Servlets :: Determine Which HttpSession Attribute Value Changed?
Feb 15, 2015
I'm looking to figure out if it's possible to do the following:
HttpSession session = request.getSession();
session.setAttribute('name', 'Jane_Doe');
// more code here
session.setAttribute('name', 'John_Doe');
Obviously, you can use the HttpSessionAttributeListener to determine which attribute has changed. However, it doesn't return the new value but rather the old one.
You can use the HttpSessionEvent listener to determine when a session object has been changed.
Is there a way you can determine when a session object changes (and it does NOT occur when the setAttribute method is called...) and determine the updated key:value pair?
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Jul 3, 2014
I have a basic HTML calculator that asks the user to input 2 integers and select from a dropdown their desired math operation:
The servlet will process the calculation and counts how many times a certain operation has been used:
The counter for Multiplication has incremented accordingly.
HTML:
<form action = "processcalc.html" method = "post">
<table>
<tr>
<td>First Operand:</td>
<td><input type = "text" name = "firstOperand" required></td>
[Code] ....
Question: However, when I press "Go Back" and process a new computation, all counters reset to 0. Is there a way without using HttpSession to persist the counter values? (It has not been taught to us, so we are not allowed to use it yet.)
For example, going back and having below input...
First Operand: 4
Operator: +
Second Operand: 5
...will result to...
Addition: 1
Subtraction: 0
Multiplication: 1 (counter from previous computation maintained)
Division: 0
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Jan 9, 2015
I am learning few concepts in servlets. And i came across this doubt. We used to send data over network using httpsession as below.
HttpSession session = request.getSession();
Object obj = new Object();
session.setAttribute("object", obj);
And get the data in JSP with below code
<%= session.getAttribute("object")%>
However I am not sure whether HTTPSession is serializable or not.
How HTTPSession works?
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Jan 11, 2015
I am getting following exception.
Jan 11, 2015 10:08:23 PM org.apache.catalina.session.StandardSession writeObject
WARNING: Cannot serialize session attribute cart for session 2F9FF7A5ABC3620BD5B3BC0C4D46C558
java.io.NotSerializableException: org.apache.tomcat.jdbc.pool.DisposableConnectionFacade
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)
[Code] .....
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Dec 29, 2014
Being new to java I am a bit lost as to why my session attribute for this banking app wont add the deposits to the session var... it just keeps going back to the amount I set it to originally - so if I set the beginning balance to 3000 then deposit 100 it becomes 3100, but if I then try deposit another amount eg. a extra 200 it becomes 3200 not 3300 like it should be !!
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.text.DecimalFormat;
public class SessionBank extends HttpServlet
[Code] .....
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May 21, 2014
i have file index.jsp , that approach to reguar java class and call function . in that function i want to get attribute from session like this :
List<Coupon> couponsList = (List<Coupon>)request.getSession().getAttribute("listOfCouponsThatNotExpired");
because this regular java class i get error message ,how to solve this ?
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Nov 3, 2014
I just want to know how to pass an Attribute along with its value from servlets to a plain Java class. Im using java beans but it's showing null...So as an alternative im using session to access variables in java class..
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Feb 26, 2014
I am generating java script tag and javascript code in servlet and displaying it in each jsp page. i include this in every jsp in my application. I am preparing the following javascript content and diplayin each jsp
<script type="text/javascript"> BOOM.addVar (clientId = SOME universal unique ID ) </script>
the clientid will be uniqueid it gets generated every time.
Here my question is, is there any possibility the clientId will be store in browser cache or third party cache server. if yes how to prevent clientId from cache.
I don't want to prevent the whole jsp file from cache. i just want to prevent only that particular field. so that i can use advantages cache and also prevent particular header field to be cached.
Also can we prevent particular http header attribute from cache.
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Apr 22, 2014
I need to be able to detect IE 9, IE 10, IE 11 and the latest from Firefox and Chrome. The old method using the user-agent string is unreliable and not recommended. There is a different approach called, "Feature Detection". But I need to know what features to test to determine the browser. I can write it myself, or if there is a handy dandy API using feature detection already written that would be OK too.
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Jan 23, 2014
I created tableviewer ( jface ). All the columns are editable ( using EditingSupport )
I want to know when cell is changed and then to raise a flag in other column. meaning that you start to write any data in the cell. I know that I need to create event of key changed listener to the cells. ( or there is different way )
How I can have access to the cell ? where do I need to add the event
public class MyGridViewer extends TableViewer {
public MyGridViewer (Composite parent) {
super(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL | SWT.FULL_SELECTION | SWT.BORDER);
final Table table = this.getTable();
table.setHeaderVisible(true);
table.setLinesVisible(true);
[Code] ....
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Jun 15, 2013
I am wondering where the attributes I put into the Httpsession are stored.
For example, if I do the following
HttpSession session = request.getSession();
session.setAttribute("usr", usr);
session.setAttribute("pwd", pwd);
where does the ("pwd", pwd) pair store?
In my case, my web application needs to use the usr and pwd to login to another application, so I have to store them somewhere. So for security reason, if the pwd is kept in the browser side, I need to encrypt it first before I put it in the session. On the other hand if it is stored in the server memory then encryption seems not necessary
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Sep 1, 2014
In my program I want to 2 images changed randomly regulations, but on frame appear only img4. What is wrong?
public class Yes extends JPanel {
Image img3 = new ImageIcon("Yes/Untitled3.png").getImage();
Image img4 = new ImageIcon("Yes/Untitled4.png").getImage();
Random rand = new Random();
int randomNum = rand.nextInt();
[Code] ....
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Mar 9, 2015
I'm working on Java-GUI implementation in Ubuntu. Used font-type in the application throughout is "Arial". At earlier stage of application it was the same font-type("Arial"). As the implementation grew the font-type has been changed automatically to another font type. It seems Serif-font type.
Now I could not able to figure out the problem; why it is so.
Note- I used HTML code also for setting font style of Dialog box messages and buttons. This is the only point which I figured out. Can it is ?
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Oct 10, 2014
I am having an issue with using FileWriter to print some text to a text file. In the following code, I am supposed to be able to print the initial attributes and the user changed inputs into a file but all I am getting is the memory locations of the objects I created in one long line.
package project3final;
import java.io.*;
import java.util.*;
public class Project3Final {
static class Instrument {
char [] stringNames = {'E', 'A', 'D', 'G', 'B', 'E'};
private final String instrumentName;
[Code] .....
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May 6, 2014
My project in eclipse..I get the error below when I run MyTagUser.jsp -
HTTP Status 500 - /jsp/MyTagUser.jsp(14,0) Attribute subTitle invalid for tag Header according to TLD
org.apache.jasper.JasperException: /jsp/MyTagUser.jsp(14,0) Attribute subTitle
invalid for tag Header according to TLD
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)...et
[code]...
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Mar 13, 2014
How can I store in database an user Session attribute along with other informations provided in the same form?
<p:outputLabel value="user ID:" for="informer" />
<p:inputText id="informer" value="#{session.getAttribute('userID').toString()}"
title="informer" disabled="true" />
I've already tested with disabled="false", too, but only the Session attribute is saved as NULL, though it appears in the form field. The other fields are saved properly.
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Oct 22, 2014
context.getELContext().getELResolver().getType(context.getELContext(), null, "value")
Here "value" is an attribute name. By this we can get data type of the attribute.
By somehow can we set the type also?
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May 13, 2014
I don't know how to read the attribute maxLenth. The way in the image I have done drive me to the error below.!
Piece of XSL:
<?xml version="1.0" encoding="UTF-8"?>
<c:message xmlns:c="ictt"><c:de format="B" lengthField="0" name="BIT MAP, PRIMARY" number="000"/>
<c:de format="B" lengthField="0" maxLength="008" minLength="008" name="BIT MAP, SECONDARY" number="001" subFields="00"/>
Piece of Java Code:
int length = Integer.parseInt(spec.getAttribute("maxLength"));
[5/13/14 14:52:19:497 CDT] 00000028 SystemErr R java.lang.NumberFormatException: For input string: ""
[5/13/14 14:52:19:497 CDT] 00000028 SystemErr R at java.lang.NumberFormatException.forInputString(Num berFormatException.java:63)
[5/13/14 14:52:19:497 CDT] 00000028 SystemErr R at java.lang.Integer.parseInt(Integer.java:502)
[5/13/14 14:52:19:497 CDT] 00000028 SystemErr R at java.lang.Integer.parseInt(Integer.java:531)
maxlenth.jpg
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Feb 3, 2014
Here, I have just tried out to take a value from the database and storing it into local variable then I want to have that value in the value attribute of <input> tag but somehow, I can't get it..
Here, below is my code..
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "[URL]....">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
[Code]...
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Oct 27, 2014
We've implemented the Whitelist and there's an application I need to use the Force attribute with, however, I'm unable to get this to work. As I read it, this code says use Java 1.6_24 for Example.com and any other applications are blocked from running. There are three versions of Java installed - 1.6_24, 1.7_65 & 1.8_25. The Java console shows 1.8_25 being called.
Here's the ruleset.
<ruleset version="1.1+"> <rule> <id location=https://example.com />
<action permission="run" version="1.6_24" force="true" /> </rule>
<rule> <id /> <action permission="block">
<message> This application is blocked due to Java restrictions, please contact the Service Desk for assistance.</message> </action> </rule></ruleset>
I also tried
<action force="true" permission="run" version="1.6.0_24" />
and also
<action force="true" version="1.6.0_24" permission="run" />.
The Java console is still showing version 1.8.0_25.
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Mar 17, 2014
I have the below code with spaces on uri and prefix (directive attribute).
<%@ taglib uri=" news.tld" prefix=" news" %>
how to fix without altering the JSP? Can i handle with web.xml or any other property available.
I have hundreds of jsp like this and wanted to handle without code fixes.
I tried JSP trimSpaces but it fixes the namespace but not the attributes.
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Feb 13, 2014
i have a field that varies from 10 to 3000 VARCHAR in DB. A field called IDTEXT in a database that can be even a single word or up to a max of 3000. I want to display that in a form. Based on its size i want to very the size of the <h:inputTextarea>. How can i do it..will i be able to set row property from bean?
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Dec 29, 2014
why my session attribute for this banking webapp wont add the deposits to the session var... it just keeps going back to the amount I set it to originally - so if I set the beginning balance to 3000 then deposit 100 it becomes 3100, but if I then try deposit another amount eg. a extra 200 it becomes 3200 not 3300 like it should be !!
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.text.DecimalFormat;
[code]....
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Feb 22, 2014
Sample XML:
XML Code:
<Books>
<Book id="1" Name="C#">
<URL>http://localhost/download/M1.xml</URL>
</Book>
<Book id="2" Name="Oracle">
<URL>http://localhost/download/M2.xml</URL>
</Book>
<Book id="3" Name="Archius">
<URL>http://localhost/download/M3.xml</URL>
<URL>http://localhost/download/M4.xml</URL>
</Book>
</Books> mh_sh_highlight_all('xml');
I have to fetch only the book name attribute and use it for display .However say for example ,I have got the list of Books ie(C#,Oracle,Archius) ,passing this value to a method should return me an array of URL nodes value within it.
The idea is to display the book names in a list and then on user selection , corresponding URL needs to be fetched.
Was able to get the loop for traversing the nodes
[java=code]
NodeList nodeList = document.getDocumentElement().getElementsByTagName ("Book");
for (int i = 0; i < nodeList.getLength(); i++) {...
[java=code]
So
a) Display the BookNames
b) Get the corresponding URL's for the particular book if I pass the Bookname
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Feb 23, 2014
In a form i used <h:commandButton> i called a Javascript function. Though the function returns false , form is submitted and action method is called. I used like this
<h:commandButton onclick="test();" action="{#bean.menthod}">
test- javascript method returns boolean value false.
Above doesn't work. Below mentioned code alone worked. I want to know why
<h:commandButton onclick="if(test) return true;else return false" action="{#bean.menthod}">
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Jul 6, 2014
Can be :
results = null;
results = new double[2];
results = new double[50];
results = new double[100];
How determine size of this table : System.out.println("table size=",???);
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