I've spent almost 3 hours on googling about java beans and where it is usable. What I've figured out is that a bean has a public non-arg constructor, properties and getters/setters to manipulate them. I also know that a bean contains no logic, only fields. However, I don't fully understand why I need to use beans instead of normal classes even if a class can do the same things like a bean? Are beans used to store data or what?
View RepliesI need to store the data of a bunch of objects of a particular class in files in a predefined directory. Later, I want to get all the files from the directory and turn them into the objects again. Ideally, I'd like to have one file per object and have the files be human-readable and editable without too much difficulty. The class used by the objects will likely be subject to change in the future, as well. To keep things simple, all the data members are either primitives, Strings, or arrays of them. What is the best library/API to use to deal with this situation? Or should I write my own classes for these operations?
I read into serialization, but I read that it doesn't deal well with classes that are frequently modified. I also found articles on Preferences, but none of the ones I saw seem to explain how to best handle reading and writing to and from multiple objects, especially when I don't know a prior all the objects that were written to disk.
I've sample code of jsp and servlets. Below is my code.
Index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<form action="AnnotationServlet">
[code]....
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 have created this project and want to be able to add new members to my members arraylist, store the input in a .txt file and load the new members after closing and opening the program.
[URL] .....
I am working on my second javafx program and I am getting confused. The program that I am writing is a payroll calculator. A secondary window opens at the start of the program where the user first enters the number of employees and clicks submit to save the number and to close this window. Then, the user begins to enters the employee information (first name, last name, pay rate and hours worked) when the user clicks the NextEmp button, I want the data in the text fields to be entered into arrays for later use, then clear the fields for the next use. I am running into 2 issues. The first is the close event for the secondary window that pops up. I cannot figure out the syntax. The second issue that I am running into is the loop to store the data into the arrays. I believe I am getting the text field data correctly, but I cannot figure out how to stop the loop until the NextEmp button is pressed again.
import javafx.application.Application;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.input.KeyCode;
[Code] .....
I have declared an array list that will store data type of 1 Character and 2 integer. The data that will be store in this list is
1. A = {0 3}
2. B = {0 5}
3. C = {0 3}
4. D = {0 3}
5. E = {0 5}
6. F = {0 6}
Now here the alphabets are routers and integers are there con1 and con2 respectively. I have a set of router={ A,B,C,D,E,F}.
Step 1:I have to subtract con1 from con2 i.e. (3-0) of all the routers and
Step 2: then put the router having largest value in new set 1 and
Step 3: then this router will be subtract from the router set.
Step 4:then again I have to repeat the step 1 until the value of routers become <= 1.
Now what I did is I defined 3 arrays first is String array that stores names of routers, 2nd array that stores the first value and 3rd array that stores the second value. I can find the largest value but how to store the name of router against the largest value in the set.
My assignment was to create a class and then write a program that uses the methods of the class I created. All the output is correct except for the Question # Missed. It prints [I@1dd0fe7. The wrong question numbers have to be stored into an array and that array printed. I've tried using a for loop to print, rearranging the code, setting the code to how I did in the other methods. I either get this [I@1dd0fe7 -or- a bunch of 0's. I'm not sure if I am calling the method incorrectly, or just do not have the correct set-up to print the array, or if I am just not grabbing the ones that are incorrect.
public class DriverExam {
// Fields
private boolean result;
private int testTotal;
private int numWrong;
private int [] numMissed;
private char [] answerKey;
[Code] ....
What is the usage of garbage collector in java.
View Replies View RelatedI have created this project and want to be able to add new members to my members arraylist, store the input in a .txt file and load the new members after closing and opening the program.
[URL] ....
My 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.
I am working on a java bean, on a stopwatch
private String displayFormat = "%02d:%02d:%02d";// produces 00:00:00 hour:min:seconds
public void timerHasChanged() {
currentTime = System.currentTimeMillis();
// How long has been taken so far?
long secsTaken = (currentTime - startTime) / 1000;
long minsTaken = secsTaken / 60;
secsTaken %= 60;
long hoursTaken = minsTaken/60;
minsTaken %= 60;
Formatter fmt = new Formatter();
fmt.format(displayFormat, hoursTaken, minsTaken, secsTaken);
timerJbl.setText(fmt.toString());
How would i code the get and set method for format, so in property tab a user can choose if they want the timer shown in seconds, or minutes or hours or seconds&minutes
I am building an app, where I have to store the data eg: "hello ! how are you" in java as a string and then use scanner to get input and check if the entered word is present in the line stored. If it is stored then the entire sentence must be displayed. eg : if the stored string is "hello how are you"
if the entered string is "how", then the entire sentence "hello how are you" should be displayed.
Can I store multiple rows of a table in a two dimensional string array in java.. The table has 3 columns and approximately 10,000 rows.. Some pointers for coding to achieve this...
View Replies View RelatedI am developing an web application with servlets and jsp. I have an issue to store images. I am storing images in folder and their relative path's in mysql database.
When I retrieve path from database then using <IMG> tag i have displayed image like:
out.println("<td><img src="+user.getPlaceImage()+" width='70' height='50' /></td>");
It is working fine with internet explorer but not working (that is Not displaying image) in chrome/mozilla.
How to display that image in all browsers....
This is a general question about best practices for handling persisted data in JSF. My JSF page is going to have several fields that map to a managed bean. Upon a button click the fields of this bean are going to be persisted in a database. Is it better to use another bean with application scope to handle the JDBC code, or should I have a method in the bean itself to handle that? Similarly I'll need a method to retrieve the information upon a user request.
View Replies View RelatedI'm trying to understand the concurrent model of each EJB session bean types.
The singleton is well documented and seems clear to me... Only one instance and many threads using it but each method by default is synchronized because @Lock is defaulted to WRITE. We can let multiple threads use on method with @Lock(READ).
The stateless beans are in a pool I think I read somewhere that the container will ensure only one thread is using one instance at a time but this instances are recycled/reused so many threads can use the same instance but one at a time.
Is this correct ? or is it possible that multi-threading occur in one instance of SLSB ?If in the client I obtain a single reference of a SLSB and share this "instance reference" in multiple threads is it true that all the threads could use different instances on the server side ?
The stateful instance I obtain in the client is linked to one server instance and any method call will target the same instace. If many threads are using the same reference, all method calls will be synchronized and waiting for a certain amount of time that can be defined in @AccessTimeout and if the timeout is reach will end with a ConcurrentAccessException.
Can we use @Lock(READ) and let many thread use the same method like in a singleton ?
I have a primefaces editable datatable with column filtering feature.The datatable has live scrolling feature.The problem that i am facing here is that both filtering and scrolling are happening correctly with Request scoped managed bean but when the scope of the same bean is changed to view scope(javax.faces.bean.ViewScoped) then the filtering happens but on removing the keyed in key word from filter box the table content is not reset to original state and also i am not able to scroll down to next set of records on reaching the end of scrolling.Cell editing feature is working perfectly.
One thing that i observed is ,currently i am querying 5000 odd records to load into datatable.But if the number of records is limited below 5000 scrolling is happening correctly but problem with filtering remains same.I even tested by upgrading to Primefaces 5.1 from 3.Code snippet of xhtml page
<h:form id="form">
<div id="content">
<p:dataTable id="workSpaceList" var="data"
value="#{workSpaceBean.list}" widgetVar="multiSelection"
selection="#{workSpaceBean.selectedRows}" resizableColumns="true"
liveScroll="true" scrollRows="10" scrollWidth="90%"
scrollHeight="70%" styleClass="datatable"
tableStyle="table-layout:auto;width:auto important!;height:auto important!;padding-left:15px;"
scrollable="true" editable="true" editMode="cell"
filteredValue="#{workSpaceBean.filteredWorkSpaceItems}"
rowKey="#{data.lpID}" >
[code]....
I want to get current Computer CPU usage of my computer and display it in Console View of Eclipse? How can I achieve this?
My template code is:
Java Code: public class GetCPUUsage{
public static void main(String[] args){
System.out.println("CPU USAGE IS: ??????");
}
} mh_sh_highlight_all('java');
I added ??? as placeholder for CPU usage because I do not know how to retrieve RAM usage by Java.
I'm wondering if there's a way to build a template for managed beans which could be extended by a constructor instead of re-writing beans for each entity. I can do that quite easily for Dao objects by creating facades and using those facades to create Dao implementations for specific entities. Not sure if the same concept works for managed beans and haven't really come accross any searches.
I wrote the following but I'm not sure how to implement or even if the concept of generics and templating can be applied to managed beans in the same way it can be applied to Dao classes:
public class BeanTemplate<T> {
private ListDataModel<T> listModel;
@EJB
private GenDao dao;
private Class<T> entityClass;
[Code] .....
The above assumes there's only one method needed in the bean. I thought of extending like this:
public class EmployeeBean extends BeanTemplate<Employee> {
public EmployeeBean() {
super(Employee.class);
}
// how can the methods be called??
Is the same concept for creating dao templates possible for managed beans?
My code of start.xhtml is:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en"
xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://xmlns.jcp.org/jsf/html"
xmlns:f="http://xmlns.jcp.org/jsf/core">
[Code] .....
when I deploy the app(glassfish) I get this message only:
hi #{user.minimum} a #{user.maximum} .
Instead of a picture: wave.med.gif and message:
hi 0 a 10 .
file hierarchy is attached
If I have the next request scoped JSF bean for example:
public class UserBean {
private String name;
private String surname;
public String saveUser(){
//service is called to save a user
}
public String updateUser(){
//service is called to update a user
[Code] ....
1.In struts for example the Action classes are singletons and I think is the way it has to be because they contain business logic and is the same logic for every user but in JSF because of you mix properties from a form and methods with business logic, these beans have to be request scoped like the above one but is very wierd that a bean which contains business logic(saveUser()....) be request scoped;I dont see it effective, is like creating a new servlet each time you want to save a user but I think is the way JSF works, right?
2 To avoid the mixing of form properties in a bean with business logic, some people say to have the form beans request scoped and actions beans session scoped.
- Is this right?
- How then can you get the request form bean in the action bean?
- The scopes in JSF are request, session and view so you cannot create singleton action beans, the best you can get is a session action bean, right?. Once again I dont see the point of creating action beans with session scoped,they should be application scoped if it existed
I have a class as shown below. This class has a method addFilter with 2 parameters (type String and type Command1 )
public class Command1 {
public StringBuffer addFilter(String query, Command1 dataBase) {
//concrete implementation
return query;
}
}
I have another class Command2. Here I need a similar method. The only difference is in the type of parameters passed. (type String and type Command).
public class Command2 {
//TO DO:
public StringBuffer addFilter(String query, Command2 cmd) {
//concrete implementation
return query;
}
}
I have started by using Interface
public interface Helper {
public StringBuffer addFilter(String query, XXXXX parameter2);
}
I would like the classes Command1 and Command2 to implement the interface Helper and override it these two public classes.
However my problem is in dealing with the 2nd parameter. Am I right in my approach? How do I handle this issue?
What are the best practices for unit testing MDBs and session beans ?How can they be tested without running an application server ?
View Replies View RelatedI created an instant messenger using java. When I have the Server that communicates between the clients and one client running on my Computer the CPU Usage is at 100%. It really slows down everything else I'm doing and I figure this might be an issue if I gave this to people to use. I don't want the client taking up a lot of CPU Usage if they're just running it in the background while doing other things on their computer. The program utilizes multithreading. Each thread is constantly being polled for input.
The Server, as seen below, has two threads. I explain what the threads do before the code. There is also another while loop running constantly in the server that is waiting for sockets to connect. The loop does not run constantly at the line socket.accept(); it stops and just waits.
The User, split into a menu and chat window, has two threads as well. I explain what the threads do before the code. After I originally posted I put a 100 ms sleep in all my threads. CPU Usage is still at 100%*
This thread listens for input from the user. The input tells the server what action to take. There is a thread running for every user currently connected to the server.
public void run()
{
try
{
input = new DataInputStream(user.getSocket().getInputStream());
output = new DataOutputStream(user.getSocket().getOutputStream());
[code]....
I would like to limit my bandwidth usage when accessing/downloading files (similar to the --limit-rate 50K option for curl and wget) as the website has limited bandwidth. I am not exactly sure how to implement this, but I'm guessing it be accomplished via the BufferedReader? I have attached the current code below.
import java.io.OutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
[Code]....
I have seen in some examples like URL... a good design is to have the model and the action methods in one just single bean and the model not to be a separated class but a few properties like this:
public class CustomerBean implements Serializable{
//DI via Spring
CustomerBo customerBo;
[b]public String name;[/b]
[b]public String address;[/b]
//getter and setter methods
[code]...
Some questions:
1. If you are using hibernate or any other ORM like the above example(URL...), why not to use the hibernate pojo bean directly like it represented the form instead of using properties?:
public class CustomerBean implements Serializable{
//DI via Spring
CustomerBo customerBo;
[b]Customer customer;[/b] //represents the properties of a form
//getter and setter methods
public void setCustomerBo(CustomerBo customerBo) {
this.custom
2. Why is it said that JSF represents the purest MVC? Spring separates the model from the view too and Struts does too. I dont really understand it