JAVA EE: June 2014

Saturday, 28 June 2014

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JDBC : Steps to Connect to the Database

See also:

Servlets Tutorial

All Design Patterns Links

JDBC Tutorial

Servlets : HTTP Status Codes

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HTTP Status Codes

See also:

Servlets Tutorial

All Design Patterns Links

Servlets : SingleThreadModel

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SingleThreadModel

See also:

Servlets Tutorial

All Design Patterns Links

Servlets : Hidden Form Field

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See also:

Servlets Tutorial

All Design Patterns Links

Servlets : URL Rewriting

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See also:

Servlets Tutorial

All Design Patterns Links

Sunday, 22 June 2014

Servlets : User Authorization

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User Authorization

See also:

Servlets Tutorial

All Design Patterns Links

Saturday, 21 June 2014

Servlets : HttpSession Listener Demo [Count logged in Users]

Click here to watch in Youtube : https://www.youtube.com/watch?v=fv8Idtevcg0

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HttpSessionListenerDemo Project Dir Structure

LoginServlet.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet
{
    
    private static final long serialVersionUID = 1L;

    public void init() throws ServletException
    {
        System.out.println("-----------------------------------------");
        System.out.println(" Init method is called in "
                + this.getClass().getName());
        System.out.println("--------------------------------------");
    }
    
    public void doGet( HttpServletRequest request, HttpServletResponse response )
            throws ServletException, IOException
    {

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        String userName = request.getParameter("username");
        out.print("Welcome " + userName);

        HttpSession session = request.getSession();
        session.setAttribute("uname", userName);

        ServletContext ctx = getServletContext();
        int totalUsers = (Integer) ctx.getAttribute("totalusers");
        int currentUsers = (Integer) ctx.getAttribute("currentusers");
        
        out.print("<br>total users= " + totalUsers);
        out.print("<br>current users= " + currentUsers);

        out.print("<br><a href='logout'>logout</a>");

        out.close();
    }
    
    public void destroy()
    {
        System.out.println("-----------------------------------------");
        System.out.println(" destroy method is called in "
                + this.getClass().getName());
        System.out.println("-----------------------------------------");
    }

}

LogoutServlet.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LogoutServlet extends HttpServlet
{

    private static final long serialVersionUID = 1L;

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

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        HttpSession session = request.getSession(false);
        session.invalidate();

        out.print("You are successfully logged out");

        out.close();
    }

}

CountUserListener.java

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class CountUserListener implements HttpSessionListener
{
    ServletContext ctx = null;
    static int     totalUserCount = 0, currentUserCount = 0;

    public void sessionCreated( HttpSessionEvent httpSessionEvent )
    {
        System.out.println("sessionCreated method has been called in "
                + this.getClass().getName());

        
        totalUserCount++;
        currentUserCount++;

        ctx = httpSessionEvent.getSession().getServletContext();
        
        ctx.setAttribute("totalusers", totalUserCount);
        ctx.setAttribute("currentusers", currentUserCount);

    }

    public void sessionDestroyed( HttpSessionEvent httpSessionEvent )
    {
        
        System.out.println("sessionDestroyed method has been called in "
                + this.getClass().getName());       
        currentUserCount--;
        ctx.setAttribute("currentusers", currentUserCount);
    }

}

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    metadata-complete="true" version="3.0">
    <display-name>HttpSessionListenerDemo</display-name>
    <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>


    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>LoginServlet</servlet-class>
    </servlet>
    
    <servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>LogoutServlet</servlet-class>
    </servlet>


    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/logout</url-pattern>
    </servlet-mapping>


    <listener>
        <listener-class>CountUserListener</listener-class>
    </listener>
    
</web-app>

index.html

<form action="login">
    Name:<input type="text" name="username"><br> 
    
    Password:<input type="password" name="password"><br> 
    
    <input type="submit" value="login" />
    
</form>

Environment Used

JDK version :1.7.0_51
Tomcat version : 7.0.50

To Download HttpSessionListenerCountUserDemoApp Project Click the below link

https://sites.google.com/site/javaee4321/servlets/HttpSessionListenerCountUserDemoApp.zip?attredirects=0&d=1

See also:

Servlets Tutorial

All Design Patterns Links

Servlets Listeners

Click here to watch in Youtube : https://www.youtube.com/watch?v=7NtVn1_TSAg

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Servlets Listeners

See also:

Servlets Tutorial

All Design Patterns Links

Servlets : HttpSessionBindinglistener Demo

Click here to watch in Youtube : https://www.youtube.com/watch?v=DquotVucWWQ

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HttpSessionBindingListenerDemo Project Dir Structure

HttpSessionAttributeTestServlet.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class HttpSessionAttributeTestServlet extends HttpServlet
{
    private static final long serialVersionUID = 1L;

    public void init() throws ServletException
    {
        System.out.println("-----------------------------------------");
        System.out.println(" Init method is called in "
                + this.getClass().getName());
        System.out.println("--------------------------------------");
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        HttpSession httpSession = request.getSession();

        sleep();

        User user = new User("Ram", 43);
        httpSession.setAttribute("userinfo", user);

        sleep();

        httpSession.invalidate();

        out.println("This is the example of HttpSessionBindingListener");

    }

    private void sleep()
    {
        try
        {
            Thread.sleep(10000);
        }
        catch (InterruptedException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void destroy()
    {
        System.out.println("-----------------------------------------");
        System.out.println(" destroy method is called in "
                + this.getClass().getName());
        System.out.println("-----------------------------------------");
    }

}

User.java

import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

public class User implements HttpSessionBindingListener
{

    private String name;
    private int age;

    public User(String name, int age)
    {
        super();
        this.name = name;
        this.age = age;
    }

    public User(String name)
    {
        this.name = name;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public int getAge()
    {
        return age;
    }

    public void setAge(int age)
    {
        this.age = age;
    }

    @Override
    public void valueBound(HttpSessionBindingEvent httpSessionBindingEvent)
    {
        System.out.println("\n###################################\n");

        System.out.println("valueBound method has been called in "
                + this.getClass().getName());

        System.out.println("Added/Replaced Attribute Name ="
                + httpSessionBindingEvent.getName() + ",value = "
                + httpSessionBindingEvent.getValue());

        System.out.println("\n#####################################\n");

        /*
         * if particular Attribute is added/replaced, based on that if you want
         * to perform any operation then you can do it here.
         */

    }

    @Override
    public void valueUnbound(HttpSessionBindingEvent httpSessionBindingEvent)
    {
        System.out.println("\n###################################\n");

        System.out.println("valueUnbound method has been called in "
                + this.getClass().getName());

        System.out.println("Removed Attribute Name ="
                + httpSessionBindingEvent.getName() + ",value = "
                + httpSessionBindingEvent.getValue());

        System.out.println("\n#####################################\n");

        /*
         * if particular Attribute is removed, based on that if you want to
         * perform any operation then you can do it here.
         */

    }

    @Override
    public String toString()
    {
        return "User [name=" + name + ", age=" + age + "]";
    }

}

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    metadata-complete="true" version="3.0">

    <display-name>HttpSessionBindingListenerDemo</display-name>

    <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>

    <servlet>
        <servlet-name>HttpSessionAttributeTestServlet</servlet-name>
        <servlet-class>HttpSessionAttributeTestServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HttpSessionAttributeTestServlet</servlet-name>
        <url-pattern>/listenerTest</url-pattern>
    </servlet-mapping>

</web-app>

index.html

<html>
<body>
    <a href="listenerTest">listenerTest</a>
</body>
</html>

Environment Used

JDK version :1.7.0_51
Tomcat version : 7.0.50

To Download HttpSessionBindingListenerDemoApp Project Click the below link

https://sites.google.com/site/javaee4321/servlets/HttpSessionBindingListenerDemoApp.zip?attredirects=0&d=1

See also:

Servlets Tutorial

All Design Patterns Links