Java Techwars

Wednesday, 19 June 2013

JSP Tutorial for Beginner Part I

JSP Tutorial for Beginner

Jsp Tutorial for Beginner

What is jsp ?

Jsp is easiest and powerful scripting language because it is compiled by web container/servlet container.

Jsp is used to create dynamic web pages for the interaction of end user with the help of jsp form or html form.

Jsp is provided by sun Microsystems. Jsp is first compiled and then make servlet. Jsp takes request from

Browser and process this request by web server and response send back to browser.

JSP code can be put inside HTML code. Both code work together, JSP code be embedded with scriptlet <% inside this jsp code %>

JSP setup and Installation

Jsp need any web server like weblogic, Websphere, tomcat. All jsp should be deployed into web server

We will use Tomcat server to run JSP, this Tomcat server can run on any platform like windows or linux.

First Install tomcat and deploy jsp in tomcat container as the following directory structure

Tomcat
   Bin
   Conf
   Lib
   Logs
   Tmp
+Webapps
        Doc
        Example
        File
        Host-manager
        ROOT
        jsp
  +Work
        Catalina

We will use our own application context, so have to make our own folder in webapps folder with jsp name. All jsp file should be copy in this jsp folder.

JSP forms and User Input

JSP form is a way to interact with user input with web server or database server. In this, HTML form tag (e.g <input type=”text” name=”name”>, <input type=”password” name=”name”>, <input type=”radio” name=”name”>, <input type=”checkbox” name=”name”>) is used and values inside this form tag can be retrieved by request objects of JSP engine.

JSP Example of input text form

Html.jsp :

<%@ page contentType="text/html; charset=iso-8859-1" language="java" %>

<html>

<body>

<form name="frm" method="get" action="textInput.jsp">

<table width="100%" border="0" cellspacing="0" cellpadding="0">

<tr>

</tr>

<tr>

<td>Name Student </td>

</tr>

 <tr>

    <td>Active <input type="radio" name="active" value="Active"></td>

    <td>DeActive <input type="radio" name="active" value="DeActive"></td>

  </tr>

 <tr>

    <td>State <input type="checkbox" name="state" value="state"></td>

    <td>City <input type="checkbox" name="city" value="city"></td>

  </tr>

<tr>

</tr>

<tr>

</tr>

</table>

</form>

</body>

</html>

Get these form value in JSP

textInput.jsp

<%@ page contentType="text/html; charset=iso-8859-1" language="java" %>

<%

String studentNameInJSP=request.getParameter("studentName");

String radioInJSP=request.getParameter("active");

String checkboxStateInJSP=request.getParameter("state");

String checkboxCityInJSP=request.getParameter("city");

%>

<html>

<body>

Value of input text box in JSP : <%=studentNameInJSP%>

Value of checkbox in JSP : <%=checkboxStateInJSP%> <%=checkboxCityInJSP%>

Value of radio button box in JSP : <%=radioInJSP%>

</body>

</html>

Form Validation using javascript in jsp

formValidation.jsp

<%@ page contentType="text/html; charset=iso-8859-1" language="java" %>

<html>

<head>

<script>

function validateForm()

    if(document.frm.username.value=="")

      alert("User Name should be left blank");

      document.frm.username.focus();

      return false;

    else if(document.frm.pwd.value=="")

      alert("Password should be left blank");

      document.frm.pwd.focus();

      return false;

</script>

</head>

<body>

<form name="frm" method="get" action="validateInput.jsp" onSubmit="return validateForm()">

<table width="100%" border="0" cellspacing="0" cellpadding="0">

  <tr>

    <td width="22%">&nbsp;</td>

    <td width="78%">&nbsp;</td>

    </tr>

  <tr>

    <td>UserName </td>

    <td><input type="text" name="username" /></td>

  </tr>

  <tr>

    <td>Password</td>

    <td><input type="text" name="pwd" /></td>

  </tr>

  <tr>

    <td>&nbsp;</td>

    <td><input type="submit" name="submit" value="Submit"></td>

    </tr>

  <tr>

    <td>&nbsp;</td>

    <td>&nbsp;</td>

    </tr>

</table>

</form>

</body>

</html>

When we submit this form to web server, first it will check and validate. onSubmit="return validateForm()" event check validateForm() function in javascript, and if any field find blank it will throw error alert on browser. This submit only when validateForm() function return true. This results in jump to next form validateInput.jsp of JSP page.

What is cookie

Cookie is a small data file reside in user’s system. Cookie is made by web server to identify users. When user do any request send to web server and web server know information of user by these cookie. After process request, web server response back to request by knowing through this cookie. JSP provides cookie classes, javax.servlet.http.Cookie, by this classes we can create and retrieve cookie. Once we set value in cookie, it lived until cookie gets expired. Cookie plays a big role in session, because maximum session is tracked by cookie in JSP.

1. JSP Example of creating Cookie

createCookie.jsp

<%@ page contentType="text/html; charset=iso-8859-1" language="java" %>

<html>

<body>

<form name="frm" method="get" action="createNewCookie.jsp">

<table width="100%" border="0" cellspacing="0" cellpadding="0">

  <tr>

    <td width="22%">&nbsp;</td>

    <td width="78%">&nbsp;</td>

    </tr>

  <tr>

    <td>Cookie value Set </td>

    <td><input type="text" name="cookieSet" /></td>

  </tr>

  <tr>

    <td>&nbsp;</td>

    <td>&nbsp;</td>

  </tr>

  <tr>

    <td>&nbsp;</td>

    <td><input type="submit" name="submit" value="Submit"></td>

    </tr>

  <tr>

    <td>&nbsp;</td>

    <td>&nbsp;</td>

    </tr>

</table>

</form>

</body>

</html>

createNewCookie.jsp

<%@ page language="java" import="java.util.*"%>

<%

String cookieSet=request.getParameter("cookieSet");

Cookie cookie = new Cookie ("cookieSet",cookieSet);

response.addCookie(cookie);

%>

<html>

<head>

<title>Cookie Create Example</title>

</head>

<body>

<%

   Cookie[] cookies = request.getCookies();

    for (int i=0; i<cookies.length; i++) {

      out.println(cookies[i].getName()+" : "+cookies[i].getValue()+"<br/>");

%>

</body>

</html>

Cookie cookie = new Cookie ("cookieSet",cookieSet);

We are creating new object of cookie class.Here
new Cookie(“Key”, “value”);

Then we are adding in cookie of response object. response.addCookie(cookie); This is adding in cookie object new data.

Expire JSP cookie

Cookie cookie = new Cookie ("cookieSet",cookieSet);

cookie setMaxAge(0);

This will expire cookie.,with 0 second. We can set cookie age who long is reside for user.

Retrieve cookie from JSP

Cookie is in array object, we need to get in request.getCookies() of array.

Cookie[] cookies = request.getCookies();

for (int i=0; i<cookies.length; i++) {
out.println(cookies[i].getName()+" : "+cookies[i].getValue()+"<br/>");
}

JSP session Object

Session object is medium to interact with client and server. Session is a connection between user and server, involving exchange of information between user’s computer and server. Server knows information about each other by these session object. Web server put information of user in session object and whenever it needs information gets it from these session objects. This session object stores information in key value pair, just like hashtable. Today programming without session cannot thinkable. Most of web application is user based, somewhat use transaction (credit card, database transaction), shopping cart, email, and this needs session. Web server should know who is doing this transaction. This session object helps to differentiate users with each other, and increase application’s security. Every user have unique session, server exchange information with session objects until it get expired or destroyed by web server.

When JSP Session use

Mostly session is work with user base application, when login screen is used then set session if login is successful. It set for maximum time provided by web server or defined by application.

When JSP Session destroys

When user has done their work and want to close browser, it should be expire or destroy forcefully by user, ensure no other person can use his session.

JSP Store and Retrieve Session Variables

JSP Example of Creating session and retrieving session

session.jsp

Output

<%@ page contentType="text/html; charset=iso-8859-1" language="java" %>

<html>

<body>

<form name="frm" method="get" action="sessionSetRetrieve.jsp">

<table width="100%" border="0" cellspacing="0" cellpadding="0">

<tr>

</tr>

<tr>

<td>Session value Set </td>

</tr>

<tr>

</tr>

<tr>

</tr>

<tr>

</tr>

</table>

</form>

</body>

</html>

sessionSetRetrieve.jsp

Output

<%@ page language="java" import="java.util.*"%>

String sessionSet=request.getParameter("sessionVariable");

session.setAttribute("MySession",sessionSet);

/// String getSessionValue= (String)session.getAttribute("sessionSet");

//this is use for session value in String data

<html>

<head>

<title>Cookie Create Example</title>

</head>

<body>

Session : <%=(String)session.getAttribute("MySession")%>

</body>

</html>

session.setAttribute("MySession",sessionSet) this is use to set new session variable. If we need to retrieve session variable, have to use session.getAttribute. In this we have to get it by session variable name here we are using MySession is session variable as key.

session.setMaxInactiveInterval(2700);

session.setMaxInactiveInterval(2700), this use to set maximum session time. 2700 is time in number. In this period, if user don’t do anything session get expired automatically.

Remove JSP Session Variables or Expire JSP Session

When session is no long needed, should be removed forcefully by user. This can be done by calling session method of invalidate method session.invalidate();

session.invalidate();

This method expires session for current user, who request for log out.

New session can be find by isNew() method of session, when first time session is created, that is new session.

session.isNew();

Monday, 17 June 2013

Pagination in JSP and Servlet

Pagination in JSP and Servlet

What is Pagination ?

Fetching millions of records from database consumes almost all CPU power and memory of machine.
Hence we break millions of records into small chunks showing limited number of records (say 10 or 20) per page. The best example of this is Google search pagination which allows user to navigate to next page by page number and explore limited records per pages.

Steps for creating pagination in jsp and servlet.

Step 1 : First You have to create employee table in mysql database.

The structure of employee table is as

CREATE TABLE `employee` (
  `emp_id` int(10) NOT NULL,
  `emp_name` varchar(50) DEFAULT NULL,
  `salary` double DEFAULT NULL,
  `department` varchar(50) DEFAULT NULL,
  `state` varchar(50) DEFAULT NULL,
  `city` varchar(50) DEFAULT NULL,
  `country` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`emp_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Step 2 : Download mysql connector and jstl jar and include in WEB-INF/lib folder

Step 3 : Writing transfer object class as Employee

package test.paging;

public class Employee {

private int id;

private String name;

private double salary;

private String department;

private String state;

private String city;

private String country;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public double getSalary() {

return salary;

}

public void setSalary(double salary) {

this.salary = salary;

}

public String getDepartment() {

return department;

}

public void setDepartment(String department) {

this.department = department;

}

public String getState() {

return state;

}

public void setState(String state) {

this.state = state;

}

public String getCity() {

return city;

}

public void setCity(String city) {

this.city = city;

}

public String getCountry() {

return country;

}

public void setCountry(String country) {

this.country = country;

}

Step 4 : Writing Connection Factory Class

package test.paging;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

public class ConnectionFactory {

//static reference to itself

private static ConnectionFactory instance =new ConnectionFactory();

String url = "jdbc:mysql://localhost/test";

String user = "root";

String password = "admin1&$$31223";

String driverClass = "com.mysql.jdbc.Driver";

//private constructor

private ConnectionFactory() {

try {

Class.forName(driverClass);

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

public static ConnectionFactory getInstance() {

return instance;

}

public Connection getConnection() throws SQLException,ClassNotFoundException {

Connection connection =DriverManager.getConnection(url, user, password);

return connection;

}

Step 5 : Writing DAO Class

package test.paging;

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import java.util.List;

public class EmployeeDAO {

Connection connection;

Statement stmt;

private int noOfRecords;

public EmployeeDAO() {

}

private static Connection getConnection() throws SQLException,ClassNotFoundException {

Connection con = ConnectionFactory.getInstance().getConnection();

return con;

}

public List<Employee> viewAllEmployees(int offset,int noOfRecords)

{

String query = "select SQL_CALC_FOUND_ROWS * from employee limit "+ offset + ", " + noOfRecords;

System.out.println("EmployeeDAO.viewAllEmployees()"+query);

List<Employee> list = new ArrayList<Employee>();

Employee employee = null;

try {

connection = getConnection();

stmt = connection.createStatement();

ResultSet rs = stmt.executeQuery(query);

while (rs.next()) {

employee = new Employee();

employee.setId(rs.getInt("emp_id"));

employee.setName(rs.getString("emp_name"));

employee.setSalary(rs.getDouble("salary"));

employee.setDepartment(rs.getString("department"));

employee.setState(rs.getString("state"));

employee.setCity(rs.getString("city"));

employee.setCountry(rs.getString("country"));

list.add(employee);

}

rs.close();

rs = stmt.executeQuery("SELECT FOUND_ROWS()");

if(rs.next())

this.noOfRecords = rs.getInt(1);

} catch (SQLException e) {

e.printStackTrace();

} catch (ClassNotFoundException e) {

e.printStackTrace();

}finally

{

try {

if(stmt != null)

stmt.close();

if(connection != null)

connection.close();

} catch (SQLException e) {

e.printStackTrace();

}

return list;

}

public int getNoOfRecords() {

return noOfRecords;

}

Step 6 : Writing Servlet :

package test.paging;

import java.io.IOException;

import java.util.List;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class EmployeeServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

public EmployeeServlet() {

super();

}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

int page = 1;

int recordsPerPage = 5;

if(request.getParameter("page") != null){

page = Integer.parseInt(request.getParameter("page"));

}

EmployeeDAO dao = new EmployeeDAO();

List<Employee> list = dao.viewAllEmployees((page-1)*recordsPerPage,recordsPerPage);

int noOfRecords = dao.getNoOfRecords();

int noOfPages = (int) Math.ceil(noOfRecords * 1.0 / recordsPerPage);

request.setAttribute("employeeList", list);

request.setAttribute("noOfPages", noOfPages);

request.setAttribute("currentPage", page);

RequestDispatcher view = request.getRequestDispatcher("display.jsp");

view.forward(request, response);

}

Step 7 : Writing web.xml as

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javae

/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

<display-name>JSPPagination</display-name>

<servlet-name>EmployeeServlet</servlet-name>

<servlet-class>test.paging.EmployeeServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>EmployeeServlet</servlet-name>

<url-pattern>/employee.do</url-pattern>

</servlet-mapping>

</web-app>

Step 8 : Writing display.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"

"http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Employees</title>

</head>

<body>

<tr>

<th>Employee ID</th>

<th>Empployee Name</th>

<th>Salary</th>

<th>Department</th>

<th>State</th>

<th>Country</th>

</tr>

<c:forEach var="employee" items="${employeeList}">

<tr>

<td>${employee.id}</td>

<td>${employee.name}</td>

<td>${employee.salary}</td>

<td>${employee.department}</td>

<td>${employee.state}</td>

<td>${employee.city}</td>

<td>${employee.country}</td>

</tr>

</c:forEach>

</table>

<td>

<%--For displaying Previous link except for the 1st page --%>

<c:if test="${currentPage != 1}">

<a href="employee.do?page=${currentPage - 1}"> Previous</a>

</c:if>

<%--For displaying Page numbers.

The when condition does not display a link for the current page--%>

<c:forEach begin="1" end="${noOfPages}" var="i">

<c:choose>

<c:when test="${currentPage eq i}">

${i}

</c:when>

<c:otherwise>

<a href="employee.do?page=${i}">${i} </a>

</c:otherwise>

</c:choose>

</c:forEach>

<%--For displaying Next link --%>

<c:if test="${currentPage lt noOfPages}">

<a href="employee.do?page=${currentPage + 1}"> Next</a>

</c:if>

</td>

</table>

</body>

</html>

Step 9 : Deploy all files in tomcat container

Step 10 : Start the tomcat

Step 11 : Access the page in browser

http://localhost:8080/paging/employee.do

Step 12 : The Output are :

Employee ID	Empployee Name	Salary	Department	State	City	Country
6	shyama	72363.0	media sales	up	bihar	india
7	rahima	387483.0	techops	up	bihar	india
8	rahima	387483.0		up		india
9	rahima	387483.0		up		india
10	rahima	387483.0		up		india

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Thanks & Regards

Friday, 14 June 2013

How To Access Private Members of a Java class using Reflection

How To Access Private Members of a Java class using Reflection.

java.lang.reflect package provides the AccessibleObject class that is parent class of Constructor, Method, and Field class. Using the AccessibleObject class, we can change the access control flags of a Reflection Object (Reflection is a feature in the Java programming language. It allows an executing Java program to examine or “introspect” upon itself, and manipulate internal properties of the program. For example, it’s possible for a Java class to obtain the names of all its members and display them.), and the setAccessible(boolean)method is used to change the access control flag of an Object.

For Example :

package test;

public class PrivateAccessMember {

private int privateInt = 10;

private String privateString = "temp String";

private long privateLong = 1234567890L;

private void resetFields(int i, String s, long l) {

privateInt = i;

privateString = s;

privateLong = l;

}

public void display() {

System.out.println("Int = " + privateInt);

System.out.println("String = " + privateString);

System.out.println("Long = " + privateLong);

}

package test;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

public class TestPrivateMember {

public static void main(String[] args) {

PrivateAccessMember obj = new PrivateAccessMember();

obj.display();

Class clazz = obj.getClass();

try {

Field intField = clazz.getDeclaredField("privateInt");

Field strField = clazz.getDeclaredField("privateString");

Field longField = clazz.getDeclaredField("privateLong");

intField.setAccessible(true);

strField.setAccessible(true);

longField.setAccessible(true);

System.out.println("value of privateInt field is : " + intField.get(obj));

System.out.println("value of privateString field is : " + strField.get(obj));

System.out.println("value of privateLong field is : " + longField.get(obj));

intField.set(obj, 100);

strField.set(obj, "this is new string");

longField.set(obj, 55555L);

obj.display();

} catch (SecurityException e) {

e.printStackTrace();

} catch (NoSuchFieldException e) {

e.printStackTrace();

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

try {

Method method = clazz.getDeclaredMethod("resetFields", int.class, String.class, long.class);

method.setAccessible(true);

method.invoke(obj, 25, "new String from resetField method.", 987654321L);

obj.display();

} catch (SecurityException e) {

e.printStackTrace();

} catch (NoSuchMethodException e) {

e.printStackTrace();

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

} catch (InvocationTargetException e) {

e.printStackTrace();

}

The Output are :

Int = 10

String = temp String

Long = 1234567890

value of privateInt field is : 10

value of privateString field is : temp String

value of privateLong field is : 1234567890

Int = 100

String = this is new string

Long = 55555

Int = 25

String = new String from resetField method.

Long = 987654321

Friday, 7 June 2013

Restore Mysql Database by Physical files

Restore Mysql Database by Physical files

When you want to move whole database schema and data, then you

Follows the following steps

Step 1 : Stop the database on server you want to move database.

Step 2 : Go to the directory where mysql data are ie data dir

Step 3 : Transfer over the folder (and its contents) over to the new server's mysql data directory

Step 4 : Start back up the database. And then start the mysql server

Step 5 : On the new server, issue a 'create database' command.'

Step 6 : Re-create the users & grant permissions.

For existing user from old server

grant all privileges on *.* to root@'%' identified by 'admin123';

flush privileges;

GRANT ALL PRIVILEGES ON *.* TO 'username'@'%' WITH GRANT OPTION;

If you want to move database with replication then you have to move physical files

From master to new server 1 and replica to new replication server 2

Check all is working fine, then you have to configure

Replication for master to slave on new servers

The second way to restore the database to new server is pipe a mysqldump command to a sql command, You can do all databases or a specific one. So, for instance,

mysqldump -uuser -ppassword myDatabase | mysql -hremoteserver -uremoteuser -premoteserver

You can do all databases with

mysqldump --all-databases -uuser -ppassword | mysql -hremoteserver -uremoteuser -premoteserver

If you just want to move a specific table try:

mysqldump -u username -ppassword databasename tablename > databasename.tablename.sql

You can specify more table names above, in the same command. Once the command completes, move the databasename.tablename.sql file to the other server and then restore using:

mysql -u username -ppassword databasename < databasename.tablename.sql

Thursday, 6 June 2013

How to install and configure FileZilla FTP server on windows

1. Download from following link.

https://filezilla-project.org/

2. Run the exe installer

3. Select admin port and remember this port

4. Launch FileZilla Server Interface

5. Enter port from above, enter (new) password for administration, click ok/connect

6. Create a user and/or group with permissions to a home directory.

7. Add additional directory and set the alias name to display within home directory (e.g. /AliasName)

Setup Firewall in Windows 2008
=====================

1. Open "Windows Firewall with Advanced Security"

2. Click "New Rule" in right pane under "Inbound Rules"

3. Select Program and click "Next"

4. Browse C:\Program Files (x86)\FileZilla Server\FileZilla server.exe and click "Next"

5. Choose "Allow the connection" and click "Next"

6. Choose Domain, Private & Public and cli ck "Next"

7. Give name as "Filezilla Server Ports" and click "Finish"

Setup Firewall in Windows 2003
=====================

1. Open Control panel

2. Click "Windows Firewall"

3. Click "Exceptions" Tab

4. Click "Add Programs"

5. Browse C:\Program Files\FileZilla Server\FileZilla server.exe

==================================================

1 : Open FileZilla Client on client machine
2 : Put Hostname, username,password,port
3 : Click quickconnect button
4 : After Successful connection
5 : Download/Upload files