EJB / EE :: Caching Objects - Get Data From Database
Apr 29, 2014How do we cache objects in EJB 2.
My requirement is i need to get data from the database for the first time and retain in cache it throughout the application life.
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Swing/AWT/SWT :: Caching TableModelListener Data For Updates
May 6, 2014how a JTable and respective DB table would be updated via directly editing a JTable: After table cell is updated, the setValueAt method of my custom TableModel is called to change the value of the data vector (assume I'm using vectors to store data). setValueAt then calls fireTableCellUpdated which updates the table view, and calls my custom TableModelListener.tableChanged method. Here is where I would write code to update the database.
This means an Update statement is fired each time a cell changes. Sometimes I would like to only send the Update after the entire record has been updated (and a user clicks a Save button).
Copying Data Objects To Serializable Objects
Jul 27, 2014I am currently working on a project where I need to return data from a database over RMI to a client who requests it. Some of the fields in the Data Object can not be seen by the client so I need to create another object to send over the network instead. The method I use is this...
public static SerializableObject createSerializableObjectFromDataObject(DataObject dataObject){
SerializableObject serializableObject = new SerializableObject();
serializableObject.setField(dataObject.getField());
serializableObject.setAnotherField(dataObject.getAnotherField());
return serializableObject;
}
Is there a better way of doing this? I am creating many subclasses DataObject which all require this static method to be implemented and I can't push it into the superclass because each one needs custom behaviour.
JSF :: Creating Primefaces 4.0 Charts From Database Objects
Jul 27, 2014I'm trying to create a simple bar chart from integer values (measuring number of bulldozers) stored in a mySql DB, in the following schema:
Integer rigId PK;
Integer rigQty;
Date recordDate;
String country FK;
I want to plot the date on the x-axis and quantity on y-axis. I can't seem to find any examples of how to render charts from a database. I just find the generic Primefaces 4.0 examples which uses static data like this:
private void createCategoryModel() { // category chart
categoryModel = new CartesianChartModel();
ChartSeries boys = new ChartSeries();
boys.setLabel("Boys");
[Code] ....
I'm really not sure how to adapt the above to a database method nor have any web searches produced useful examples. I tried something like this, but how to find examples or the type of methods I need to use to create a bar graph from Db values:
@ManagedBean(name = "chartb")
@SessionScoped
public class BarChartBean {
private final Map<Integer, Map<String, Number>> rigNums = new HashMap<>();
// private final Map<Integer, Map<String, Number>> HorasOrcadasPorFunci = new HashMap<>();
private CartesianChartModel cartesianChartModel;
[Code] ....
Objects And Links - Import Database To Java Pane
Nov 23, 2014I would like to import database to the Java pane and connect objects to each other and want to display their information as visually. How can i do.
View Replies View RelatedString Hashcode Caching
Jul 17, 2014Winston Gutkowski in one of the threads that one of the advatanges of String being immutable is that its hashcode could be cached. How does this work? I read somewhere that each String's hashcode is stored in a private int variable, but I don't understand how it is reused.
View Replies View RelatedCaching Downloaded Classes On Client Machine
Sep 30, 2014Does the following code, which gets a class from a remote server, caches the class on the client machine?
URL u = new URL("http://1.2.3.4:80/JavaClasses/MainClass.class");
InputStream input = u.openStream();
DataInputStream data = new DataInputStream(input);
byte classBytes[] = downloadByteCodesFromURL(data);
Class c = defineClass("MainClass", classBytes, 0, classBytes.length);
[Code] .....
Getting Objects Data In Class
Mar 7, 2015I have a class which connects with database and fills object with data. Method looks like this:
//in database class
void getData(anObject a, int id){
//connects with database
a.field1=get...
a.field2=get...
....
//disconnects
}
Now I want to use this method in anObject class, but I can't call it because I don't have created object jet. Is there any way to call this method?
How To Access Objects Data From Another Class
Oct 3, 2014I've been unable to figure out how to access an objects data from another class. I ended up missing a lesson in java and haven't been able to catch up on this topic on my own through my textbook.
Error: has private access
Code:
public class TestCoffeeDrinker {
public static void main(String[] args) {
Coffee latte = new Coffee("Starbucks Tall Latte", 2.85);
Coffee mocha = new Coffee("Starbucks Grande Mocha", 3.95);
Coffee mcdonalds = new Coffee("McDonalds McCafe", 0.99);
System.out.println(mcdonalds.toString());
[Code]...
How To Access Data In Array Of Objects
Apr 23, 2014I want to keep count of how many students are in my array. the array i made up of objects from other classes. like the class Student how do i do this. i have tried contains but better way it to to a loop to go through the array and determine if each object is a particular type but i don't know how to do this. here is the code
import java.util.*;
import java.util.ArrayList;
public class Driver {
public static void main(String[] args){
/* Comments required
PersonFileReader pfr = new PersonFileReader("person.dat");
ArrayList<Person> testData = pfr.readData();
Database db = new Database(testData);
[Code] .....
Java Caching System - Set Expire Time For Object Using Predefined Method
Jul 22, 2014When we are caching an object, how to set expire time for that object by using pre defined methods?
View Replies View RelatedWhy Data Is Not Inserted Into Database
Dec 13, 2014import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
[Code] .....
Data From Database Is Not Showing On Combobox
Sep 17, 2014Whats wrong with my code? The data from my database is not showing on my combo box.. I am trying to get my data in my database to my combo box ..
Here is my Code :
private void Fillcombo(){
Connection con = null;
String url = "jdbc:mysql://localhost:3306/";
String db = "purchasedb";
String driver = "com.mysql.jdbc.Driver";
String user = "root";
[Code] ....
Servlets :: Insert Data To The Database?
Apr 4, 2014i am stucked with a little error in servlets
this is my jsp page
form.jsp
<form action="InsertData" method="post" >
username:<input type="text" name="username">
Password :<input type="password" name="password">
[Code]....
i am getting wroor page not foung 404
Servlets :: Data Is Not Getting Inserted Into Database
Mar 26, 2015I am trying to insert data using servlet but it is not getting into database.
I have a two JSP's form from which i enter the data and using servelt trying to insert the data into database.
JSP page code:
1.add_question_list.jsp
<script language="JavaScript">
function validate(form) {
if (form.question.value == "") {
[code]...
Runnable Jar Does Not Show Data From Database
Mar 13, 2014I am still working on my java course and now we have to create a jar file from a previous project (this is a project where a connection to the database is made and data is shown in a frame).
When I follow the instruction in my course material I don't get it to work. I've tried the following:
1. Open eclipse on windows xp
2. Right click on the project folder in eclipse
3. Click on "export" in the menu that appears
4. Choose "runnable jar"
5. click next
6. I insert the following parameters:
- Launch configuration --> I select my main class
- export destination --> I select the folder D:
- library handling --> Package required libraries into generated jar
7. click Finish
This is what happens when I dbl click the jarfile (wampserver is running):
1. I get an error: "SQL ERROR: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server."
2. I click ok on the message and the following message appears: "SQL Error: null"
3. I click ok on this message and the frame with the fields appears without data from the database.
This is a crosspost to: [URL] ...
Servlets :: Insert Data To Database?
Aug 2, 2014How can we insert data through java servlet?
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.
This is my servlet code:
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String email = request.getParameter("email");
String password = request.getParameter("password");
List<String> errList = new ArrayList<String>();
[code]....
Transferring Data To MySQL Database
Jul 27, 2014try {
is = new FileInputStream(file);
data = new byte[(int) file.length()];
is.read(data);
String extension = "";
int i = file.getName().lastIndexOf('.');
if(i>0)
[Code] ....
Everything works except transferring the image file.
Data From Database Not Showing On Combobox
Sep 17, 2014Whats wrong with my code? the data from my database is not showing on my combo box.. I am trying to get my data in my database to my combo box ..
Here is my Code :
private void Fillcombo(){
Connection con = null;
String url = "jdbc:mysql://localhost:3306/";
String db = "purchasedb";
String driver = "com.mysql.jdbc.Driver";
String user = "root";
String pass= "ajleal";
[Code] .....
Insert Data Into Access Database
Mar 29, 2014I need my java program to insert data into my access database. I get no errors in my code, but it never inserts, deletes the data in my database. Here is my code:
import java.awt.*;
import java.awt.event.*;
import java.sql.*;
public class INS extends Frame implements ActionListener{
Frame f;
Label l1, l2;
TextField t1, t2;
Button b1, b2, b3, b4, b5;
Connection c;
[Code] ....
How To Insert Data Into Database If Not Exists
Oct 10, 2014I have tried this code to insert into datbase if not exists but i get an Exception in thread "main" com.mysql.jdbc. exceptions.jdbc4. MySQL SyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE NOT EXISTS (SELECT teamName FROM Teams WHERE teamName = teamName) LIMIT 1' at line 1
stmt.executeUpdate("INSERT INTO Teams(teamId,teamName,league) VALUES ("+i+",'"+loser+"','"+league2+"')WHERE NOT EXISTS (SELECT teamId,teamName,league FROM Teams WHERE teamName = teamName) LIMIT 1;");
JSF :: How To Read / Insert Data Into Database
May 2, 2014I need getting detailed examples about how I can read/insert into database using JSF code for its different components. I am a beginner in JSF and I have the basics, however, I need the best source which it has useful, easy and detailed steps to understand the techniques for connecting to the DB and how to insert or read data from the database.
I tried to search, but I found the lessons are not useful or not described in details.
Code Not Saving Data To Database
Nov 2, 2014I have a simple project to save data to the database. I have successfully mapped the java class with the database table. The code displays no error, it runs very well but it does not save to database, instead it catches an exception and prints out "saving failed". The database is a mysql database.
This is the managed bean code. Save.java(name=bean)
//imports
@ManagedBean(name="bean")
@RequestScoped
public class Save {
private String username,password,msg;
Session session = null;
Transaction transaction = null;
//GETTERS AND SETTERS
public Save() {
[Code] ....
This is a screenshot of my Hibernate configuration file : hb.jpg
Comparing Data Across Different Database Programmatically?
Oct 22, 2014I am looking to reconcile data between SQL server and Oracle DB post the migration, I need to verify the data (rows/columns) for last 10 years, Before i start writing a Java Utility to accomplish this, My question is are there any existing libraries or API which can accomplish the same ....
View Replies View RelatedCode Storing Input Data In All Three Of Product Objects?
May 7, 2014My problem is that in my program, I have the user input data for one of three product objects, however when I read the data for all three objects, the same data is stored in all of them.
Anyway this is the method from the Interface class:
private void readInput() // the only method in the program that accepts product data from the user {
Store matesStore = new Store();
String name;
int demandRate, productChoice;
double setupCost, unitCost, inventoryCost, sellingPrice;
Scanner console = new Scanner(System.in);
[Code] ....
And here is the method from the Store class:
public static void addData(int option, String newName, int newDemand, double newSetup, double newUnit, double newInventory, double newPrice)
//sets the product data for a particular product {
if (option==1) setData(product1, newName, newDemand, newSetup, newUnit, newInventory, newPrice);
else if (option==2) setData(product2, newName, newDemand, newSetup, newUnit, newInventory, newPrice);
else /*(option==3)*/ setData(product3, newName, newDemand, newSetup, newUnit, newInventory, newPrice);
[Code] ....
The problem I had was with static variables and methods.
Understanding Classes And Objects In Terms Of Data Types
May 8, 2015I have seen many ways of describing what objects are, one being that objects are a user-defined datatype. However, if objects are datatypes, then what does that make classes? To me, it seems as though classes should be the "types" of data defined by the programmer, and objects should be the specific "values" of that user defined data type. As an example, an integer would be a class, while 1 would be a "value" of that class, i.e. an object. From this point of view, I don't see why a specific number would be a data type... Therefore, why do we say that objects are user defined data types rather than classes?
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