Servlets :: How To Persist Data Without HttpSession
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
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?
I would like to understand how does multipart/form-data works during file upload scenario's, Does it chunks the data from client to server while transferring the files ?
I am able to upload the file to the server, but I am not able to get the value of text1 in the servlet (I am getting null value of text1 in the servlet), I need this textfield in the form to submit some additional information while uploading it to the server.
--> Is enctype="multipart/form-data" option of form doesn't allow other form data to be submited? if it doesn't allow it then what are the other options I have to send this additional textfield to the server.
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
I'm using EclipseLink, WildFly, EJB, postgresSQL and JSF.I'm trying to persist some countries and their localities.So I've:
- Two entities Countries and Localities in which I specify respective columns and relations. - Abstract Session beans for entity classes: AbstractFacade providing basic crud methods and entity manager. - Two concrete session bean for entity classes: CountriesFacade and LocalitiesFacade. - A JSF managed bean named geoJSF. - A JSF page with a form allowing to insert new country and localities.
In geoJSF I'm injecting via EJB CountriesFacade as property named cf and LocalitiesFacade as property named lf.For the actual inserting country and locality I'm using geoJSF.country and geoJSF.locality. When the form is submitted I'm simply doing:
this.cf.create(this.country); this.locality.setCountry(this.country); //<- this throw an exception (unique constraint violation) due to the attempt to reinsert this.country this.lf.create(this.locality);
I disabled all cascade among relations definitions.Based on what I know this.country should appear detached to entity manager so, setting relation the entity manager try to re-persist it.
i get this error when trying to Persist a customer Entity in my web application using netbeans with the default glassfish server persistence provider eclipselink(JPA2.0)
error is
SEVERE: javax.validation.ConstraintViolationException: Bean Validation constraint(s) violated while executing Automatic Bean Validation on callback event:'prePersist'. Please refer to embedded ConstraintViolations for details.
the table that i want to write to has the following colums id ==> primarykey auto increment not null int name == varchar(45) not null phone ==> varchar(19) nationalIdNo ==>varchar(19) balance ==> bigdecimal(6,2) not null default(0.00)
in my addNewCustomer i only need to set name, phone and nationalIdNo only this is my code
/* * To change this template, choose Tools | Templates * and open the template in the editor. */ package session;
I am making a quiz app and stuck with this problem. User is presented with question with options he select one radio button and move on to next question by clicking next button.
Now when user clicks on the previous button to change the previous selction , I want his previous selection to be shown selected. How can I do that.
I have a ComboBox I'm using for a cellEditor. The list of items in the comboBox might have colors behind them, which I've managed to render. What I haven't figured out is a good way to keep the color in the cell after the item is selected.I don't' want to have a persistent comboBox in the cell, i only want to see it when editing that cell.
public TableCellEditor getCellEditor(int row, int col) { if (row==theRow && col==theCol) { JComboBox<?> combo = new JComboBox<Object>(getPickListEntries()); combo.setRenderer(new PickListRenderer(combo)); combo.setBorder(BorderFactory.createEmptyBorder()); }
I have an html form with 200 input fields of type text. The first input field contains the name of a book author and the remaining 199 fields hold each a title of a book that he or she has written. I also have a servlet that processes the form data and sends it to a file. The entered data is restricted to a combination of the characters "a...z A...Z". how do i go about with creating my html page. The input fields are just too many, how to retrieve the 200 values in servlet.
<html> <head> <script> var k; function testField(Expression){ k=1; var str1="abcdefghijklmnopqrstuvwxyz "; var sor=Expression;
I can insert data to table by using JSP Scriptlet easily but I have a hard time with servlet.
public class UsertToDatabase() { public boolean inserUser(String name, String email, String pwd) throws SQLException { PreparedStatement pstmt = null; boolean flag = false; System.out.println("start"); openConn(); System.out.println("start_1"); if(conn == null) {
[code]....
I am positive that the above code function fine. The problem is whenever I call UserToDB() class inside the servlet, and I got this error: java.lang.ClassNotFoundException: org.postgresql.
Driver which mean that my conn (connection) is not connected to the database but I have ensure to do so by calling openConn() before start the transaction.
Now I want to store those username and age(in .html) somewhere and I want those information in welcome.jsp. Now, I'm storing all those in session itself(In doGet method(servlet)).
2 Doubt) Also, when I get the session in servlet HttpSession session = request.getSession(); line No. 27. The session value is org. apache. catalina. session. StandardSessionFacade@69a8bf4f...I'm expecting that session is to be empty. Because, I dint store anything until that line.
I'm new to json and the web. My purpose is to use json data from a server and parse it and show meaningful data to the user. I am aware of json parsing, so no sweat there. However, I would like to know how json data is sent to the front end after which it can be parsed.
Usually in my json parsing examples, I have a variable like var data = ]OR I do a getJSON on a data.json file which I have stored in the project folder. However, I want this data to come real time from a servlet. How to go about this?
So, basically my question is, how do I send real time json data from a servlet backend, say some records which I have extracted from the database using jdbc?
What is better and easier approach for exchanging data (in my case list of objects) between servlets in different nodes in same cluster? I thought about RMI or just direct url servlet call. But it seems that I'm missing something here.
My problem is the following:
I have to create some kind of diagnostic storage for each cluster member. It will collect all information and errors during application work.
And If I need to check application status I do web request and it will show me that these servers (cluster members) are okay and that node has an issue.
I have a very simple HTML form with a textField for a name, and add button to add the name to a MySQL database, and a sort button to sort the names in the database and display them. I almost have it working, however when I hit the "sort" button; I get the message that appears after a user clicks the add button along with the sorted list of names. It looks like this:
Please go back and add a name or sort. Bill Jones David G Debbie Downer Jane Doe Joe Smith John Doe Mike Jones Paul Smith Susan Jones
What I have to change on my code to make just the list show up by itself when the user clicks sort?
Is it possible to get the list/ values in html/jsp from servlet?
I have a table inside an html/jsp page and when the user clicks a button I need to refresh the whole page with some additional text message.
Currently what I am doing is that I am using a java bean for the jsp page that contains a list of values inside the table then store it in session but I think there is a better way without storing it in session.
I tried using request.getParameter() but it only returns string.
i am newbie to servlet and m working on a project like online shopping. I have list of data items in my database and i am able to fetch and display the data from database but i want to know that how can i store these data items in ServletContext so that i can use use it frequently in other pages.
In one jsp page, I submit a form with a message body with following html code (which is store in "MsgBody" in my request)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
[code]....
But when I submit my form, I received in my servlet a parameter "MsgBody" without several tag like <html>/<body> ... do you know this behavior, by default tag are delete ?
I need to get the html in string when i hit the hit the jsp in servlets basically i need to put the output of jsp in pdf file when i hit one link i need to download that data in pdf file. I am using itextpdf.
//Get the output stream for writing PDF object OutputStream outStream=pResponse.getOutputStream(); ByteArrayOutputStream baosPDF = new ByteArrayOutputStream();
[Code] ....
I need to convert the sample download.jsp to html so that i can parse
