EJB / EE :: Preventing Multiple Logins Into Web Application Simultaneously
Mar 31, 2014
It sounds simple enough, but I'm trying to implement a mechanism to prevent the same user logging into our distributed web application simultaneously.
So, given the scenario...
- user A logs in with username A
- user B logs in with username A
I want the logging in of username A by user B to invalidate the session for username A held by user A. So if people are sharing login credentials, the last person to log in kicks everyone else out who's logged in as that user.
The big problem I have is the application is deployed in a cluster across JVMs, so sessions are shared across nodes. My thought it to introduce a session listener to then inspect a table in the database which determines whether that user logged on - the part of identifying that is pretty simple as far as I can tell. The difficult part is kicking out the first user who logged in.
So, I guess my question is - can I invalidate an http session from with an MDB? If so my logic is to implement an MDB which listens on a topic and whenever a session is created that MDB checks for sessions belonging to the same user within that JVM to invalidate them (obviously skipping the JVM the login request came in on!).
Is that even possible? Is there a simpler way to do this?
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Jan 21, 2014
Question : What would you do block a user if he fails to login in 3 consecutive attempts ?
My Answer : I will make use of Session object, so that server could identify that all 3 requests came from the same system.
Dont know if i am right .
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Jun 17, 2014
Declaring the method as static precludes one from using any sort of object oriented programming, thus the method cannot access instance fields of the object if it needs to.
I created two short classes to sort of find out what this meant, but I feel I do not understand it well enough.
Test class (main):
package votek;
public class Test {
public static void main(String[] args) {
SomeMethod();
}
public static void SomeMethod() {
Character character = new Character();
character.totalLevel = 50;
System.out.println(character.totalLevel);
}
}
Character class:
package votek;
public class Character {
private int level = 0;
public Character() {
level = 50;
}
}
OR
Does it mean that making a static method in the class with private instances will prevent the method from using the private instances?
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May 3, 2014
How does jsp create session when there're two requests coming simultaneously from the same client browser(maybe one tab maybe two tabs)?
I ask this question because it is said jsp could solve DuplicateSessionException in flex.
[URL] ....
if so, jsp would create same session(with same session id) for the two requests coming simultaneously?
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Mar 14, 2014
I would like to know how we can deploy one Web application on multiple server to share the work between them? My first thought is that we just deploy the same war file on different servers that connect to the same database. However, what will happen when a user enter something like [URL]? How can multiple servers share the same domain name and how the requests from different users are redirected to these different server?
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Mar 6, 2015
Because there's little information that actually explains application servers in the real world, For one domain at www.url.com:
- How many application servers are there if there are multiple applications hosted on this domain? Ie. url.com/app1, url.com/app2, etc.?
- How many web servers will there be?
- How would I make one physical server handle all requests for one of the above applications?
- How would one make static content a standalone application built with angularJS? Not static content served by servlets.
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Aug 30, 2014
I am using itext to create pdf files , i have filtered some records (preferably i can say around 90) which has the option to open pdf for individual record. Now I need to open all the pdf's of filtered records on a single click , without asking for a open dialogue box. How to go about this ??
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Dec 15, 2014
Create a java application that contains an array of 10 multiple-choice questions related to you favorite hobby. each question contains three answer choices. also create a parallel array that holds the correct answer to each question - A,B, or C. display each question and verify that the users enters only A,B, or C as the answere - if not, keep prompting the user until a valid response in entered. If the user responds to a question correctly, display "Correct!"; otherwise, display the correct answer is and the letter to the correct answer. After the user answer all the question, display the number of correct and incorrect answers.
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Dec 8, 2014
I have i am trying to implement tooltip through javascript, like when we click on an image link tooltip should be displayed and it should have close button/ close image to close that tooltip.like the same way i will have multiple images on page, when ever i click on the images all tooltips should be displayed on the page when ever i want to close that then only it should close through close button on tooltip.can we do it through java script or will go for jquery.
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May 5, 2015
I'm very new to Java, and I am creating a program that takes multiple user input to create one face. I have a class for the eyes, nose, lips, and headshape. For some reason, my program is not drawing the graphics. ***for question purposes, I have only included my head shape class and my test class****
my "test" class:
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class FaceTest
{
public static void main(String[] args)
{
String head = JOptionPane.showInputDialog("Would you like a circle, square, rectangle shaped head?: ");
[Code] ....
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Nov 17, 2014
convert or move standalone java thread application into Tomcat server container for accessing its JNDI services? Also is it possible to schedule this thread application in Tomcat server? is it possible to keep this app in tomcat as web application and schedule in window's scheduler.
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Mar 11, 2014
I am new to work on JNLP program. I have created a SWING program, JNLP file when i deploy the ear file i am getting 404 error. Please find the steps in details.
1.Created a dynamic web project JWStartProject in eclipse
2.Create a HelloWorld.java class under default package.
import javax.swing.*;
public class HelloWorld extends JFrame {
private static final long serialVersionUID = 4968624166243565348L;
private JLabel label = new JLabel("Hello Java Web START!");
public HelloWorld() {
super("Jave Web Start Example");
this.setSize(350, 200);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );
this.setLayout(null);
[Code] ....
Now I exported this project as JWStartProject.war contains following code.
Created Server in Websphere Admin console
Deployed this war file under the server and started.
I have added MIME types also.
I am unable to launch the application. I am getting 404 errors. May I know where I went wrong?
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Dec 18, 2013
I have a package (JAR_A) for entity and controller definition, for example:
entity: Entity
controller: EntityController
Then I use this jar in other projects/applications that use the entity.
I want to use the same JAR_A with different persistence unit and different database (in particular, mysql and postgresql) but when I define two persistence unit that include the same class, I have an exception.
So, I comment the other PU and compile the project.
there is a smarter way for use same package with different PU ?
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Nov 19, 2014
I am trying to launch a GUI to my agent-based model (Repast and Eclipse) so that being able to run the model for many times. I am going to produce input parameters based on different distributions for different runs from GUI. Usually we should use batch file for different runs. However, I want to use GUI for this reason because I have GUI that can take care for one run but not for many runs.
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Feb 5, 2014
Can you have multiple key events? by that I mean say you press the right arrow key, or a number on the numeric pad, then you press the letter c. does the second key event get fired? and i can catch both events?
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Feb 10, 2014
For example, if I have a class called Teacher with the constructor:
public Teacher(double yearsTeaching, boolean isMale, double age)
{
this.yearsTeaching = yearsTeaching;
this.isMale = isMale;
this.age = age;
}
How would I add it to these parameters to my ArrayList in my Tester class?
List<Teacher> teachers = new ArrayList<Teacher>();
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May 27, 2014
Here's My code to create multiple JTextfields in a Single Option Pane.
My goal is simple.
Take some input from the user and then store it a TEXT File.
package printer;
import java.awt.Toolkit;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import javax.swing.*;
public class Database {
JTextField name = new JTextField();
JTextField roll = new JTextField();
[code].....
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Sep 13, 2014
Is it possible to have multiple methods in one class?And can I use the Scanner in methods other than the main method?
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Jan 21, 2015
I have this very code:
if (minute > 35 && hosts < 1 && guests < 1)
In this if statement I would also like to add another two possibilities:
first would be: hosts < 1 && guests < 2
second would be: hosts < 2 && guests < 1
Is it possible to somehow add it so it can all be in included in one if statement, and it would look something like that:
if (minute > 35 && hosts < 1 && guests < 1 OR
minute > 35 && hosts < 2 && guests < 1 OR
minute > 35 && hosts < 1 && guests < 2) {}
.. ?
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Mar 27, 2014
I want to return multiple values in my EJB query. The query goes something like this:
SELECT SUM(s.sales) SUM(s.cancels) FROM accounts.
To implement this if I write as below:
Query query = _em.createNamedQuery("Accounts.findAccountData");
Now if I do query.getSingleResult(); how do i retrieve both the values since the ejb finder returns either a single object or a collection?.
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Oct 25, 2014
I have to make a retail item class that has description, price and quantity. I then have to make a CashRegister class that calculates subtotal, tax, total and displays it (toString). I also have to make a driver class to call the methods from main. I have no clue what I am doing and what I have done does not work. I am trying to make it sort of like a cart, in the CashRegister it should ask the user to enter the description, quantity purchased and the price. Then it would send that to the arraylist of retailitem. I am having trouble using those items in my other methods and then do not know how to call those in the driver class.. So here are my classes:
public class RetailItem {
private String description;
private int quantity;
private double price;
public RetailItem(){
description = "";
quantity = 0;
[Code] ....
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Sep 16, 2014
i am currently making a game in java and currently i am working on the basic mechanics. most of it is working fine but i cannot seem to make it so when the user presses and movment key and space to fire a bullet the bullet fires in the direction they are moving. here is the code i have for movement.
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
int bulletx = Player.x + 100;
int bullety = Player.y + 20;
int key = e.getKeyCode();
if( key == e.VK_W){
p.moveUp();
}
if(key == e.VK_S){
p.moveDown();
[code]....
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Apr 25, 2014
I was trying to play around a little bit after learning creating multiple classes and stuff.However,i encountered a strange problem with reading a value from the user and then storing it in a variable.The usual way i do it is
Scanner variableName=new Scanner(System.in);
System.out.println(variableName.nextLine());
But when i trying to print the contents of the variable "variableName" the compiler throws a lot of errors .I am attaching how i have tried that out in my code
import java.util.Scanner;
class laptop{
private String modelNumber;
private boolean hasFan;
private float ramSpeed;
protected int numCores;
//private String input;
[code]....
Without the setInfo() in the laptop class the program functions as desired but i intend to ask the user if he wants to modify something and then reflect the same.
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Mar 12, 2014
how to insert multiple rows in a database..i want to insert multiple rows but this can happen when i hit the submit button once. i use j2ee and db is postgresql.
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May 28, 2014
This program allows the user to select one of each different type of skateboard/accessories items. Then it allows the user to select as many misc items as he or she chooses. The program works fine for the single choices, but I cannot solve the latter part. I have a get method in the misc class that is trying to pull out any selection or selections that were made by the user, but it simply does nothing...
Here's my program, I have four panel classes for each skateboard type, and then I have one class that takes care of adding each panel to the content pane, and calculating the total cost of the item.
Decks Panel Class:
import java.awt.event.*;
import javax.swing.*;
// The DecksPanel class allows the user to selects a specific type of skateboard
public class DecksPanel extends JPanel
[Code]....
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Mar 1, 2015
I have recently start learning about objects and classes in java. I understand that in order to use multiple classes in one file you need one class to be public and the rest are private. But after that I don't understand how to invoke the private class in the public class. I thought if I tried programming on my own I can have a better understanding of it, but had no success.
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