a few concrete classes
JDBC drivers are available for most database platforms, from a number of vendors and
in a number of different flavours. There are four driver categories:
Type 1- JDBC-ODBC Bridge Driver
Type 2- Native-API Partly-Java Driver
Type 3- Net-Protocol All-Java Driver
Type 4- Native-Protocol All-Java Driver
Getting a Connection
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The first step in using a JDBC driver to get a database connection involves loading the specific
driver class into the application's JVM
An easy way to load the driver class is to use the Class.forName() method
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
DriverManager class to open a connection to a given database
Connection con =
DriverManager.getConnection("jdbc:odbc:somedb", "user", "passwd");
Executing SQL Queries
use a database, need to execute queries
Statement stmt = con.createStatement();
A query that returns data can be executed using the executeQuery() method of Statement
ResultSet rs = stmt.executeQuery("SELECT * FROM CUSTOMERS");
ResultSet object as a representation of the query result returned one row at a
time. next()method of ResultSet to move from row to row.
The ResultSet interface also boasts a multitude of methods designed for retrieving data from the
current row.
Jspwithmysql.jsp
<%@page import="java.sql.*"%>
<%
response.setHeader("Pragma","no-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires",-1);
try
{
String query=request.getParameter("sql");
if(query!=null)
{
new com.mysql.jdbc.Driver();
String url="jdbc:mysql://localhost:3306/test";
Connection con=DriverManager.getConnection(url,"root","root");
UNIT-4 Page 13
Statement stmt=con.createStatement();
if(stmt.execute(query)==false)
{
out.println(stmt.getUpdateCount()+"rows affected");
}
else
{
ResultSet rs=stmt.getResultSet();
ResultSetMetaData md=rs.getMetaData();
out.println("<table border=\"1\"><tr>");
for(int i=1;i<=md.getColumnCount();i++)
{
out.print("<th>"+md.getColumnName(i)+"</th>");
}
out.println("</tr>");
while(rs.next())
{
out.println("<tr>");
for(int i=1;i<=md.getColumnCount();i++)
{
out.print("<td>"+rs.getString(i)+"</td>");
}
out.println("</tr>");
}
out.println("</table>");
rs.close();
}
stmt.close();
con.close();
}
}
catch(Exception e)
{
out.println(e);
}
%>
<form name="sqlForm" methods="post">
SQL statement:<br><input type="text" name="sql" size="50"><br/>
<input type="reset"><input type="submit" value="Execute">
</form>
Connect the database to JSP Program through the following steps:
o
o
o
o
Load the driver
Class.forName(―sun.jdbc.odbc.JdbcOdbcDriver‖)
Establish connection
Connection conn=DriverManager.getConnection(―jdbc:odbc:sample1‖);
Create a statement that runs sql statements
Statement st=conn.createStatement();
Execute the sql statements
ResultSet rs=st.executeQuery("select *from Table1");
OUTPUT:
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UNIT-4
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4. Explain the BLOB AND CLOB with an example program. OR Explain the
multimedia database application using java. (8)
-
Collection Of Binary Data Stored As Single Entity In DBMS
No Encoding Schema Used, Bytes Storage
Usually Large, Size 4 GB
BLOB Data Not Stored In Table,
Table Contains Reference Address
JDBC Offers Interface java.sql.Blob Provide Generic Functionalities To Handle
BLOB Data In DB
Handle BLOB Data As byte Array
Also, Handled By Java.io.InputStream Class
How MySQL handles BLOBs
Description of the code:
1. First create connection to the database from where you want to retrieve image saved as blob.
2. Create a mysql query to retrieve image value from table column.
3. Retrieves the value of the designated column in the current row of this ResultSet object as a
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Blob object by using getBlob() method.
4. Write data on standard output device.
InsertImage.jsp
<%@ page import="java.sql.*"%>
<%@ page import="java.io.*"%>
<%
Connection con=null;
ResultSet rs=null;
PreparedStatement psmt=null;
FileInputStream fis;
String
url="jdbc:mysql://localhost:3306/test"; try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
con=DriverManager.getConnection(url,"root","root"); File
image=new File("E:/mike.jpg");
psmt=con.prepareStatement("insert into image(name,city,image)"+"values(?,?,?)");
psmt.setString(1,"Michael");
psmt.setString(2,"Chennai");
fis=new FileInputStream(image);
psmt.setBinaryStream(3, (InputStream)fis, (int)(image.length()));
int s = psmt.executeUpdate();
if(s>0) {
%>
<b><font color="Blue">
<% out.println("Image Uploaded successfully
!"); %> </font></b>
<%
}
UNIT-4 Page 17
else {
out.println("unsucessfull to upload image.");
}
con.close();
psmt.close();
}catch(Exception ex){
out.println("Error in connection : "+ex);
}
RetrieveImage2.jsp
<%@ page import="java.sql.*" %>
<%@ page import="java.io.*" %>
<%
String url = "jdbc:mysql://localhost:3306/test";
ResultSet rs = null;
PreparedStatement psmnt =
null; Connection con=null;
InputStream sImage;
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
con=DriverManager.getConnection(url,"root","root");
psmnt = con.prepareStatement("SELECT image FROM image WHERE name = ?");
psmnt.setString(1, "Michael");
rs = psmnt.executeQuery();
if(rs.next()) {
byte[] bytearray = new byte[1048576];
int size=0;
sImage = rs.getBinaryStream(1);
response.reset();
response.setContentType("image/jpeg");
while((size=sImage.read(bytearray))!= -1 ){
response.getOutputStream().write(bytearray,0,size);
}
}
}
catch(Exception ex){
UNIT-4 Page 18
out.println("error :"+ex);
}
finally {
rs.close();
psmnt.close();
con.close();
}
%>
OUTPUT:
Mysql Query:
CREATE TABLE `image` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(32) NOT NULL,
`image` longblob NOT NULL,
city varchar(32),
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=27 ;
Overview Of CLOB
- A Clob is a Character Large Object in a Database.
- A large character data file can be stored asCLOB type
- JDBC provides java.sql.Clob interface for handling large character/text object
- Mysql Supports CLOB there are four Data Types
TINYTEXT, TEXT, MEDIUMTEXT and LONGTEXT which can be taken as
CLOB type and have the maximum lengths and storage requirements
- The maximum length of TINYTEXT has 255 character (8 bits)
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-
TEXT has 16,535 character (16 bits)
MEDIUMTEXT has 16,777,216 character (24 bits)
LONGTEXT has 4,294,967,295 character (32 bits)
INSERTING CLOB VALUES WITH SQL INSERT STATEMENT
1. Use SQL INSERT statement and include the character string a SQL String literal in the
statement
2. Compilation and execution of this program
3. Using String Literals To Insert CLOB Values into database
4. Using prepared statement
5. The CLOB object offers some methods
Length() – returns the number of character in CLOB object, returns long
getSubString(long pos, int length)returns a substring of character from CLOB object
getCharacterStream() – resturns a Reader object from a clob object, resd content
free() – releases resource that clob object holds
5.Explain JMF architecture and its applications. (8)
The Java Media Framework (JMF) is a recent API for Java dealing with real-time multimedia
presentation and effects processing. JMF handles time-based media, media which changes with
respect to time
Various Stages:
input stage - data is read from a source and passed in buffers to the processing stage.
The processing stage consists of a number of codecs and effects designed to modify
the data stream to one suitable for output
Once the processing stage has applied its transformations to the stream, it passes
the information to the output stage
For example, a JMF system may read input from a TV capture card from the local
system capturing input from a VCR in the input stage
Component Architecture
Media Handlers
MediaHandlers are registered for each type of file that JMF must be able to handle. To support
new file formats, a new MediaHandler can be created.
Data Sources
A DataSource handler manages source streams from various inputs. These can be for network
protocols, such as http or ftp, or for simple input from disk.
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Codecs/Effects
Codecs and Effects are components that take an input stream, apply a transformation to it and
output it. Codecs may have different input and output formats, while Effects are simple
transformations of a single input format to an output stream of the same format.
Renderers
A renderer is similar to a Codec, but the final output is somewhere other than another stream. A
VideoRenderer outputs the final data to the screen, but another kind of renderer could output to
different hardware, such as a TV out card.
Mux/Demuxes
Multiplexers and Demultiplexers are used to combine multiple streams into a single stream or viceversa, respectively. They are useful for creating and reading a package of audio and video for saving
to disk as a single file, or transmitting over a network.
Using the Player
The Player class is an easy way to embed multimedia in an application. It handles the setup of the
file handler, video and audio decoders, and media renderers automatically
Capturing Real-time Data
Video and audio data can be captured in real-time from input sources and streamed to files on the
local filesystem.
Capturing Audio
To capture audio, the specified sampling frequency, sample size and number of channels must be
specified.
The source object returned from the Processor can then be turned into a Player object by calling
Manager.createPlayer(). To capture it to an audio file instead, a DataSink can take the data instead:
DataSink sink;
MediaLocator dest = new MediaLocator("file://output.wav"); try {
sink = Manager.createDataSink(source, dest);
sink.open();
sink.start();
} catch (Exception e) { }
Capturing Video
Capturing video is identical to capturing audio. Most video sources have an accompanying audio track
that must be encoded
DataSink filewriter = null; try {
filewriter = Manager.createDataSink( source, dest );
filewriter.open();
filewriter.start();
} catch ( Exception e ) { }
p.start();