JDBC Driver Types and Architecture

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Advance Java Note
What is JDBC?
It is Java Database Connectivity technology.
This technology is an API(Application Programming Interface)
for the java programming language that define how
a client may access a database.
It provides methods for querying and updating data in database.
What are JDBC Drivers?
It is a software component enabling a java application to interact with a database.
JDBC Driver Types
JDBC drivers are divided into four types or levels. The different types of jdbc drivers are:
Type 1: JDBC-ODBC Bridge driver (Bridge)
Type 2: Native-API/partly Java driver (Native)
Type 3: AllJava/Net-protocol driver (Middleware)
Type 4: All Java/Native-protocol driver (Pure)
Type 1 JDBC Driver
JDBC-ODBC Bridge driver
The Type 1 driver translates all JDBC calls into ODBC calls and sends them to the ODBC
driver. ODBC is a generic API. The JDBC-ODBC Bridge driver is recommended only for
experimental use or when no other alternative is available.

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Type 1: JDBC-ODBC Bridge
Advantage
The JDBC-ODBC Bridge allows access to almost any database, since the database's ODBC
drivers are already available.
Disadvantages
1. This driver is not written fully in Java, Type 1 drivers are not portable.
2. A performance issue is seen as a JDBC call goes through the bridge to the ODBC driver,
then to the database, and this applies even in the reverse process. They are the slowest of
all driver types.
3. The client system requires the ODBC Installation to use the driver.
4. Not good for the Web.

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Type 2 JDBC Driver
Native-API/partly Java driver
The distinctive characteristic of type 2 jdbc drivers are
that Type 2 drivers convert JDBC calls into database-specific calls
i.e. this driver is specific to a particular database.
Some distinctive characteristic of type 2 jdbc drivers are shown below. Example: Oracle will
have oracle native api.
Type 2: Native api/ Partly Java Driver

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Advantage
The distinctive characteristic of type 2 jdbc drivers are that
they are typically offer better performance
than the JDBC-ODBC Bridge as the layers
of communication (tiers) are less than that of Type 1
and also it uses Native api which is Database specific.
Disadvantage
1. Native API must be installed in the Client System and hence type 2 drivers cannot be
used for the Internet.
3. This driver is not written in Java Language .Type 2 drivers are not portable.
4. If we change the Database we have to change
the native api as it is specific to a database.
5. Usually not thread safe.
Type 3 JDBC Driver
All Java/Net-protocol driver
Type 3 database requests are passed through
the network to the middle-tier server.
The middle-tier then translates the request to the database.
If the middle-tier server can in turn use Type1, Type 2 or Type 4 drivers.

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Type 3: All Java/ Net-Protocol Driver
Advantage
1. This driver is server-based, so there is no need for any vendor database library to be
present on client machines.
2. This driver is fully written in Java and hence it is Portable.
3. It is suitable for the web.
4. There are many opportunities to optimize portability,
performance, and scalability.
5. The net protocol can be designed to make
the client JDBC driver very small and fast to load.
6. This driver is very flexible allows access to multiple databases using one driver.
7. They are the most efficient amongst all driver types.
Disadvantage

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It requires another server application to install and maintain.
Type 4 JDBC Driver
Native-protocol/all-Java driver
The Type 4 uses java networking libraries
to communicate directly with the database server.
Type 4: Native-protocol/all-Java driver
Advantage
1.They are written in java so that it is portable.
2.It is most suitable for the web.
3. Number of translation layers is very less i.e. type 4 JDBC drivers don't have to translate
database requests to ODBC or a native connectivity interface or to pass the request on to another
server, performance is typically quite good.
3.It don’t need to install special software on the client or server. Further, these drivers can be
downloaded dynamically.

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Disadvantage
With type 4 drivers, the user needs a different driver for each database.
JDBC Architecture
The JDBC API supports both two-tier and three-tier processing models for database access.
1. Two-tier
In such an architecture, the Java application communicates directly with the data source (or
database). The database may reside on the same machine or may be on another machine to which
the clinet machine needs to be connected through a network
2. Three-tier

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In such an architecture, the client machine will send the database access statements to the
middleware, which will then send the statements to the database residing on the third tier of the
architecture, which is normally referred to as the back end. The statements will be processed
there and the result be returned back to the client through the middle tier. This approach will
have all the advantages associated with the 3-tier architecture, such as better maintainability,
easier deployment, scalability, etc.
BASIC JDBC STEPS
1.Load the driver
Loading Database driver is very first step towards making JDBC connectivity with the database.
It is necessary to load the JDBC drivers before attempting to connect to the database.
Syntax
Class.forName(drivername)
E.g
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”).

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2.Establishing Connection
After loading driver, now Establishing Connection with the database with user name and
password.
Syntax
con = DriverManager.getConnection(url+db, user, pass);
E.g
con = DriverManager.getConnection("jdbc:odbc:vision")
3.Create a statement object:
There are three basic types of SQL statements used in the JDBC API:
1.Statement:A Statement represents a general SQL statement without parameters. The method
createStatement() creates a Statement object.
Eg
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("select * from student ");
2.Prepared Statement: A PreparedStatement represents a precompiled SQL statement, with
or without parameters. It is used for SQL commands that need to be executed repeatedly.
Eg 1
PreparedStatement ps = con.prepareStatement(“select * from student where rollno=?”);
ps.setString(1,1);
ResultSet rs = stmt.executeQuery();
Eg2

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PreparedStatement ps = con.prepareStatement(“insert into student values(?,?,?)”);
ps.setInt(1,1);
ps.setString(2,’amol’);
ps.setFloat(3,66.55f);
ResultSet rs = ps.executeUpdate();
3.CallableStatement - CallableStatement objects are used to execute SQL stored procedures
Eg
CallableStatement cstmt=conn.prepareCall(“call student”);
4.Execute a query
An SQL statement can either be a query that return result or operation that manipulates the
database
1.ResultSet executeQuery(String sql):
It is used for statements that return an output result(for only select query)
2.int executeUpdate(String sql): Returns an integer representing the number of rows affected
by the SQL statement. (For only INSERT, DELETE, or UPDATE SQL statements).
5.Process a query:ResultSet provides access to a table of data generated by executing a
Statement. The table rows are retrieved in sequence. A ResultSet maintains a cursor pointing to
its current row of data. The next() method is used to successively step through the rows of the
tabular results.
To access these values, there are getXXX() methods where XXX is a type for example,
getString(), getInt(),getFloat etc.
There are two forms of the getXXX methods:
i. Using columnName: getXXX(String columnName)
ii. Using columnNumber: getXXX(int columnNumber)
Example

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rs.getString(“stuname”));
rs.getString(1);
6.Close the connections
After all work is done, it is important to close the connection. But before the connection is
closed , close the ResultSet and the statement objects.
e.g
rs.close();
stmt.close();
conn.close();
Interface Description
CallableStatement The interface used to execute SQL stored
procedures.
Connection A connection (session) with a specific
database.
PreparedStatement An object that represents a precompiled SQL
statement.
ResultSet A table of data representing a database result
set, which is usually generated by executing
a statement that queries the database.
Statement The object used for executing a static SQL
statement and returning the results it
produces.
CallableStatement The interface used to execute SQL stored
procedures.

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ResultSet their Scroll Types
TYPE_FORWARD_ONLY The result set is not scrollable.
TYPE_SCROLL_INSENSITIVE The result set is scrollable but not sensitive to database
changes.
TYPE_SCROLL_SENSITIVE The result set is scrollable and sensitive to database
changes.

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JDBC-ODBC - Creating DSN for MS Access
➢ Run Control Panel > Administrative Tools > Data Sources (ODBC).
➢ Click the System DSN tab. Then click the Add button.
➢ From the ODBC driver list, select Microsoft Access Driver (*.mdb), ODBCJT32.DLL,
and click the Finish button.
➢ Now fill in the DSN header information as below:

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1.Simple Program
import java.sql.*;
public class OdbcAccessConnection
{
public static void main(String [] args)

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{
Connection con = null;
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con = DriverManager.getConnection("jdbc:odbc:vision");
System.out.println("Connection ok.");
con.close();
}
catch (Exception e)
{
System.err.println(“error”+e);
}
}
}
2.Using select Query
import java.sql.*;
public class OdbcAccessQuery
{
{
try {
con = DriverManager.getConnection("jdbc:odbc:visionstud");
Statement sta = con.createStatement();
ResultSet rs=sta.executeQuery("select * from student");

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while(rs.next())
{
System.out.println("rollno"+rs.getInt(1));
System.out.println("name"+rs.getString(2));
System.out.println("Percentage"+rs.getFloat(3));
}
rs.close();
sta.close();
con.close();
}
catch (Exception e) {
System.err.println(“error”+e);
}
}
}
3 Insertion
import java.sql.*;
import java.io.*;
public class InsQuery
{
{
try {
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter Roll no: ");

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int rno=Integer.parseInt(br.readLine());
System.out.println("Enter Name: ");
String name=br.readLine();
System.out.println("Enter percentage: ");
float per=Float.parseFloat(br.readLine());
String str="insert into student values("+rno+",'"+name+"',"+per+")";
int k=sta.executeUpdate(str);
if(k>0)
System.out.println("Insert "+k);
else
System.out.println("Insert "+k);
while(rs.next())
{ System.out.println("rollno"+rs.getInt(1));
}
rs.close();
sta.close();
con.close();
}
System.err.println("Error"+e);
}

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}
}
4.Update
import java.sql.*;
import java.io.*;
public class UpsQuery
{
{
try {
System.out.println("Enter roll no to update: ");
System.out.println("Enter name to update: ");
String name=br.readLine();
System.out.println("Enter percentage: ");
float per=Float.parseFloat(br.readLine());
String str="update student set name='"+name+"'"+","+"per="+per+" "+"where
rollno="+rno;
if(k>0)
System.out.println("Update "+k);
else
System.out.println("Update "+k);
while(rs.next())
{

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}
rs.close();
sta.close();
con.close();
}
System.err.println("Exception: "+e);
}
}
}
5.Delete
import java.sql.*;
import java.io.*;
public class DelQuery
{
{
try {
System.out.println("Enter roll no to delete: ");
String str="Delete from student where rollno="+rno;
if(k>0)
System.out.println("Delete "+k);
else
System.out.println("Delete "+k);
while(rs.next())
{

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}
rs.close();
sta.close();
con.close();
}
catch (Exception e)
{
System.err.println("Exception: "+e);
}
}
}
6.Searching
import java.sql.*;
import java.io.*;
public class SearchQuery
{
{
try {
System.out.println("Enter rno which U want to search.");
String str="select * from student where rollno="+rno;
ResultSet rs=sta.executeQuery(str);

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while(rs.next())
{
System.out.println("tRoll No: "+rs.getInt(1)+"ntName: "+rs.getString(2)+
"ntPercentage: "+ rs.getFloat(3));
}
rs.close();
sta.close();
con.close();
}
System.err.println("error "+e);
}
}
}

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MultiThreading
MuliProcessing
• This allows many processes to run simultaneously.
• Process is a running instance of the program. i.e. an operating system process.
CPU time is shared between different processes.
• OS provides context switching mechanism, which enables to switch between the
processes.
• Program’s entire contents (e.g. variables, global variables, functions) are stored
separately in their own context.
Example:- MS-Word and MS-Excel applications running simultaneously. (or any
two applications for that matter)
MultiThreading
• It allows many tasks within a program (process) to run simultaneously.
• Each such task is called as a Thread.
• Each Thread runs in a separate context.
• Each Thread has a beginning , a body,& an end
• Example:- Lets take a typical application like MS-Word. There are various independent
tasks going on, like displaying GUI, auto-saving the file, typing in text, spell-checking,
printing the file contents etc…

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Thread
• Thread is an independent sequential path of execution within a program. i.e.
separate call stack.
• Many threads run concurrently within a program.
• At runtime, threads in a program exist in a common memory space and can share both
data and code.
Start Start Start
Switching switching
How To Thread Created?
Threads can be achieved in one of the two ways –
1 Extending java.lang.Thread class.
2 Implementing java.lang.Runnable interface
1.Using Extending java.lang.Thread class.
To Define a class that extends Thread class & override its run() with code required by
thread.
Steps as Follows
Main Thread
Threads A Threads B Threads C

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1.Declare the class as extending the Thread class
Class Vision extends Thread
{
-----------
}
Where Vision is name of thread.
2.Implement the run() method.i.e Responsible for executing of code the thread will execute.
public void run()
{
-------
-----
}
3.Create a thread object & call the start() method to initiate the thread execution.
class A extends Thread
{
public void run()
{
for(int i=1;i<=5;i++)
{
System.out.println("n From Thread A:i="+i);
}
System.out.println("n Exit from A");
}
}
class B extends Thread
{
public void run()
{

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for(int j=1;j<=5;j++)
{
System.out.println("n From Thread B:j="+j);
}
System.out.println("n Exit from B");
}
}
class C extends Thread
{
public void run()
{
for(int k=1;k<=5;k++)
{
System.out.println("n From Thread C:k="+k);
}
System.out.println("n Exit from C");
}
}
class ThreadTest
{
public static void main(String args[])
{
A t1=new A();
//new A().start();
t1.start();//invoke run method
B t2=new B();

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C t3=new C();
}
}
2.Implementing java.lang.Runnable interface
Steps as follows
1.Declare the class as implementing the runnable interface.
2.Implement the run() method.
3.Create a thread by defining an object that is instantiated from “runnable” class as the
target of the thread.
4.Call the thread’s start() method to run the thread.
class A implements Runnable
{
public void run()
{
{
System.out.println("tThread A :"+i);
}
System.out.println("End of thread A");
}
}
class RunnableTest
{
{

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A r=new A();
Thread tx=new Thread(r);
tx.start();
System.out.println("End of main thread");
}
}
Life Cycle of thread
1. Newborn state
2. Runnable state
3. Running state
4. Blocked state
5. Dead state
newborn
Running
Runnable
Blocked
Dead
stop
stop
stop
Resume
Notify
Suspend
Sleep
wait
start
yield
Active
Thread
New
Thread
Idle
Thread

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1 Newborn state
It create a thread object, the thread is born & is said to be newborn state.
2. Runnable state
It means thread is ready for execution & is waiting for the availability of processor.
The processor of assigning time to threads is known as timing-slicing.
yield
……
Runnable thread
If a thread to leave control to another thread of equal priority before its turn comes,it can
done by using yield() method
3.Running state
It means that the processor has given its time to the thread for its execution.
The thread runs until it leaves control on its own or it is preempted by higher priority
thread.A running thread my leaves its control in one of the following
1.suspend():
It has been suspended using suspend() method. A suspended thread can be received by
using resume() method.
Resume()
Running Runable Suspended

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2.sleep()
It can put thread to sleep for a specified time period using sleep(t) method.(t is time
milliseconds).
Sleep(t)
After t
Running Runable Sleeping
3.wait()
It has been hold to wait until some event occurs. This is done using wait() method. The
thread can be scheduled to run again using notify() method.
Wait Notify()
Running Runable waiting
4.Blocked state
A thread is said to be blocked when it is prevented from entering into runnable state &
subsequently the running state. This happens when the thread is suspended,sleeping or waiting.
A blocked thread is considered “not runnable” but not dead .
5.Dead state
Every Thread has a life cycle. A running threads ends its life when it has completed executing its
run() method.

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Display the main Thread.
class CurrentThreadDemo
{
{
Thread t = Thread.currentThread();
System.out.println("Current thread: " + t);
// change the name of the thread
t.setName("My Thread");
System.out.println("After name change: " + t.getName());
try
{
for(int n = 6; n > 0; n--)
{
System.out.println(n);
}
}
catch (Exception e)
{
}
}
}
Threads priority
Each thread is assigned a priority, which affects the order it is scheduled for running.
i.e Threads are assigned priorities that the thread scheduler can use to determine how the threads
will be scheduled.

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The following static final integer constants are defined in the Thread class:
• MIN_PRIORITY =0( Lowest Priority)
• NORM_PRIORITY =5 (Default Priority)
• MAX_PRIORITY =10 (Highest Priority)
setPriority():It can modify a thread’s priority at any time after its creation using the
setPriority() method.
Threadname.setPriority(int number)
Where number is priority number.
getPriority(): It retrieve the thread priority value
{ public void run()
{
{
System.out.println("n From Thread A:i="+i);
}
System.out.println("n Exit from A");
}
}
{ public void run()
{
for(int j=1;j<=5;j++)
{ System.out.println("n From Thread B:j="+j);
}
System.out.println("n Exit from B");
}
}

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class C extends Thread
{ public void run()
{
for(int k=1;k<=5;k++)
{ System.out.println("n From Thread C:k="+k);
}
System.out.println("n Exit from C");
}
}
public class ThreadPriority
{ public static void main(String args[])
{
A t1=new A();
B t2=new B();
C t3=new C();
t3.setPriority(Thread.MAX_PRIORITY);
t1.setPriority(Thread.MIN_PRIORITY);
t3.start();
t1.start();
t2.start();
}
}
Threads Method
1. isAlive() method:
Returns true if the thread is alive, otherwise false.
public final boolean isAlive()
2.join() method:

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The join() method waits for a thread to die.(A thread to wait until the completion of
another
thread before continue.
public void join()
{
public void run()
{
System.out.println("A Thread");
}
}
{
public void run()
{
System.out.println("B Thread");
}
}
class ThreadTest
{
{
try
{
A t1=new A();

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B t2=new B();
t1.join();
t2.join();
System.out.println("Main parent thread");
System.out.println("A thread "+t1.isAlive());
System.out.println("B thread "+t2.isAlive());
}
catch(Exception e)
{
System.out.println("error"+e);
}
}
}
What is mean by Synchronization?
When two or more threads need access to a shared resource,
they need to ensure that the resource will be used by only one thread at a time.
This process by which this is achieved is called Synchronization.
This is the general form of the synchronized statement:
synchronized method1 ()
{
// statements to be synchronized
}

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When it declare a method synchronized, Java creates a “Monitor” & hands it over to the
thread that calls the method first time. As long as the thread holds the monitor, no other thread
can enter the synchronized section of code.
When thread has completed its work of using synchronized method(or block of code),it
will hand over the monitor to the next thread that is ready to use same resource.
Using synchronized
class Callme
{
synchronized void call(String msg)
{
System.out.print("[" + msg);
System.out.println("]");
}
}
class Caller implements Runnable
{
String msg;
Callme target;
Thread t;
public Caller(Callme targ, String s)
{
target = targ;
msg = s;
t = new Thread(this);
t.start();
}
public void run()
{

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target.call(msg);
}
}
public class Synch
{
{
Callme target = new Callme();
Caller ob1 = new Caller(target, "Hello");
Caller ob2 = new Caller(target, "Synchronized");
Caller ob3 = new Caller(target, "World");
}
}
Java - Interthread Communication
When multiple threads are running in an application, it become necessary for the threads to
communicate(talk) with each other such communication called as interthread communication.
The thread can communicate by either sharing data or indicating when a specific activity has
completed.
Methods for interthread communication
wait( ): Causes the current thread to wait until another thread invokes the notify().
Notify( ): Wakes up a single thread that is waiting on this object's monitor.
notifyAll( ): Wakes up all the threads that called wait( ) on the same object.
Join():The join() method waits for a thread to die.(A thread to wait until the completion of
another thread before continue.

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NETWORKING
Networking Basics
Protocol
A protocol is a set of rules and standards for communication. A protocol specifies the
format of data being sent over the Internet, along with how and when it is sent. Three
important protocols used in the Internet are:
1. IP (Internet Protocol): is a network layer protocol that breaks data into small packets
and routes them using IP addresses.
2. TCP (Transmission Control Protocol): This protocol is used for connection-oriented
communication between two applications on two different machines. It is most reliable
and implements a connection as a stream of bytes from source to destination.
2. UDP (User Datagram Protocol): It is a connection less protocol
and used typically for
request and reply services. It is less reliable but faster than TCP.
Addressing
1. MAC Address: Each machine is uniquely identified by a physical address, address of
the network interface card. It is 48-bit address represented as 12 hexadecimal characters:
For Example: 00:09:5B:EC:EE:F2
3. IP Address: It is used to uniquely identify a network
and a machine in the network.
It
is referred as global addressing scheme.
Also called as logical address. Currently used
type of IP addresses is: Ipv4 – 32-bit address and Ipv6 – 128-bit address.
For Example:
Ipv4 – 192.168.16.1
Ipv6 – 0001:0BA0:01E0:D001:0000:0000:D0F0:0010

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4. Port Address: It is the address used in the network to
identify the application on the network.
Domain Name Service (DNS)
It is very difficult to remember the IP addresses of machines
in a network. Instead, we
can identify a machine using a “domain name”
which is character based naming
mechanism. Example: www.google.com.
The mapping between the domain name and the
IP address is done by a service called DNS.
URL
A URL (Uniform Resource Locator) is a unique identifier for any resource located on the
Internet. The syntax for URL is given as:
<protocol>://<hostname>[:<port>][/<pathname>][/<filename>[#<section>]]
Sockets
A socket represents the end-point of the network communication. It provides a simple
read/write interface and hides the implementation details network and transport layer
protocols. It is used to indicate one of the two end-points of a communication link
between two processes. When client wishes to make connection to a server, it will create
a socket at its end of the communication link.
The socket concept was developed in the first networked version of UNIX developed at
the University of California at Berkeley. So sockets are also known as Berkeley Sockets.
Ports
A port number identifies a specific application running in the machine.
A port number is a
number in the range 1-65535.
Reserved Ports: TCP/IP protocol reserves port number
in the range 1-1023 for the use of
specified standard services, often referred to as “well-known” services.

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The java.net Package
The java.net package provides classes and interfaces for implementing network
applications such as sockets, network addresses, Uniform Resource Locators (URLs) etc.
some important interfaces, classes and exceptions as follows :
InetAddress Class
Java InetAddress class represents an IP address. The java.net.InetAddress class provides
methods to get the IP of any host name for example www.google.com, www.facebook.com etc.
Method Description
public static InetAddress getByName(String
host) throws UnknownHostException
it returns the instance of InetAddress
containing LocalHost IP and name.
public static InetAddress getLocalHost() throws
UnknownHostException
it returns the instance of InetAdddress
containing local host name and address.
public String getHostName() it returns the host name of the IP
address.
public String getHostAddress() it returns the IP address in string format.
URL Class
As the name suggests, it provides a uniform way to locate resources on the web. Every
browser uses them to identify information on the web. The URL class provides a simple
API to access information across net using URLs.
The class has the following constructors:
1. URL(String url_str): Creates a URL object based on the string parameter. If the
URL cannot be correctly parsed, a MalformedURLException will be thrown.
2. URL(String protocol, String host, String path): Creates a URL object with the
specified protocol, host and path.
3. URL(String protocol, String host, int port, String path): Creates a URL object
with the specified protocol, host, port and file path.
4. URL(URL urlObj, String urlSpecifier): Allows you to use an existing URL as a
reference context and then create a new URL from that context.

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Method Description
public String getProtocol() it returns the protocol of the URL.
public String getHost() it returns the host name of the URL.
public String getPort() it returns the Port Number of the URL.
public String getFile() it returns the file name of the URL.
public URLConnection
openConnection()
it returns the instance of URLConnection i.e.
associated with this URL.
URLConnection Class
The Java URLConnection class represents a communication link between the URL and the
application. This class can be used to read and write data to the specified resource referred by the
URL.
public class URLConnectionExample
{
public static void main(String[] args)
{
try
{
URL url=new URL("http://www.visionacademe.com/java-tutorial");
URLConnection urlcon=url.openConnection();
InputStream stream=urlcon.getInputStream();
int i;
while((i=stream.read())!=-1)
{
System.out.print((char)i);
}
}catch(Exception e)
{
System.out.println(e);
}
}
}
Connection Oriented Communication
Using Socket Java performs the network communication. Sockets enables to transfer data

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through certain port. Socket class of Java makes it easy to write the socket program
Sockets are broken into two types:
1. Datagram sockets (UDP Socket)
1.A Datagram socket uses user datagram protocol (UDP) to send datagrams (self contained units
of information) in a connectionless manner.
2.This method does not guarantee delivery of the datagram.
3.The advantage is the datagram sockets require relatively few resources and so communication
is faster.
4.Typically request-reply types of application use datagram socket.
5.Java uses java.net.DatagramSocket class to create datagram socket. The
java.net.DatagramPacket represents a datagram.
2. Stream Socket (TCP Socket)
1.A stream socket is a “connected” socket through which data is transferred continuously.
2. It use TCP to create a connection between the client and server. TCP/IP sockets are used to
implement reliable, bidirectional, persistent, point to point, stream-based connection between
hosts on the internet.
3. The benefit of using a stream socket is the communication is reliable. because once
connected ,the communication link is available till it is disconnected. So data transmission is
done in real-time and data arrives reliably in the same order that it was sent. however this
requires more resource. Application like file transfer require a reliable communication. For such
application stream sockets are better.
4. Java uses java.net.Socket class to create stream socket for client and java.net.ServerSocket
for server.
Difference between Datagram and Stream socket
1.DatagramSocket is for sending UDP datagram
Stream socket is used for sending TCP packets.

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2. DatagramSocket is a packet based socket.
Stream socket is a byte oriented socket.
3. DatagramSocket are unreliable. They may be dropped ,duplicate and delivered out of order.
Stream socket is reliable ,if datas are lost on the way, TCP automatically re-sends.
4. DatagramSocket have less overheads and so faster.
Stream sockets require more overhead and are slower.
5.Application which use datagram sockets are request-reply type of application such as DNS
lookups,PING and SMTP.
Stream sockets are used for application like file transfer which require reliability.
6.For Datagram Socket used following class
java.net.DatagramSocket class
java.net.DatagramPacket class
For Stream Socket used following class
java.net.Socket class
java.net.ServerSocket class
7Datagram Socket uses connection less mechanism
Stream Socket uses connection oriented mechanism
ServerSocket Class
This class is used to create a server that listens for incoming connections from clients. It
is possible for client to connect with the server when server socket binds itself to a
specific port. The various constructors of the ServerSocket class are:

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1. ServerSocket(int port): binds the server socket to the specified port number. If 0 is
passed, any free port will be used. However, clients will be unable to access the
service unless notified the port number.
2. ServerSocket(int port, int numberOfClients): Binds the server socket to the
specified port number and allocates sufficient space to the queue to support the
specified number of client sockets.
3. ServerSocket(int port, int numberOfClients, InetAddress address): Binds the
server socket to the specified port number and allocates sufficient space to the queue
to support the specified number of client sockets and the IP address to which this
socket binds
The various methods of this class are:
Method Description
Socket Class
This class is used to represents a TCP client socket, which connects to a server socket and
initiate protocol exchanges. The various constructors of this class are:
1. Socket(InetAddress address, int port): creates a socket connected to the specified
IP address and port. Can throw an IOException.

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2. Socket(String host, int port): creates a socket connected to the specified host and
port. Can throw an UnknownHostException or an IOException.
How to create a server socket
1. Create a ServerSocket object which listen to a specific port.
2. Call the accept() method which accepts client request. This method return the client
socket object.
3. Use the socket object to communication with the client
import java.net.*;
import java.io.*;
public class Server
{
public static void main(String[] ar)

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{
try
{
int port = 6666;
ServerSocket ss = new ServerSocket(port);
System.out.println("Waiting for a client...");
Socket socket = ss.accept();
InputStream sin = socket.getInputStream();
DataInputStream in = new DataInputStream(sin);
String line = null;
while(true)
{
line = in.readUTF();
System.out.println(“Receving line from client : " + line);
System.out.println();
}
}
catch(Exception e)
{
}
}
}
How to create a client socket
1.Create an object of the socket class using the server names and port as parameter.
2.Communication with the server.
3.Close the socket
//Client
import java.net.*;

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import java.io.*;
public class Client
{
public static void main(String[] ar)
{
try
{
int serverPort = 6666;
String address = "127.0.0.1";
InetAddress ipAddress = InetAddress.getByName(address);
Socket socket = new Socket(ipAddress, serverPort);
OutputStream sout = socket.getOutputStream();
DataOutputStream out = new DataOutputStream(sout);
BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
String line = null;
while(true)
{
line = keyboard.readLine();
System.out.println("Sending this line to the server...");
out.writeUTF(line); // send the above line to the server.
out.flush();
System.out.println();
}
}
catch(Exception e)
{
}
}
}

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Servlet
What Web server?
➢ Apache is a very popular server
➢ 66% of the web sites on the Internet use Apache
Apache is:
• Full-featured and extensible
• Efficient
• Robust
• Secure (at least, more secure than other servers)
• Up to date with current standards
• Open source
• Free
What is Tomcat?
Tomcat is the Servlet Engine that handles servlet requests for Apache.
➢Tomcat is a “helper application” for Apache
➢It’s best to think of Tomcat as a “servlet container”
What is servlet?
A servlet is a web component,managed by a container, that generates dynamic content.
➢ Client sends a request to server
➢ Server starts a servlet
➢ Servlet computes a result for server and does not quit
➢ Server returns response to client

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➢ Another client sends a request
➢ Server calls the servlet again
The Life Cycle of a Servlet
1) Servlet class is loaded
The classloader is responsible to load the servlet class. The servlet class is loaded when the first
request for the servlet is received by the web container.
2) Servlet instance is created
The web container creates the instance of a servlet after loading the servlet class. The servlet
instance is created only once in the servlet life cycle.
3) init method is invoked
The web container calls the init method only once after creating the servlet instance.
The init method is used to initialize the servlet. It is the life cycle method of the
javax.servlet.Servlet interface. Syntax of the init method is given below:
public void init(ServletConfig config) throws ServletException
4) service method is invoked
The service() method of the Servlet is invoked to inform the Servlet about the client requests.
This method uses ServletRequest object to collect the data requested by the client.

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This method uses ServletResponse object to generate the output content.
public void service(ServletRequest request, ServletResponse response)
throws ServletException, IOException
5) destroy method is invoked
When a servlet is unloaded by the servlet container, its destroy() method is called. This step is
only executed once, since a servlet is only unloaded once.
public void destroy()
The Servlet API
It includeTwo packages:
▪ javax.servlet
▪ javax.servlet.http
1.The javax.servlet Package

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The javax.servlet package contains a number of interfaces and classes that establish
the framework in which servlets operate.
Servlet Declares life cycle methods for a servlet.
ServletConfig Allows servlets to get initialization parameters.
ServletContext Enables servlets to log events and access
Information about their environment.
ServletRequest Used to read data from a client request.
ServletResponse Used to write data to a client response.
SingleThreadModel Indicates that the servlet is thread safe.
Class Description
GenericServlet Implements the Servlet and ServletConfig
interfaces.
ServletInputStream Provides an input stream for reading requests from a
client.
ServletOutputStream Provides an output stream for writing responses to a
client.
2.javax.servlet.http Package
HttpServletRequest Enables servlets to read data from an HTTP request.
HttpServletResponse Enables servlets to write data to an HTTP response.
HttpSession Allows session data to be read and written.
HttpSessionBindingListener Informs an object that it is bound to or unbound
from a session.

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Class Description
Cookie Allows state information to be stored on a client machine.
HttpServlet Provides methods to handle HTTP requests and responses.
1.doGet
public void doGet(HttpServletRequest request, HttpServletResponse response)
Where
Input is from the HttpServletRequest parameter
Output is via the HttpServletResponse object, which we have named response
2.doPost
public void doPost(HttpServletRequest request, HttpServletResponse response)

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import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloServlet extends HttpServlet
{
{
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
pw.println("<B> Hi Vision Academy!");
pw.close();
}
}
How to Run
Setting:
1.To install Apache tomcat software
2.Go to the browser(Internet explorer)
3.Start tomcat service.
& type the following URL in the Internet explorer(For Testing)
http://localhost:8080[The server listen to port 8080]

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1. To go to the following path
C:Program FilesApache Software FoundationTomcat 6.0lib
5 To copy the servlet-api & jsp-api file & paste to the following path
C:Program FilesJavajdk1.6.0jrelibext
1.To save above file(HelloServlet.java) following path
C:Program FilesApache Software FoundationTomcat 6.0webappsexamplesWEB-
INFclasses
2 Compile the servlet source code
javac HelloServlet.java
3 To go to the following path
C:Program FilesApache Software FoundationTomcat 6.0webappsexamplesWEB-INF

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4 Open the following file(web.xml)& enter the following entry in the file & save it.
<servlet>
<servlet-name>HelloServlet</servlet-name>
<servlet-class>HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet</servlet-name>
<url-pattern>/servlets/servlet/HelloServlet</url-pattern>
</servlet-mapping>
5.To open internet explorer & type following URL
http://localhost:8080/examples/servlets/servlet/HelloServlet
How To retrieve value from the component
Using doGet method
<html>
<body>

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<center>
<form name="Form1"
method="get"
action="http://localhost:8080/examples/servlets/servlet/GetServlet">
Enter name
<input type=text name=”t”>
<br>
<input type=submit value="Submit">
</body>
</html>
import java.io.*;
import java.util.*;
public class GetServlet extends HttpServlet
{
{
String s = request.getParameter("t");
pw.println(s);
pw.close();
}
}
Using doPost method
<html>
<body>
<center>
<form name="Form1"
method="post"
action="http://localhost:8080/examples/servlets/servlet/PostServlet">
Enter name

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<input type=text name=”t”>
<br>
</body>
</html>
import java.io.*;
import java.util.*;
public class PostServlet extends HttpServlet
{
public void doPost(HttpServletRequest request, HttpServletResponse response)
{
String s = request.getParameter("t");
pw.println(s);
pw.close();
}
}
2
<html>
<body>
<center>
<form name="Form1"
action="http://localhost:8080/examples/servlets/servlet/ColorGetServlet">
<B>Color:</B>
<select name="color" size="1">
<option value="Red">Red</option>
<option value="Green">Green</option>
<option value="Blue">Blue</option>
</select>

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<br><br>
</form>
</body>
</html>
import java.io.*;
public class ColorGetServlet extends HttpServlet
{
{
String color = request.getParameter("color");
pw.println("<B>The selected color is: ");
pw.println(color);
pw.close();
}
}
What is a Cookie?
A "cookie" is a small piece of information sent by a web server to store on a web browser so it
can later be read back from that browser. A cookie’s value identify user
Constructor of Cokkie class
Constructor Description
Cookie() constructs a cookie.
Cookie(String name, String value) constructs a cookie with a specified name and value.
Method of Cookie class
Method Description
public void setMaxAge(int Sets the maximum age of the cookie in seconds.

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expiry)
public String getName()
Returns the name of the cookie. The name cannot be changed
after creation.
public String getValue() Returns the value of the cookie.
public void setName(String
name)
changes the name of the cookie.
public void setValue(String
value)
changes the value of the cookie.
Interface Method Description
Public void addCookie(Cookie ck) method of HttpServletResponse interface is
used to add cookie in response object.
Public Cookie[] getCookies() method of HttpServletRequest interface is used
to return all the cookies from the browser.
Add cookie’s value
<html>
<body>
<center>
<form name="Form1"
method="post"
action="http://localhost:8080/examples/servlets/servlets/AddCookieServlet">
<B>Enter a value for MyCookie:</B>
<input type=textbox name="data" size=25 value="">
</form>
</body>
</html>
import java.io.*;
SOFTWARE DEVELOPMENT

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USING JAVA
public class AddCookieServlet extends HttpServlet
{
public void doPost(HttpServletRequest request,HttpServletResponse response)
{
// Get parameter from HTTP request.
String data = request.getParameter("data");
// Create cookie.
Cookie cookie = new Cookie("MyCookie", data);
// Add cookie to HTTP response.
//cookie.setMaxAge( 60 * 60 * 24 );//24 hours
response.addCookie(cookie);
// Write output to browser.
pw.println("<B>MyCookie has been set to");
pw.println(data);
pw.close();
}
}
Accessing cookie’s value
import java.io.*;
public class GetCookiesServlet extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)
{
// Get cookies from header of HTTP request.
Cookie[] cookies = request.getCookies();
for(int i = 0; i < cookies.length; i++)
{

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String name = cookies[i].getName();
String value = cookies[i].getValue();
pw.println("name = " + name +"; value = " + value);
}
pw.close();
}
}
Session Tracking
HTTP is a stateless protocol.
i.e Each request is independent of the previous one.
In some applications,
it is necessary to save state information so that
information can be collected from several interactions
between a browser and a server. Sessions provide
such a mechanism.
There are several ways through which it can provide unique identifier in request and response.
1. User Authentication – This is the very common way where we user can provide
authentication from the login page and then we can pass the authentication information
between server and client to maintain the session. This is not very effective method
because it wont work if the same user is logged in from different browsers.
2. HTML Hidden Field – We can create a unique hidden field in the HTML and when user
starts navigating, we can set its value unique to the user and keep track of the session.
This method can’t be used with links because it needs the form to be submitted every
time request is made from client to server with the hidden field. Also it’s not secure
because we can get the hidden field value from the HTML source and use it to hack the
session.
3. URL Rewriting – We can append a session identifier parameter with every request and
response to keep track of the session. This is very tedious because we need to keep track
of this parameter in every response and make sure it’s not clashing with other parameters.
4. Cookies: A "cookie" is a small piece of information sent by a web server to store on a
web browser so it can later be read back from that browser. It can maintain a session with
cookies but if the client disables the cookies, then it won’t work.

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5. Session Management API:The servlet API provide methods and classes specifically
designed to handle session.The HttpSession class provide various session tracking
methods
public void setAttribute( String name, Object value )
public Object getAttribute( String name )
public Object removeAttribute( String name )
USING JAA
import java.io.*;
import java.util.*;
public class DateServlet extends HttpServlet
{
public void doGet(HttpServletRequest request,
HttpServletResponse response)throws ServletException, IOException
{
// Get the HttpSession object.
HttpSession hs = request.getSession(true);
// Get writer.
pw.print("<B>");
// Display date/time of last access.
Date date = (Date)hs.getAttribute("date");
if(date != null) {
pw.print("Last access: " + date + "<br>");
}
// Display current date/time.
date = new Date();
hs.setAttribute("date", date);
pw.println("Current date: " + date);
}
}

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Servlet CGI(Common Gateway
Interface)
1. It is written in Java only.
2.It is portable
3. Servlets execute within the
address space of a Web server.
It is not necessary to create a
separate process to handle each
client request.
4 It was inexpensive in terms
of processor and memory
resources.
1.It is written in Perl,C &
C++
2. It is not portable
3. It is to create a separate
process for each client
request.
4.It was also expensive in
terms of processor and
memory resources.
JDBC USING SERVLET
import java.io.*;
import java.sql.*;

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public class Jdconn extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
Statement stmt = null;
ResultSet rs = null;
res.setContentType("text/html");
PrintWriter out = res.getWriter();
try
{
// Get a Connection to the database
con = DriverManager.getConnection("jdbc:odbc:vision2");
// Create a Statement object
stmt = con.createStatement();
// Execute an SQL query, get a ResultSet
rs = stmt.executeQuery("SELECT sname,address FROM stud");
while(rs.next())
{
out.println( rs.getString("sname") + " " + rs.getString("address"));
}
con.close();
}
catch(Exception e)
{
out.println(“error”+e);
}
}
}

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JSP(Java Server Page)
• JSP is a server side program.
• JSP tags to enable dynamic content creation (Combination of HTML & JSP tag).
• JSP provide excellent server side scripting support for creating database driven web
applications
• JSP enable the developers to directly insert java code into jsp file, this makes the
development process very simple and its maintenance also becomes very easy.
• JSP pages are efficient, it loads into the web servers memory on receiving the request very
first time and the subsequent calls are served within a very short period of time.
There are 3 methods in JSP(Life cycle of JSP)
A JSP page undergoes 3 phases during life cycle.
1.Translation phase:In this phase,JSP pages get translated into servlet code.
2.Compilation phase:In this phase, the servlet code compiled. The compilation is done only if
the page is requested the first time or it is modified.
3.Excution phase:This is final phase where jsp servlet methods are executed.These are
jspInit(),_jspService(),jspDestroy()

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1.jspInt()
• This method is identical to the init() method in Java servlet.
• This method is called first when the JSP is requested and is used to initialize objects &
variables that are used throughout the life of the JSP.
public void jspInit()
{
// Initialization code...
}
2.jspDestroy()
• This method is identical to the destroy() method in Java servlet.
• This method is automatically called when JSP terminates normally.
• This method is used for cleanup where resources used during execution of JSP are released.
public void jspDestroy()

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{
// Your cleanup code goes here.
}
3._jspService()
• This method is automatically called & retrieves a connection to HTTP.
public void _jspService(HttpServletRequest request, HttpServletResponse response) {
// Service handling code...
}
JSP Architecture

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JSP Processing:
The following steps explain how the web server creates the web page using JSP:
• As with a normal page, your browser sends an HTTP request to the web server.
• The web server recognizes that the HTTP request is for a JSP page and forwards it to a
JSP engine. This is done by using the URL or JSP page which ends with .jsp instead of
.html.
• The JSP engine loads the JSP page from disk and converts it into a servlet content.
• The JSP engine compiles the servlet into an executable class and forwards the original
request to a servlet engine.
• A part of the web server called the servlet engine loads the Servlet class and executes it.
During execution, the servlet produces an output in HTML format, which the servlet
engine passes to the web server inside an HTTP response.
• The web server forwards the HTTP response to your browser in terms of static HTML
content.
JSP Tags
1.Comment Tags:
It is denoted by
<%--
--%>

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e.g
<%-- This comment will not be visible in the page source --%>
2.Declaration statement tags: This tag is used for defining the functions and variables to be
used in the JSP.
It is denoted by
<%!
%>
Eg
<%! int age=25;%>
3.Scriptlet tags: It is used for Java control statements & loop.
It is denoted by
<%
Eg. %>
<% for(int i=0;i<=3;i++)
{
---
---
}
%>
4.Expression tags: The expression is evaluated and the result is inserted into the HTML page
It is denoted by
<%= expression %>
Eg.
<%=age%>
5.Directive tags:
The jsp directives are messages that tells the web container how to translate a JSP page into the
corresponding servlet.

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There are three types of directives:
o page directive
o include directive
o taglib directive
1.page directive
The page directive defines attributes that apply to an entire JSP page.
It is denoted by
<%@ directive attribute="" %>
Attribute as follows
1.language: It defines the programming language (underlying language) being used in the page.
Syntax of language:
<%@ page language="value" %>
e.g
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
2.Extends: This attribute is used to extend (inherit) the class like JAVA does
Syntax of extends:
<%@ page extends="value" %>
e.g
<%@ page extends="demotest.DemoClass" %>
3.Import: It is used to import Java package into the JSP program.
Syntax of import:

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<%@ page import="value" %>
e.g
<%@page import=” java.sql.*” %
4.contentType:
• It defines the character encoding scheme i.e. it is used to set the content type and the
character set of the response
• The default type of contentType is "text/html; charset=ISO-8859-1".
Syntax of the contentType:
<%@ page contentType="value" %>
e.g
pageEncoding="ISO-8859-1"%>
5.Session
Specifies whether or not the JSP page participates in HTTP sessionsSyntax of session
Syntax
<%@ page session="true/false"%>
e.g
session="false"%>
6.errorPage:
This attribute is used to set the error page for the JSP page if JSP throws an exception and then it
redirects to the exception page.
Syntax of errorPage:
<%@ page errorPage="value" %>

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e.g
<%@ page language="java" contentType="text/html;" pageEncoding="ISO-8859-1"
errorPage="errorHandler.jsp"%>
7. PageEncoding:
The "pageEncoding" attribute defines the character encoding for JSP page.The default is
specified as "ISO-8859-1" if any other is not specified.
Syntax
<%@ page pageEncoding="vaue" %>
Here value specifies the charset value for JSP
Example:
<%@ page language="java" contentType="text/html;" pageEncoding="ISO-8859-1"
isErrorPage="true"%>
2.include directive:
• include directive is used to include one file to the another file
• This included file can be HTML, JSP, text files, etc.
<%@ include file="/header.jsp" %>
e.g
a.jsp
<%="HELLO bcs"%>
p.jsp
<%@ include file="p.jsp" %>
<%="HELLO mcs"%>
3.taglib directive:

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JSP taglib directive is used to define the tag library with "taglib" as the prefix, which we can use
in JSP. (custom tags allows us to defined our own tags).
Syntax of taglib directive:
<%@ taglib uri="uri" prefix="value"%>
Here "uri" attribute is a unique identifier in tag library descriptor and "prefix" attribute is a tag
name.
e.g
<%@ taglib prefix="vtag" uri="http://java.sun.com/jsp/jstl/core" %>
How To run JSP?
<html>
<head>
<title>
Sachin Sir 9823037693
</title>
</head> JSP CODE
<body>
<%="HELLO Sachin Sir"%>
<body>
</html>
Step1 Save the file Hello.jsp into the following path
C:Program FilesApache Software FoundationTomcat 6.0webappsexamplesjsp
Step2 Open the browser & type it in the address bar
http://localhost:8080/examples/jsp/Hello.jsp

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Variables
It can declare your own variables, as usual
Using Function
<html>
<head>
<title>
Sachin Sir 9823037693 Sum of first n numbers
</title>
</head>
<body>
<%! int sumoffirst(int n)
{
int sum=0;
for(int i=1;i<=n;i++)
sum=sum+i;
return(sum);
}
%>
JSP CODE
<p>Sum of first n number:
</p>
<body>
</html>
<%=sumoffirst(5)%>

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JSP provides several predefined variables(implicit object)
Implicit object:These objects are created automatically by JSP container. It can directly use
these object.JSP Implicit Objects are also called pre-defined variables
No. Object & Description
1
request
This is the HttpServletRequest object associated
with the request.
2
response
This is the HttpServletResponse object associated
with the response to the client.
3
out
This is the PrintWriter object used to send output to
the client.
4
session
This is the HttpSession object associated with the
request.
5
application
This is the ServletContext object associated with the
application context.
6
config
This is the ServletConfig object associated with the
page.
7
pageContext
This encapsulates use of server-specific features like
higher performance JspWriters.

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8
page
This is simply a synonym for this, and is used to call
the methods defined by the translated servlet class.
9
Exception
The Exception object allows the exception data to be
accessed by designated JSP.
1.Display html & jsp page separate
l.html
<html>
<head>
<title>Login</title>
</head>
<body>
<form method="post" action="http://localhost:8080/examples/jsp/login.jsp">
Username:<input type="text" name="t1">
<br>
Password:<input type="password"name="t2">
<br>
<input type="submit" value="Login">
<input type="reset" value="Clear">
</body>
</html>

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Login.jsp
<%
String s1=request.getParameter("t1");
String s2=request.getParameter("t2");
if(s1.equals("sachin")&&s2.equals("sachin"))
out.println("Login Sucessfully");
else
out.println("Login incorrect");
%>

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Database connection using jsp
<%@page import="java.sql.*"%>
<%@page import="java.io.*"%>
<html>
<body>
<%
try
{

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while(rs.next())
{
out.println("rollno"+rs.getInt(1));
out.println("name"+rs.getString(2));
out.println("Percentage"+rs.getFloat(3));
}
rs.close();
sta.close();
con.close();
}
catch(Exception e)
{
}
%>
</body>
</html>

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JSP Benefits
• Easy to combine static templates,including HTML or XML.
• JSP pages compile dynamically into servlets.
• JSP makes it easier to author pages "by hand"
• JSP tags for invoking JavaBeansTM components
Compare servlet &jsp
JSP Servlets
JSP is a webpage scripting language that can generate
dynamic content.
Servlets are Java programs that are already
compiled which also creates dynamic web
content.
JSP run slower compared to Servlet as it takes
compilation time to convert into Java Servlets.
Servlets run faster compared to JSP.
It’s easier to code in JSP than in Java Servlets. Its little much code to write here.
In MVC, jsp act as a view. In MVC, servlet act as a controller.
JSP are generally preferred when there is not much
processing of data required.
servlets are best for use when there is more
processing and manipulation involved.
The advantage of JSP programming over servlets is that
we can build custom tags which can directly call Java
beans.
There is no such custom tag facility in servlets.
We can achieve functionality of JSP at client side by
running JavaScript at client side.
There are no such methods for servlets.

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Remote Method Invocation(RMI)
Definition: Java RMI is a mechanism that allows a Java program running on one computer to
apply a method to an object living on a different computer.
OR
RMI enables the programmer to create distributed Java applications, in which the methods of
remote Java objects can be invoked from other Java virtual machines, possibly on different hosts.
OR
The Java Remote Method Invocation (RMI) system allows an object running in one Java virtual
machine to invoke methods on an object running in another Java virtual machine.
RMI is an implementation of the of the Distributed Object programming
model
RMI Architecture Layers

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It consist of following parts
Client: user interface
Server : data source
Stubs
1.The client side object participating object communication is known as stub or proxy.
2. The stub acts as a gateway for client side objects & outgoing requests to server side objects
that are routed through it.
3. The stub wraps client object functionality & by adding the network logic ensures the reliable
communication channel between client & server.
Stub responsibility
1.Initiating the communication towards the server selection
2.Translating calls from caller object
3.Marshaling of arguments: It refers to the process of converting the data or the objects
inbto a byte-stream.
4.Informing the skeleton that the call should be invoked.
5. Passing arguments to skeleton over network.
6. Unmarshalling (converting the byte-stream back to their original data or object) of the
response from skeleton.
7. informing skeleton that call is complete

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Skeletons:
1.The server side object participating object communication is known as skeleton.
2.A skeleton acts as gateways for server side object & all incoming clients requests are routed
through it.
3. The skeleton wraps server object functionality & by adding the network logic ensures the
reliable communication channel between client & server.
Skeleton responsibility
1.Translating incoming data from stub to correct up-calls to server objects.
2.unmarshalling of arguments from received data.
3.To pass arguments to server objects.
4.marshalling of the returned values from server objects.
5. To pass values back to the client stub over the network.
Remote Reference Layer:
(RRL) Part of Java's Remote Method Invocation protocol. RRL exists in both the
RMI client and server. It is used by the stub or skeleton protocol layer and uses the transport
layer. RRL is reponsible for transport-independent functioning of RMI, such as connection
management or unicast/multicast object invocation
Various invocation protocols can be carried out at this layer. Examples are:
• Unicast point-to-point invocation.
• Invocation to replicated object groups.
• Support for a specific replication strategy.
• Support for a persistent reference to the remote object (enabling activation of the remote
object).
• Reconnection strategies (if remote object becomes inaccessible).
Transport Layer:

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The Transport Layer makes the connection between JVMs. All connections are stream-based
network connections that use TCP/IP.
RMI Registry
The Java RMI registry is a remote object that maps name to remote object
i.e For a client communication with a server, the client has to find the location of remote
object.Each &every object to be accessed remotely has to be register with RMI registry with
unique name.so if there is any request for particular object, the registry will direct the request to
the correct object.
public static java.rmi.Remote
lookup(java.lang.String) throws
java.rmi.NotBoundException,
java.net.MalformedURLException,
java.rmi.RemoteException;
It returns the
reference of
the remote
object.
public static void bind(java.lang.String,
java.rmi.Remote) throws
java.rmi.AlreadyBoundException,
It binds the
remote object
with the given

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java.net.MalformedURLException,
java.rmi.RemoteException;
name.
public static void unbind(java.lang.String)
throws java.rmi.RemoteException,
java.rmi.NotBoundException,
java.net.MalformedURLException;
It destroys the
remote object
which is bound
with the given
name.
public static void rebind(java.lang.String,
java.rmi.Remote) throws
java.rmi.RemoteException,
It binds the
remote object
to the new
name.
public static java.lang.String[]
list(java.lang.String) throws
java.rmi.RemoteException,
It returns an
array of the
names of the
remote objects
bound in the
registry.
Steps for implementing RMI system
1. Write and compile Java code for interfaces
2. Write and compile Java code for implementation classes
3. Generate Stub and Skeleton class files from the implementation classes
4. Write Java code for a remote service host program
5. Develop Java code for RMI client program
6. Install and run RMI system

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Step 1:Interfaces
The first step is to write and compile the Java code for the service interface. The Calculator
interface defines all of the remote features offered by the service:
public interface Calculator extends java.rmi.Remote
{
public long add(long a, long b)
throws Exception;
public long sub(long a, long b)
throws Exception;
public long mul(long a, long b)
throws Exception;
public long div(long a, long b)
throws Exception;
}
Copy this file to your directory and compile it with the Java compiler:
C:>rmi>javac Calculator.java
2.Implementation
Next, you write the implementation for the remote service. This is the CalculatorImpl class:
public class CalculatorImpl extends java.rmi.server.UnicastRemoteObject
implements Calculator
{
public CalculatorImpl() throws Exception
{
super();
}

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public long add(long a, long b) throws Exception
{
return a + b;
}
public long sub(long a, long b) throws Exception
{
return a - b;
}
public long mul(long a, long b) throws Exception
{
return a * b;
}
public long div(long a, long b) throws Exception
{
return a / b;
}
}
Again, copy this code into your directory and compile it.
C:>rmi>javac CalculatorImpl.java
3 Stubs and Skeletons
You next use the RMI compiler, rmic, to generate the stub and skeleton files. The compiler
runs on the remote service implementation class file.
C:>rmi >rmic CalculatorImpl
Try this in your directory. After you run rmic you should find the file
CalculatorImpl_Stub.class. , if you are running the Java 2 SDK,
CalculatorImpl_Skel.class.

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Note: rmic is used for stub generator.
4. Server
Remote RMI services must be hosted in a server process.
import java.rmi.Naming;
public class CalculatorServer
{
public CalculatorServer()
{
try
{
Calculator c = new CalculatorImpl();
Naming.rebind("rmi://localhost:1099/CalculatorService",c);//Binding for specified
name where 1st argument object is the remote object being registered & 2nd argument is the
String that names the remote object.
} catch (Exception e) {
System.out.println("Trouble: " + e);
}
}
public static void main(String args[]) {
new CalculatorServer();
}
}
C:>rmi>javac CalculatorServer.java
5.Client
The source code for the client follows:
import java.rmi.Naming;
import java.rmi.RemoteException;

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import java.net.MalformedURLException;
import java.rmi.NotBoundException;
public class CalculatorClient
{
public static void main(String[] args)
{
try
{
Calculator c = (Calculator) Naming.lookup("rmi://localhost/CalculatorService");
System.out.println( c.sub(4, 3) );
System.out.println( c.add(4, 5) );
System.out.println( c.mul(3, 6) );
System.out.println( c.div(9, 3) );
}
catch (Exception e)
{
System.out.println("error"+e);
}
}
}
C:>rmi>javac CalculatorClient.java
6.Running the RMI System
You are now ready to run the system! You need to start three consoles, one for the server,
one for the client, and one for the RMIRegistry.
• Start with the Registry
C:>rmi>start rmiregistry

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• Start the another console for server hosting
C:>rmi>java CalculatorServer
It will start, load the implementation into memory and wait for a client connection.

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• Start the client program.
C:>rmi>java CalculatorClient

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What is JavaBeans?
In Java Platform, JavaBeans are classes that encapsulate many objects into a single object (the
bean). They are serializable, have a zero-argument constructor, and allow access to properties
using getter and setter methods.
Advantages of Java Beans
1. Exposure to other applications
One of the most important advantages of a JavaBean is, the events properties and the methods of
a bean can be exposed directly to another application.
2. Registration to receive events
A JavaBean can be registered to receive events from other objects. However, It can also generate
events that can be sent to other objects.
3. Ease of configuration
We can easily use auxiliary software to configure the JavaBean. However, It can also save the
configuration setting of a JavaBean to persistent storage.
4. Portable
As JavaBeans are built in Java, It can easily port them to any other platform that contains JRE.
5. Lightweight
JavaBeans are light weighted, I.e., we don't need to fulfill any special requirement to use it. Also,
it is very easy to create them. However, it doesn't need a complex system to register components
with JRE.
The other advantages of JavaBeans include reusability, deployment, and customization that can
be archived using JavaBeans.

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Features of JavaBeans
Support for introspection
❖ so that a builder tool can analyze how a bean works
Support for customization
❖ so that when using an application builder a user can customize the
appearance and behavior of a bean
Support for events
❖ as a simple communication metaphor than can be used to connect
up beans
Support for properties
❖ both for customization and for programmatic use
Support for persistence
❖ A bean can be customized in an application builder and then have
its customized state saved away and reloaded later
Using the Bean Developer Kit (BDK)
JavaBeans are reusable software components written in Java. These components may be built
into an application using an appropriate building environment. The Bean Development Kit
(BDK) from Sun includes a simple example of a building environment which uses beans, called
the beanbox.
It displays four windows on the screen:
• ToolBox which lists all beans the BeanBox has found,

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• The BeanBox which is a canvas where you will drop beans and connect them together,
• The Properties sheet which is used to set the properties of the current bean,
• the MethodTracer simple debugging facility.
JAR(Java Archive File)
JAR (Java Archive) is a package file format typically used to aggregate many Java class files
and associated metadata and resources (text, images, etc.) into one file to distribute application
software or libraries on the Java platform.
OR

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A Java Archive File, commonly referred to as a Jar File is nothing more than a compressed
archive file.
Benefits of using Jar files are:
• Decreased download time, since the archive is compressed it takes less time to download
as compare to downloading each individual file.
• Package Versioning, A Jar file may contain vendor and version information about the
files it contains.
• Portability, all Java Runtime Environments know how to handle Jar files.
Creating JAR File
jar cf jar-filename input-files
The c option indicates that you wish to create a jar and the f option indicates that output should
be sent to a file, jar-filename is the name of the resulting Jar file and input-files are the files you
wish to include.
Mainfest File
The Jar file automatically adds a manifest file to the jar file, the file is always in a directory
named META-INF and file is named MANIFEST.MF.This file contains information about the
jar file.
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