ඔන්න Java EE ඉගන ගන්න අයට Java Networking/ RMI / Socket Programming වැදගත් කොටස් කිහිපයක විස්කරයක් කරන්නයි යන්නෙ ගවේෂක අද.
Java Networking
In java networking we can divide it into two categories and let's see the comparision
- Stream Based(TCP)
- Connection based
- Reliable
- Packet Based(UDP)
- Connectionless
- Not Reliable
Establish a simple Server using Stram Socket
1.Server Socket
ServerSocket server=new ServerSocket (Port_Number,Queue_Lengh);
2.Accept Client
Socket Connection=Server.accept();
3.Open Path
Input and OutPut Stream
4.Processing Part
Communication
5.Server Close
************************************************************************
Client/Server Communication Process Using TCP
- Server issues a call to create a listening socket.
- Server and client create a socket.
- Server and client bind socket. (This step is optional for a client.)
- Server converts an unconnected socket into a passive socket (LISTEN state).
- Server issues an accept() and process blocks waiting for a connection request.
- Client sends a connection request.
- Server accepts the connection; a new socket is created for communication with this client.
- Server receives device information from the local host.
- Data exchange takes place.
- Client and server delete the socket.
- Server deletes the listener socket when the service to the client is terminated.
UDP Socket Communication Process
- Server and client create a socket.
- Server and client bind the socket name.
- Data exchange takes place.
- Server and client delete the socket.
Port Vs Socket(Referenced)
A port is a logical connection method two end points communicate with. Ports operate at the Transport layer of the OSI.
A TCP socket is not a connection, it is the endpoint of a specific connection.
There can be concurrent connections to a service endpoint, because a connection is identified by both its local and remote endpoints, allowing traffic to be routed to a specific service instance.
Sockets are a means of plugging the application layer in. Sockets are determined by an IP address and port number.A socket is one end point of a connection.
A socket consists of three things:
- An IP address
- A transport protocol
- A port number
A port is a number between 1 and 65535 inclusive that signifies a logical gate in a device. Every connection between a client and server requires a unique socket.
For example:
- 1030 is a port.
- (10.1.1.2 , TCP , port 1030) is a socket.
A port is a virtualisation identifier defining a service endpoint (as distinct from a service instance endpoint aka session identifier).
A TCP socket is an endpoint instance defined by an IP address and a port in the context of either a particular TCP connection or the listening state.
There can only be one listener socket for a given address/port combination.
Java Remote Method Invocation
Steps of RMI
- Make sure there is these classes are available
- Serializable Classes
- Remote Classes and Interfaces
- Should be as follow the programming part order
- Programming a client
- Programming a server
- Finally Runing the programme should be as follows
Codings
Hello.java
import java.rmi.server.*;
import java.rmi.*;
public class Hello extends UnicastRemoteObject implements HelloInterface{
public String message;
public Hello(String msg) throws RemoteException{
message=msg;
}
public void login(String name, String pass) throws RemoteException{
}
public void logout(String name) throws RemoteException{
}
public String chat(String name, String msg) throws RemoteException{
return message;
}
}
HelloClient.java
import java.rmi.*;
public class HelloClient{
public static void main(String[] arg){
try{
HelloInterface hello = (HelloInterface)Naming.lookup("//localhost:1099/Hello");
hello.login("Lahiru","123");
System.out.println(hello.chat("Lahiru","Hi!!!"));
}catch(Exception e){
System.out.println("Exception :"+e.getMessage());
}
}
}
HelloServer.java
import java.rmi.*;
import java.io.*;
public class HelloServer{
public static void main(String[] arg){
try{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Login Name: ");
String name = br.readLine();
Naming.rebind("Hello", new Hello(name));
System.out.println("Hello Server Ready");
}catch(Exception e){
System.out.println("Exception "+e);
}
}
}
HelloInterface.java
import java.rmi.*;
public interface HelloInterface extends Remote{
public void login(String name, String pass) throws RemoteException;
public void logout(String name) throws RemoteException;
public String chat(String name, String pass) throws RemoteException;
}
Regular Expressions
| Regular Expression | Description |
|---|
\d | Any digit, short for [0-9] |
\D | A non-digit, short for [^0-9] |
\s | A whitespace character, short for [ \t\n\x0b\r\f] |
\S | A non-whitespace character, short for [^\s] |
\w | A word character, short for [a-zA-Z_0-9] |
\W | A non-word character [^\w] |
Here is a code for email validation pattern
EmailValidator.java
package com.mkyong.regex;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class EmailValidator {
private Pattern pattern;
private Matcher matcher;
private static final String EMAIL_PATTERN =
"^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
+ "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
public EmailValidator() {
pattern = Pattern.compile(EMAIL_PATTERN);
}
/**
* Validate hex with regular expression
*
* @param hex
* hex for validation
* @return true valid hex, false invalid hex
*/
public boolean validate(final String hex) {
matcher = pattern.matcher(hex);
return matcher.matches();
}
}
For Validate a Form Entry Data
Validate.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package RegularEx;
import java.util.Scanner;
/**
*
* @author Lahiru Dhananjaya
*/
public class Validate {
public static void main(String[] args) {
ValidateInput vi=new ValidateInput();
Scanner s=new Scanner(System.in);
System.out.println("Enter First Name");
String fname=s.next();
System.out.println("Enter Last Name");
String lname=s.next();
System.out.println("Enter Address");
String address=s.next();
System.out.println("Enter City");
String city=s.next();
System.out.println("Enter State");
String state=s.next();
System.out.println("Enter Zip");
String zip=s.next();
System.out.println("Enter Phone Number");
String phone=s.next();
if(!vi.validateFirstName(fname))
{
System.out.println("Invalid First Name");
}
else if(!vi.validateLastName(lname))
{
System.out.println("Invalid Last Name");
}
else if(!vi.validateAddress(address))
{
System.out.println("Invalid Address");
}
else if(!vi.validateCity(city))
{
System.out.println("Invalid City");
}
else if(!vi.validateState(state))
{
System.out.println("Invalid State");
}
else if(!vi.validateZip(zip))
{
System.out.println("Invalid Zip");
}
else if(!vi.validatePhone(phone))
{
System.out.println("Invalid Phone");
}
else
{
System.out.println("Ok");
}
}
}
ValidateInput.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package RegularEx;
/**
*
* @author Lahiru Dhananjaya
*/
public class ValidateInput {
public static boolean validateFirstName(String firstName)
{
return firstName.matches("[A-Z][a-zA-Z]*");
}
public static boolean validateLastName(String lastName)
{
return lastName.matches("[a-zA-Z]+([ '-][a-zA-Z]*)");
}
public static boolean validateAddress(String address)
{
return address.matches("\\d+\\s+[a-zA-Z]+|[a-zA-Z]+\\s[a-zA-Z]+");
}
public static boolean validateCity(String city)
{
return city.matches("[a-zA-Z]+|[a-zA-Z]+\\s[a-zA-Z]+");
}
public static boolean validateState(String state)
{
return state.matches("[a-zA-Z]+|[a-zA-Z]+\\s[a-zA-Z]+");
}
public static boolean validateZip(String zip)
{
return zip.matches("\\d{5}");
}
public static boolean validatePhone(String phone)
{
return phone.matches("[1-9]\\d{2}-[1-9]\\d{2}-\\d{4}");
}
}
Java Bean Class Example
Edisplay.java
package xm_java_bean;
/**
*
* @author Lahiru Dhananjaya
*/
public class Edisplay {
public static void main(String[] args) {
Employee em=new Employee();
em.setName("Lahiru");
em.setNumber("001");
System.out.println(em.getName());
System.out.println(em.getNumber());
}
}
Employee.java
package xm_java_bean;
/**
*
* @author Lahiru Dhananjaya
*/
public class Employee implements java.io.Serializable {
private String EmployeeName;
private String EmployeeNumber;
//Default Constructor
public Employee() {
}
public void setName(final String EmployeeName) {
this.EmployeeName = EmployeeName;
}
public void setNumber(final String EmployeeNumber) {
this.EmployeeNumber = EmployeeNumber;
}
public String getName() {
return EmployeeName;
}
public String getNumber() {
return EmployeeNumber;
}
}
********************************************************************************
To view Full code in JSP(Referenced)
package player;
public class PersonBean implements java.io.Serializable {
/**
* Property <code>name</code> (note capitalization) readable/writable.
*/
private String name = null;
private boolean deceased = false;
/** No-arg constructor (takes no arguments). */
public PersonBean() {
}
/**
* Getter for property <code>name</code>
*/
public String getName() {
return name;
}
/**
* Setter for property <code>name</code>.
* @param value
*/
public void setName(final String value) {
name = value;
}
/**
* Getter for property "deceased"
* Different syntax for a boolean field (is vs. get)
*/
public boolean isDeceased() {
return deceased;
}
/**
* Setter for property <code>deceased</code>.
* @param value
*/
public void setDeceased(final boolean value) {
deceased = value;
}
}
TestPersonBean.java:
import player.PersonBean;
/**
* Class <code>TestPersonBean</code>.
*/
public class TestPersonBean {
/**
* Tester method <code>main</code> for class <code>PersonBean</code>.
* @param ARGS
*/
public static void main(String[] args) {
PersonBean person = new PersonBean();
person.setName("Bob");
person.setDeceased(false);
// Output: "Bob [alive]"
System.out.print(person.getName());
System.out.println(person.isDeceased() ? " [deceased]" : " [alive]");
}
}
testPersonBean.jsp;
<% // Use of PersonBean in a JSP. %>
<jsp:useBean id="person" class="player.PersonBean" scope="page"/>
<jsp:setProperty name="person" property="*"/>
<html>
<body>
Name: <jsp:getProperty name="person" property="name"/><br/>
Deceased? <jsp:getProperty name="person" property="deceased"/><br/>
<br/>
<form name="beanTest" method="POST" action="testPersonBean.jsp">
Enter a name: <input type="text" name="name" size="50"><br/>
Choose an option:
<select name="deceased">
<option value="false">Alive</option>
<option value="true">Dead</option>
</select>
<input type="submit" value="Test the Bean">
</form>
</body>
</html>
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