Programação Orientada a Objetos Objetos - IEC

Programação Orientada a
Objetos
Programação em Redes
Paulo André Castro
CES-22
IEC - ITA
6. Networking
Sumário
6.1
6.2
6.3
6.4
Introdução
Criando um Servidor Simples usando Stream Sockets
Criando um Cliente Simples usando Stream Sockets
Uma Aplicação Client/Server com Stream Socket
6.5
Manipulando URLs
6.6
Lendo um arquivo em um Web Server
6.7
Segurança e Rede
6.8 Design Patterns usados nos Packages java.io e java.net
6.8.1
Creational Design Patterns
6.8.2
Structural Design Patterns
Paulo André Castro
CES-22
IEC - ITA
6.1 Introduction
• Networking package is java.net
– Socket-based communications
• Applications view networking as streams of data
• Connection-based protocol
• Uses TCP (Transmission Control Protocol)
– Packet-based communications
• Individual packets transmitted
• Connectionless service
• Uses UDP (User Datagram Protocol)
Paulo André Castro
CES-22
IEC - ITA
6.2 Establishing a Simple
Server Using Stream Sockets
• Five steps to create a simple server in Java
– ServerSocket object
• Registers an available port and a maximum number of clients
– Each client connection handled with Socket object
• Server blocks until client connects
– Sending and receiving data
• OutputStream to send and InputStream to receive data
• Methods getInputStream and getOutputstream
– Use on Socket object
– Process phase
• Server and Client communicate via streams
– Close streams and connections
Paulo André Castro
CES-22
IEC - ITA
6.5 Establishing a Simple Client
Using Stream Sockets
• Four steps to create a simple client in Java
– Create a Socket object for the client
– Obtain Socket’s InputStream and
Outputstream
– Process information communicated
– Close streams and Socket
Paulo André Castro
CES-22
IEC - ITA
6.6 Client/Server Interaction with
Stream Socket Connections
• Client/server chat application
– Uses stream sockets as described in last two
sections
Paulo André Castro
CES-22
IEC - ITA
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// Server.java
// Set up a Server that will receive a connection from a client, send
// a string to the client, and close the connection.
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Server extends JFrame {
private JTextField enterField;
private JTextArea displayArea;
private ObjectOutputStream output;
private ObjectInputStream input;
private ServerSocket server;
private Socket connection;
private int counter = 1;
Listen on a
ServerSocket; the
connection is a
Socket
// set up GUI
public Server()
{
super(
super( "Server" );
Container container = getContentPane();
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// create enterField and register listener
enterField = new JTextField();
enterField.setEditable( false );
enterField.addActionListener(
new ActionListener() {
// send message to client
public void actionPerformed( ActionEvent event )
{
sendData( event.getActionCommand() );
enterField.setText( "" );
}
}
);
container.add( enterField, BorderLayout.NORTH
BorderLayout.NORTH );
// create displayArea
displayArea = new JTextArea();
container.add( new JScrollPane( displayArea ),
BorderLayout.CENTER
BorderLayout.CENTER );
setSize( 300,
300, 150 );
setVisible( true );
} // end Server constructor
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// set up and run server
public void runServer()
{
// set up server to receive connections; process connections
try {
// Step 1: Create a ServerSocket.
server = new ServerSocket( 12345,
12345, 100 );
Create ServerSocket
at port 12345 with
queue of length 100
while ( true ) {
try {
waitForConnection();
getStreams();
processConnection();
}
//
//
//
Step
Step
Step
2:
3:
4:
Wait for a connection.
Get input & output streams.
Process connection.
// process EOFException when client closes connection
catch ( EOFException eofException ) {
System.err.println( "Server terminated connection" );
}
finally {
closeConnection();
++counter;
}
Paulo André Castro
// Step 5: Close connection.
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} // end while
} // end try
// process problems with I/O
catch ( IOException ioException ) {
ioException.printStackTrace();
}
} // end method runServer
// wait for connection to arrive, then display connection info
private void waitForConnection() throws IOException
{
Method accept waits
displayMessage( "Waiting for connection\
connection\n" );
connection = server.accept(); // allow server to accept connection for connection
displayMessage( "Connection " + counter + " received from: " +
connection.getInetAddress().getHostName() );
Output name of
}
// get streams to send and receive data
private void getStreams() throws IOException
{
Paulo André Castro
POO
computer that
connected
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// set up output stream for objects
output = new ObjectOutputStream( connection.getOutputStream() );
output.flush(); // flush output buffer to send header information
// set up input stream for objects
input = new ObjectInputStream( connection.getInputStream() );
displayMessage( "\nGot I/O streams\
streams\n" );
}
Method flush
empties output buffer
and sends header
information
// process connection with client
private void processConnection() throws IOException
{
// send connection successful message to client
String message = "Connection successful";
successful";
sendData( message );
// enable enterField so server user can send messages
setTextFieldEditable( true );
do { // process messages sent from client
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// read message and display it
try {
message = ( String ) input.readObject();
displayMessage( "\n" + message );
}
// catch problems reading from client
catch ( ClassNotFoundException classNotFoundException ) {
displayMessage( "\nUnknown object type received" );
}
Read String from
client and display it
} while ( !message.equals( "CLIENT>>> TERMINATE" ) );
} // end method processConnection
// close streams and socket
private void closeConnection()
{
displayMessage( "\nTerminating connection
connection\
\n" );
setTextFieldEditable( false ); // disable enterField
Method
closeConnection
closes streams and
sockets
try {
output.close();
input.close();
connection.close();
}
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catch(
catch( IOException ioException ) {
ioException.printStackTrace();
}
}
// send message to client
private void sendData( String message )
{
// send object to client
try {
output.writeObject( "SERVER>>> " + message );
output.flush();
displayMessage( "\nSERVER>>> " + message );
}
// process problems sending object
catch ( IOException ioException ) {
displayArea.append( "\nError writing object" );
}
Method flush
empties output buffer
and sends header
information
}
// utility method called from other threads to manipulate
// displayArea in the eventevent-dispatch thread
private void displayMessage( final String messageToDisplay )
{
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// display message from eventevent-dispatch thread of execution
SwingUtilities.invokeLater(
new Runnable() { // inner class to ensure GUI updates properly
public void run() // updates displayArea
{
displayArea.append( messageToDisplay );
displayArea.setCaretPosition(
displayArea.getText().length() );
}
}
// end inner class
); // end call to SwingUtilities.invokeLater
}
// utility method called from other threads to manipulate
// enterField in the eventevent-dispatch thread
private void setTextFieldEditable( final boolean editable )
{
// display message from eventevent-dispatch thread of execution
SwingUtilities.invokeLater(
new Runnable() { // inner class to ensure GUI updates properly
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public void run() // sets enterField's editability
{
enterField.setEditable( editable );
}
}
// end inner class
); // end call to SwingUtilities.invokeLater
}
public static void main( String args[] )
{
Server application = new Server();
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE
JFrame.EXIT_ON_CLOSE );
application.runServer();
}
// end class Server
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// Client.java
// Client that reads and displays information sent from a Server.
import java.io.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Client extends JFrame {
private JTextField enterField;
private JTextArea displayArea;
private ObjectOutputStream output;
private ObjectInputStream input;
private String message = "";
"";
private String chatServer;
private Socket client;
The client is a
Socket
// initialize chatServer and set up GUI
public Client( String host )
{
super(
super( "Client" );
chatServer = host; // set server to which this client connects
Container container = getContentPane();
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// create enterField and register listener
enterField = new JTextField();
enterField.setEditable( false );
enterField.addActionListener(
new ActionListener() {
// send message to server
public void actionPerformed( ActionEvent event )
{
sendData( event.getActionCommand() );
enterField.setText( "" );
}
}
);
container.add( enterField, BorderLayout.NORTH
BorderLayout.NORTH );
// create displayArea
displayArea = new JTextArea();
container.add( new JScrollPane( displayArea ),
BorderLayout.CENTER
BorderLayout.CENTER );
setSize( 300,
300, 150 );
setVisible( true );
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} // end Client constructor
// connect to server and process messages from server
private void runClient()
{
// connect to server, get streams, process connection
try {
connectToServer(); // Step 1: Create a Socket to make connection
getStreams();
// Step 2: Get the input and output streams
processConnection(); // Step 3: Process connection
}
// server closed connection
catch ( EOFException eofException ) {
System.err.println( "Client terminated connection" );
}
// process problems communicating with server
catch ( IOException ioException ) {
ioException.printStackTrace();
}
finally {
closeConnection(); // Step 4: Close connection
}
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} // end method runClient
// connect to server
private void connectToServer() throws IOException
{
displayMessage( "Attempting connection\
connection\n" );
// create Socket to make connection to server
client = new Socket( InetAddress.getByName( chatServer ), 12345 );
// display connection information
displayMessage( "Connected to: " +
client.getInetAddress().getHostName() );
}
Create a client that
will connect with port
12345 on the server
Notify the user that we
have connected
// get streams to send and receive data
private void getStreams() throws IOException
{
// set up output stream for objects
output = new ObjectOutputStream( client.getOutputStream() );
output.flush(); // flush output buffer to send header information
// set up input stream for objects
input = new ObjectInputStream( client.getInputStream() );
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POO
Get the streams to
send and receive data
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displayMessage( "\nGot I/O streams\
streams\n" );
}
// process connection with server
private void processConnection() throws IOException
{
// enable enterField so client user can send messages
setTextFieldEditable( true );
do { // process messages sent from server
// read message and display it
try {
message = ( String ) input.readObject();
displayMessage( "\n" + message );
}
// catch problems reading from server
catch ( ClassNotFoundException classNotFoundException ) {
displayMessage( "\nUnknown object type received" );
}
Read String from
client and display it
} while ( !message.equals( "SERVER>>> TERMINATE" ) );
} // end method processConnection
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// close streams and socket
private void closeConnection()
{
displayMessage( "\nClosing connection" );
setTextFieldEditable( false ); // disable enterField
try {
output.close();
input.close();
client.close();
}
catch(
catch( IOException ioException ) {
ioException.printStackTrace();
}
Method
closeConnection
closes streams and
sockets
}
// send message to server
private void sendData( String message )
{
// send object to server
try {
output.writeObject( "CLIENT>>> " + message );
output.flush();
displayMessage( "\nCLIENT>>> " + message );
}
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Method flush
empties output buffer
and sends header
information
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// process problems sending object
catch ( IOException ioException ) {
displayArea.append( "\nError writing object" );
}
}
// utility method called from other threads to manipulate
// displayArea in the eventevent-dispatch thread
private void displayMessage( final String messageToDisplay )
{
// display message from GUI thread of execution
SwingUtilities.invokeLater(
new Runnable() { // inner class to ensure GUI updates properly
public void run() // updates displayArea
{
displayArea.append( messageToDisplay );
displayArea.setCaretPosition(
displayArea.getText().length() );
}
}
// end inner class
); // end call to SwingUtilities.invokeLater
}
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// utility method called from other threads to manipulate
// enterField in the eventevent-dispatch thread
private void setTextFieldEditable( final boolean editable )
{
// display message from GUI thread of execution
SwingUtilities.invokeLater(
new Runnable() { // inner class to ensure GUI updates properly
public void run() // sets enterField's editability
{
enterField.setEditable( editable );
}
}
// end inner class
); // end call to SwingUtilities.invokeLater
}
public static void main( String args[] )
{
Client application;
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if ( args.length == 0 )
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application = new Client( "127.0.0.1" );
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application = new Client( args[ 0 ] );
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application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE
JFrame.EXIT_ON_CLOSE );
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application.runClient();
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}
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212 } // end class Client
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Create a client to
connect to the localhost
Connect to a host
supplied by the user
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Exercício
• Estabeleça um chat com um colega
através da porta 8189.
Paulo André Castro
CES-22
IEC - ITA
6.3 Reading a File on a Web Server
• Swing GUI component JEditorPane
– Can display simple text and HTML formatted text
– Can be used as a simple Web browser
• Retrieves files from a Web server at a given URI
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CES-22
IEC - ITA
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// ReadServerFile.java
// Use a JEditorPane to display the contents of a file on a Web server.
import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
import javax.swing.event.*;
public class ReadServerFile extends JFrame {
private JTextField enterField;
private JEditorPane contentsArea;
// set up GUI
public ReadServerFile()
{
super(
super( "Simple Web Browser" );
File displayed in
JEditorPane
Container container = getContentPane();
// create enterField and register its listener
enterField = new JTextField( "Enter file URL here" );
enterField.addActionListener(
new ActionListener() {
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CES-22
IEC - ITA
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// get document specified by user
public void actionPerformed( ActionEvent event )
{
getThePage( event.getActionCommand() );
}
} // end inner class
); // end call to addActionListener
container.add( enterField, BorderLayout.NORTH
BorderLayout.NORTH );
// create contentsArea and register HyperlinkEvent
contentsArea = new JEditorPane();
contentsArea.setEditable( false );
contentsArea.addHyperlinkListener(
new HyperlinkListener() {
Register a
HyperlinkListener to
listener
handle HyperlinkEvents
// if user clicked hyperlink, go to specified page
public void hyperlinkUpdate( HyperlinkEvent event )
{
if ( event.getEventType() ==
HyperlinkEvent.EventType.ACTIVATED
HyperlinkEvent.EventType.ACTIVATED )
getThePage( event.getURL().toString() );
}
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Method
hyperlinkUpdate
called when hyperlink
clicked
Determine type of
hyperlink
Get URL of hyperlink
and retrieve page
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IEC - ITA
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} // end inner class
); // end call to addHyperlinkListener
container.add( new JScrollPane( contentsArea ),
BorderLayout.CENTER
BorderLayout.CENTER );
setSize( 400,
400, 300 );
setVisible( true );
} // end constructor ReadServerFile
// load document
private void getThePage( String location )
{
// load document and display location
try {
contentsArea.setPage( location );
enterField.setText( location );
}
catch ( IOException ioException ) {
JOptionPane.showMessageDialog( this,
this,
"Error retrieving specified URL",
URL", "Bad URL",
URL",
JOptionPane.ERROR_MESSAGE
JOptionPane.ERROR_MESSAGE );
}
Method setPage
downloads document
and displays it in
JEditorPane
} // end method getThePage
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CES-22
IEC - ITA
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public static void main( String args[] )
{
ReadServerFile application = new ReadServerFile();
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
}
} // end class ReadServerFile
Paulo André Castro
CES-22
IEC - ITA
Exercício
• Incluir um barra de ferramentas acima do
campo de edição da URL com os botões
“Home” (Página Inicial) e “Atualizar” e
seus respectivos comportamentos
• Criar botão “Voltar” e seu respectivo
comportamento
Paulo André Castro
CES-22
IEC - ITA
Desafio
• Criar novas versões das classes de Client e Server do
package ClientServer tais que seja possível estabelecer
um chat com múltiplos clientes. Cada cliente deve ser
identificado Client1, client2,etc. de acordo com a ordem
de conexão ao servidor.
• Ao ser enviado mensagem de um cliente qualquer todos
os clientes e servidor devem receber tal mensagem com
a identificação ClientX>>>
• O servidor não precisa ter uma interface gráfica
Paulo André Castro
CES-22
IEC - ITA