(retain) properties in the singleton class

Hi,
What happens with the properties declared with (retain) in the singleton class:
MyClass *foo;
@property (nonatomic, retain) MyClass *foo;
I am using a singleton class as explained http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CocoaFunda mentals/CocoaObjects/CocoaObjects.html#//apple_ref/doc/uid/TP40002974-CH4-SW32 which should NOT be released.
I see no way to call
[foo release].
My guess is that these properties will be allocated once and persist though entire life of the singelton - which is not a leak.
correct?

leonbrag wrote:
My guess is that these properties will be allocated once and persist though entire life of the singelton - which is not a leak.
correct?
Yes. Of course, there are still ways to get rid of singletons if you really want/had to. In some cases, you could have a singleton that allocated system resources that aren't automatically released when a program ends. There are ways to clean up such things if you run across them. Look at the "applicationWillTerminate:" notification, for example.

Similar Messages

Is the singleton class single in threads?

I have a class designed by singleton pattern.
I use this in many threads in one VM.
I found every thread had a different instance.
Why?
And if I want to share information with different
threads,how can I apply singleton in this context?

I know why!
In my singleton class,I don't add the keyword "synchronized".
Code below:
public static MySingleton getInstance(){
if(instance == null){ //miss the keyword "synchronized"
instance = new MySingleTon();
return instance;
So when threads call this method at the same time,
many instances created.

Do you have to Discovery ALL the Properties defined on a Class before an instance of said class will be created

Hello
I am learning how to create management packs with VSAE and have a question please.
When defining a Class based on LocalApplication (which I believe already has a hosting relationship with Windows Computer and therefore no need to create a hosting relationship?)
let say I define two properties one called Version and the other Vendor both based on registry values, so I include the discovery of these regsitry values in my discovery (along with the regsitry key exists to check the actual app is installed).
Now if I have a Server with only two of the above three registry items created e.g. the actual Key and Version string value but not vendor string value. Will an instance of the Class be discovered and thereby viewable in the 'discovered inventory' view?
Or do ALL properties have to be present (as defined on the class definition) for an instance of said class to be created?
Thank you
AAnotherUser__
AAnotherUser__

Hello Vladimir thanks for taking the time to reply
So if I have three properties definded on my custom class, none of which are key properties and I only discover two of them (as the registry key or what ever is missing for the last property) the class should still be discovered as there are no key properties
for the custom class and therefore no key properties missing from the discovery, is that correct please?
Also I understand I have to Discover any key properties of the classes parent/s
for example
<InstanceSettings>
    <Settings>
      <Setting>
        <Name>$MPElement[Name="Windows!Microsoft.Windows.Computer"]/PrincipalName$</Name>
        <Value>$Target/Property[Type="Windows!Microsoft.Windows.Computer"]/PrincipalName$</Value>
      </Setting>
     <Setting>
        <Name>$MPElement[Name="System!System.Entity"]/DisplayName$</Name>
        <Value>$Target/Property[Type="Windows!Microsoft.Windows.Computer"]/NetbiosComputerName$</Value>
      </Setting>
    </Settings>
I have done this, but my Class is not being discovered.
Then I saw a post which had the following, under the Class Discovery Section (along with the other properties of the class)
<Property TypeID="System!System.Entity" PropertyID="DisplayName"/>
Therefore perhaps I need to add this as a property as well as an InstanceSetting?
I am using SCOM 2007 R2 at the moment
Thanks very much
AAnotherUser__
AAnotherUser__

Best Practice: passing properties to a Singleton

Hi,
I have an object in my app that must only exist once. It is a DatabasConnectionPool. I would like to implement it as a Singleton and access it from anywhere in the app with
DatabaseConnectionPool dbcp = DatabaseConnectionPool.getInstance();
But the thing is that I would like to pass it some settings: number of connections to the database, username and password, ...
If I had a constructor for the class I would pass a Properties object with the constructor containig all the values but how do I do it with a Singleton?
Right now I have:
class Singleton {
private static Properties _appProps = null;
private static Singleton _instance = null;
static public void setProperties(Properties appProps) {
_appProps = appProps;
static public Singleton getInstance() {
if (null == _instance) {
instance = new Singleton(appProps);
private Singleton(Properties props) {
So, the Launch code for the application reads the .properties files and calls:
DatabaseConnectionPool.setProperties(props);
WebServer.setProperties(props);
LDAPServer.setProperties(props);
Thanks a lot for your time guys!
Rafa

You don't need synchronization at all if you do it the way a previous post suggested:
private static Singleton instance = new Singleton();
public Singleton getInstance(){
return instance;
}This is lazy initialization by default because the singleton instance will only be created when the class is loaded into memory. It will be loaded into memory when you first call getInstance() so it's already using lazy initialization.
The properties question seems to have several options
1. Use your setProperties method to pass in dynamic properties. This will potentially make your singleton behave differently between uses if you change its properties while it's running.
2. Hardcode the properties inside the singleton. This doesn't allow dynamic changes.
3. Your connection pool is probably dishing out Connection objects and creating new ones when needed right? So, put the Connection creation in a different class called ConnectionFactory and pass in the factory to the singleton. This way you can customize the kind of connections to make in the factory without changing the singleton code. All the singleton cares about is saying factory.createConnection() and returning it.

To ragnic and other about Singleton class

Hi ragnic. Thanks for your reply. I posted the code wrong. Heres' my correct one.
I have a GUI first loaded information and the information is stored in a databse, I have some EJB classes..and my singleton class ABC has some method to access to the EJB..
so my first GUI will gather info using singleton class and later if I click on
a button in my first GUI class, will pop up another frame of another class , this class also need to class setPassword in my Singleton..
are my followign codes correctly??
iS my Class ABC a SINgleton class? thanks
Is my class ABC use as single correctly. And It is called from other classes is also correct?
I'm new to java and like to learn about Singleton class.
But I really dont' understand it clearly after reading many examples of it.
I have a project to convert my class abc to a singleton.
But I dont know how to do it.
In my class(soon will become a singleton) will have few methods that later I need to use it from another class A and class B.
I have a GUI application that first load my class A..and my class will call
class abc(singleton) to get some information from it.
and then in class A has a button, if I click on that button I will call SIngleton class again to update my password, in the singleton class has method calls updatePassword. But I dont know how to call a singleton from other class.
I have my code for them below:
1)public class ABC //attempt using a singleton
private static ABC theABC = null;
private ABC(){}
public synchronized static ABC getABC()
if(theABC == null)
theABC= new ABC();
return the ABC;
public void updateUserInfo(SimpleUser user)
throws UserNotFoundException, DelegateException
try
UserCollectionHome userCollectionHome = (UserCollectionHome)
EJBHomeFactory.getFactory().lookupHome("vista/UserCollection",
UserCollectionHome.class);
UserHome userHome = (UserHome)
EJBHomeFactory.getFactory().lookupHome("vista/User",UserHome.class);
UserCollection uc = userCollectionHome.create();
uc.updateUserInfo(user, userHome);
} catch(HomeFactoryException hfe) {
hfe.printStackTrace();
throw new DelegateException(hfe);
} catch(RemoteException re) {
re.printStackTrace();
throw new DelegateException(re);
} catch(CreateException ce) {
ce.printStackTrace();
throw new DelegateException(ce);
} catch(FinderException fe) {
fe.printStackTrace();
throw new UserNotFoundException();
public SimpleUser getID(String id)
throws UserNotFoundException, DelegateException
try
UserCollectionHome userCollectionHome = (UserCollectionHome)
EJBHomeFactory.getFactory().lookupHome("vista/UserCollection",
UserCollectionHome.class);
UserHome userHome = (UserHome)
EJBHomeFactory.getFactory().lookupHome("vista/User",UserHome.class);
UserCollection uc = userCollectionHome.create();
SimpleUser su = uc.getID(id, userHome);
return su;
} catch(HomeFactoryException hfe) {
throw new DelegateException(hfe);
} catch(RemoteException re) {
throw new DelegateException(re);
} catch(CreateException ce) {
throw new DelegateException(ce);
} catch(FinderException fe) {
throw new UserNotFoundException();
public void setPassword(String lname,String pw)
throws UserNotFoundException, DelegateException
try
UserCollectionHome userCollectionHome = (UserCollectionHome)
EJBHomeFactory.getFactory().lookupHome("vista/UserCollection",
UserCollectionHome.class);
UserHome userHome = (UserHome)
EJBHomeFactory.getFactory().lookupHome("vista/User",UserHome.class);
UserCollection uc = userCollectionHome.create();
uc.setPassword(lname,pw, userHome);//assume that all lname are differents.
} catch(HomeFactoryException hfe) {
hfe.printStackTrace();
throw new DelegateException(hfe);
} catch(RemoteException re) {
re.printStackTrace();
throw new DelegateException(re);
} catch(CreateException ce) {
ce.printStackTrace();
throw new DelegateException(ce);
} catch(FinderException fe) {
fe.printStackTrace();
throw new UserNotFoundException();
}//Do I have my class as a Singleton correctly???
2)//Here is my First Frame that will call a Singleton to gather user information
public A(Frame owner)
super(owner, "User Personal Information",true);
initScreen();
loadPersonalInfo();
* This method instantiates all the GUI widgets and places them into panels and
* onto the frame.
private void initScreen()
txtFname = new JTextField(20);
txtLname=new JTextField(20);
btnsave =new JButton("Save");
btnChange= new JButton("Click here to change PW");//when you click this button there will be a frame pop up for you to enter informaton..this iwll call class B
JPanel pnlMain=new JPanel();
JPanel pnlFname= new JPanel();
pnlFname.setLayout(new BoxLayout(pnlFname, BoxLayout.X_AXIS));
pnlFname.setBorder(BorderFactory.createEmptyBorder(0,87,0,90));
pnlFname.add(new JLabel("First Name:"));
pnlFname.add(Box.createRigidArea(new Dimension(5,0)));
pnlFname.add(txtFname);
JPanel pnlLname= new JPanel();
pnlLname.setLayout(new BoxLayout(pnlLname, BoxLayout.X_AXIS));
pnlLname.setBorder(BorderFactory.createEmptyBorder(0,87,0,90));
pnlLname.add(new JLabel("Last Name:"));
pnlLname.add(Box.createRigidArea(new Dimension(5,0)));
pnlLname.add(txtLname);
pnlMain.add(pnlFname);
pnlMain.add(pnlLname);
pnlMain.add(btnsave);
pnlMain.add(btnChange");
btnSave = new JButton("Save");
btnSave.setActionCommand("SAVE");
btnSave.addActionListener(this);
btnCancel = new JButton("Cancel");
btnCancel.setActionCommand("CANCEL");
btnCancel.addActionListener(this);
JPanel pnlBottom = new JPanel();
pnlBottom.setLayout(new BoxLayout(pnlBottom, BoxLayout.X_AXIS));
pnlBottom.setBorder(BorderFactory.createEmptyBorder(25,55,0,0));
pnlBottom.add(btnSave);
pnlBottom.add(Box.createRigidArea(new Dimension(25,0)));
pnlBottom.add(btnCancel);
pnlMain.add(pnlBottom);
this.setContentPane( pnlMain);
setSize(500,500);
GraphicUtilities.center(this);
theABC=ABC.getABC();
//Do I call my ABC singleton class correctly??
private void loadPersonalInfo()
String ID= System.getProperty("user.name");
SimpleUser user = null;
try {
user = ABC.getID(ID);
//I tried to use method in ABC singleton class. IS this correctly call?
} catch(UserNotFoundException nfe)
JOptionPane.showMessageDialog(new JDialog(),"You have not yet registered.",
"User Not Found",JOptionPane.WARNING_MESSAGE);
System.exit(0);
} catch(DelegateException de) {
JOptionPane.showMessageDialog(new JDialog(),"You have not yet registered",JOptionPane.ERROR_MESSAGE);
System.exit(0);
currentUser = user;
txtFname.setText(currentUser.getFirstName());
txtLname.setText(currentUser.getLastName());
//This information will be display in my textfields Fname and Lname
//I can change my first and last name and hit button SAVE to save
public void actionPerformed(ActionEvent e)
if(e.getActionCommand().equals("SAVE")) submitChanges();
if(e.getActionCommand().equals("CHANGE_PASSWORD")) {
changepassword=new ChangePassword(new Frame(),name,badgeid);
public void submitChanges(){
String currentNTUsername = System.getProperty("user.name");
SimpleUser user =null;
try {
user = theABC.getID(ID);
user.setFirstName(txtFname.getText().trim());
user.setLastName(txtLname.getText().trim());
currentUser = user;
theABC.updateUserInfo(currentUser);
//IS this correctly if I want to use this method in singleton class ABC??
} catch(UserNotFoundException nfe)
JOptionPane.showMessageDialog(new JDialog(),"You have not yet registered",
"User Not Found",JOptionPane.WARNING_MESSAGE);
} catch(DelegateException de) {
JOptionPane.showMessageDialog(new JDialog(),"You have not yet registered",JOptionPane.ERROR_MESSAGE);
System.exit(0);
this.setVisible(false);
3) click on ChangePassword in my above GUI class A..will call this class B..and in this class B
I need to access method in a Singleton class- ABC class,,DO i need to inititates it agian, if not what should I do? thanks
package com.lockheed.vista.userinfo;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import javax.swing.table.*;
import javax.swing.tree.*;
import java.util.StringTokenizer;
import java.util.Vector;
import java.io.*;
import javax.swing.text.*;
import javax.swing.text.html.*;
import javax.swing.colorchooser.*;
import javax.swing.filechooser.*;
import javax.accessibility.*;
import java.beans.*;
import java.applet.*;
import java.net.*;
import org.apache.log4j.*;
import com.lockheed.common.gui.GraphicUtilities;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import vista.user.UserServicesDelegate;
import vista.user.SimpleUser;
import vista.user.UserNotFoundException;
import vista.user.*;
import com.lockheed.common.ejb.*;
import com.lockheed.common.gui.*;
import com.lockheed.vista.publish.*;
* This program allow users to change their Vista Web Center's password
public class ChangePassword extends JDialog
implements ActionListener{
protected final Logger log = Logger.getLogger(getClass().getName());
private UserServicesDelegate userServicesDelegate;
private User currentUser = null;
private JPasswordField txtPasswd, txtVerifyPW;
private JButton btnSubmit,btnCancel;
private JLabel lblName,lblBadgeID;
private String strBadgeID="";
* This is the constructor. It creates an instance of the ChangePassword
* and calls the method to create and build the GUI.
public ChangePassword(Frame owner,String name,String badgeid)
super(owner, "Change Password",true);
initScreen(name,badgeid);//build the GUI
* This method instantiates all the GUI widgets and places them into panels and
* onto the frame.
private void initScreen(String strname,String strBadgeid)
txtPasswd = new JPasswordField(20);
txtVerifyPW=new JPasswordField(20);
txtPasswd.setEchoChar('*');
txtVerifyPW.setEchoChar('*');
JPanel pnlMain=new JPanel();
pnlMain.setLayout(new BoxLayout(pnlMain, BoxLayout.Y_AXIS));
pnlMain.setBorder(BorderFactory.createEmptyBorder(20,0,20,0));
JPanel pnlPW=new JPanel();
pnlPW.setLayout(new BoxLayout(pnlPW, BoxLayout.X_AXIS));
pnlPW.setBorder(BorderFactory.createEmptyBorder(0,96,0,30));
pnlPW.add(new JLabel("Password:"));
pnlPW.add(Box.createRigidArea(new Dimension(5,0)));
pnlPW.add(txtPasswd);
JPanel pnlVerifyPW=new JPanel();
pnlVerifyPW.setLayout(new BoxLayout(pnlVerifyPW, BoxLayout.X_AXIS));
pnlVerifyPW.setBorder(BorderFactory.createEmptyBorder(0,63,0,30));
pnlVerifyPW.add(new JLabel("Verify Password:"));
pnlVerifyPW.add(Box.createRigidArea(new Dimension(5,0)));
pnlVerifyPW.add(txtVerifyPW);
JPanel pnlTop= new JPanel();
pnlTop.add(pnlPW);
pnlTop.add(Box.createRigidArea(new Dimension(0,10)));
pnlTop.add(pnlVerifyPW);
pnlMain.add(pnlTop);
btnSubmit = new JButton("Submit");
btnSubmit.setActionCommand("SUBMIT");
btnSubmit.addActionListener(this);
btnCancel = new JButton("Cancel");
btnCancel.setActionCommand("CANCEL");
btnCancel.addActionListener(this);
JPanel pnlBottom = new JPanel();
pnlBottom.setLayout(new BoxLayout(pnlBottom, BoxLayout.X_AXIS));
pnlBottom.setBorder(BorderFactory.createEmptyBorder(25,55,20,30));
pnlBottom.add(btnSubmit);
pnlBottom.add(Box.createRigidArea(new Dimension(25,0)));
pnlBottom.add(btnCancel);
pnlMain.add(pnlBottom);
this.setContentPane( pnlMain);
setSize(350,230);
setVisible(true);
public void actionPerformed(ActionEvent e)
if(e.getActionCommand().equals("CANCEL")) this.setVisible(false);
if(e.getActionCommand().equals("SUBMIT")) submitPW();
* This method is called when the submit button is clicked. It allows user to change
* their password.
public void submitPW(){
myABC= ABC.getABC();//Is this correct?
char[] pw =txtPasswd.getPassword();
String strPasswd="";
for(int i=0;i<pw.length;i++){
strPasswd=strPasswd+pw;
char[] vpw =txtVerifyPW.getPassword();
String strVerifyPW="";
for(int i=0;i<vpw.length;i++){
strVerifyPW=strVerifyPW+pw;
if((strPasswd==null)||(strPasswd.length()==0)) {
JOptionPane.showMessageDialog(new JDialog(),"You have not enter a password. Please try again.",
"Invalid Password",JOptionPane.ERROR_MESSAGE);
if((!strPasswd.equals(strVerifyPW)))
//password and verify password do not match.
JOptionPane.showMessageDialog(new JDialog(),"Your passwords do not match. Reenter and try again.",
"Invalid Password",JOptionPane.ERROR_MESSAGE);
try
myABC.setUserPassword(strPasswd);//try to use a method in Singleton class
txtPasswd.setText("");
txtVerifyPW.setText("");
this.setVisible(false);
} catch(DelegateException e) {
JOptionPane.showMessageDialog(new Frame(),
"Error.",
"Unable to change password information.",JOptionPane.WARNING_MESSAGE);
} catch(UserNotFoundException e) {
JOptionPane.showMessageDialog(new Frame(),
"Error.",
"Unable to change password information.",JOptionPane.WARNING_MESSAGE);
And ofcourse I have other EJB classes to work with these classes.
***It compiles okey but when I ran, it say "NullPointerException"
I think I call my Singleton wrong.
Please help me.thanks

1. When replying, use <reply>, don't post a new topic.
2. Implementing a singleton is a frequently asked question. Search before you post.
3. This is not a question about Swing. A more appropriate forum would be "New To Java Technology" or perhaps "Java Programming", but see point 1.
4. When posting code, keep it short. It increases the chance of readers looking at it. And in composing your shorter version for the forum, you just may solve your problem.

How to make Singleton Class secure

I have a Singleton class which I instantiate using reflection by a call to a public getInstance method that return the object from a private constructor. I have to use reflection as I dont have any other options since my class instantiation is decided on runtime. How will I secure other form instantiating the same class again by using reflection on my private constructor? Any ideas?

How much do these different implementations of your singleton have in common? What I'm getting at is, is there some common code you could extract out of them all, and make that a singleton in it's own right? Needing to do this sort of hacking is often a sign you're fudging something together, that could be solved more elegantly. We use the Singleton pattern generally when the state of the object needs to exist exactly once. Can you extract that from the disparate objects?
The singleton classes that I load do not have anything in common. They are all similar but unique, and independant in their own respect. I will have to decide only on what singleton object I have to load in runtime, based on certain criterion. This is done by reflection, by a call to the public getInstance() method of the respective singleton classes, since I am deciding on runtime. My problem is that can I prevent others from accessing my private constructor from outside the class using reflection, which enables them to create another duplicate object. Can I restrict them to use only my getInstance() method instead?? I know this is hacking to access the private members, but I want to know whether there is any way where I can restrict this hacking???In the above code I dont want these statements to work at any case
java.lang.reflect.Constructor[] c = cl.getDeclaredConstructors();
c[0].setAccessible(true);
A anotherA = (A) c[0].newInstance(new Object[]{"Duplicate"});

How to implement a singleton class across apps in a managed server}

Hi ,
I tried implementing a singleton class , and then invoking the same in a filter class.
Both are then deployed as a web app (war file) in a managed server.
I created a similar app , deployed the same as another app in the same managed server .
I have a logger running which logs the singleton instances as well.
But am getting two instances of the singleton class in the two apps - not the same .
I was under the impression that , a singleton is loaded in the class loader level , and since all apps under the same managed server used the same JVM , singleton will only get initialized once.
Am i missing something here ? or did i implement it wrong..?
public class Test
   private static Test ref ;
   private DataSource X;
   static int Y;
   long Z ;
   private Test ()
      // Singleton
       Z= 100 ;
   public static synchronized Test getinstance() throws NamingException, SQLException
      if(ref == null)
         ref = new Test() ;
         InitialContext ic = new InitialContext();
         ref.X = (DataSource)ic.lookup ("jdbc/Views");
      return ref ;
   public Object clone()throws CloneNotSupportedException
       throw new CloneNotSupportedException();
   public int sampleMethod (int X) throws SQLException
public final class Filter implements Filter
     public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException
          try
               Test ref = Test.getinstance();
               log.logNow(ref.toString());
}Edited by: Tom on Dec 8, 2010 2:45 PM
Edited by: Tom on Dec 8, 2010 2:46 PM

Tom wrote:
Hi ,
I tried implementing a singleton class , and then invoking the same in a filter class.
Both are then deployed as a web app (war file) in a managed server.
I created a similar app , deployed the same as another app in the same managed server .
I have a logger running which logs the singleton instances as well.
But am getting two instances of the singleton class in the two apps - not the same .Two apps = two instances.
Basically by definition.
>
I was under the impression that , a singleton is loaded in the class loader level , and since all apps under the same managed server used the same JVM , singleton will only get initialized once. A class is loaded by a class loader.
Any class loader that loads a class, by definition loads the class.
A VM can have many class loaders. And far as I know every JEE server in existance that anyone uses, uses class loaders.
And finally there might be a problem with the architecture/design of a JEE system which has two applications but which is trying to solve it with a singleton. That suggests a there might be concept problem with understanding what an "app" is in the first place.

How to ensure singleton classes no longer exist

hi all not sure if this is the right forum....
I am writting an application that integrates another, I wish to stop and then restart the integrated application but it seems that the singleton classes of which there are quite a few ( each being statically initalised) do not disappear when I try to shut them dowm. (if I am shutting them down that is ...)
is there a way to ensure these instances are terminated so I can restart the integrated application inside my application?
is there a way to see what instances exist so I can see if in fact I am disposing of any?
thanks for ur help

is there a way to ensure these instances are
terminated so I can restart the integrated application
inside my application?
is there a way to see what instances exist so I can
see if in fact I am disposing of any?
What exactly are you trying to achieve?
Do these hold on to resources which you must clean first? Then you must have a clean/dispose method. There is no other option. You can use a registration class to make this easier.
Do you simply want to reinitialize them? Then you could use a class loader but it probably going to take less time to simply do the same as above and add a reinit method to each. Again you can use a registration class to make this easier.

Singleton class within Container

Let me extend my apologies now if this is to simple of a question for the forum.
Here is my design issue. We are within a session bean (Stateless) and each session bean will need access to a Singleton class which possesses reference data (has a find method). This Singleton class must be static as we do not wish to replicate the amount of data involved.
Here is my concern. Based on the fact the EJB container has created 10 session beans which must access this Singleton class and the methods within it, I "think" there will be a concurrency issue with this design.
Can a EJB guru shade some light on this issue for me?
Thanks in advance!

If the the singleton class is used for multiple read and only one specific bean does a write, I dont think there should be a problem.
However, if there are multiple read and write scenarios, then offcourse concurrency is an issue.
What kind of data are using inside the single ton class. If you are using a hashtable or Vector inside, they take care of concurreny , as they are synchronized.
Or else another way I could think of is
Create a statefull session bean, instead of a java object for your singleton. Make the maximum and minimum cache size to 1.
This will take care of the object to be singleton. And the bean would take care of the concurreny.
Just my thoughts, am not an expert,

Singleton Class ArrayCollection within Flashbuilder (Mobile) empty?

Hi,
I am currently trying to implememnt a Singleton Class in order to store a ArrayCollection of items that I can then access and manipulate across the lifecycle of my app. I have created the below Singleton Class that is designed to hold the ArrayCollection information:
package valueObjects
    import mx.collections.ArrayCollection;
    [Bindable]
    public class Model
        private static var instance:Model = new Model();
        public var ids:ArrayCollection = new ArrayCollection();
        public function Model()
            if(instance)
                trace("New instance cannot be created. Use Singleton.getInstance()");
        public static function getInstance():Model
            return instance;
I have then created the following code on the Main Deafult page for my application so that the ArrayCollection is populated as soon as the app is initiated:
            import valueObjects.Model;
            protected var models:Model = new Model();
                        private function loop():void
                var index:int;
                for( index = 0; index < compsCollection.length; index++ )
                    trace( "Element " + index + " is " + compsCollection[index].comp_id );
                                models.ids.addItem(compsCollection[index].comp_id);
                    trace(models.ids.length);
The ArrayCollection in the Singleton Class is being populated as the trace statement that I have entered into the loop clearly shows the build of of data in the ArrayCollection. However then when I move to another view within the application I then try to access this ArrayCollection within the Singleton Class with the following code:
import valueObjects.Model;
protected var models:Model = Model.getInstance();
protected var test:ArrayCollection = new ArrayCollection();
protected function view1_viewActivateHandler(event:ViewNavigatorEvent):void
                var index:int;
                trace("Array Length =" + models.ids.length);
                for( index = 0; index < models.ids.length; index++ )
                    trace( "Element " + index + " is " + models.ids[index].comp_id );
                    test.addItem(models.ids[index].comp_id);
                testbox.text = test.toString();
Now the problem I am having is that when I try to access this ArrayCollection(ids) it appears to be empty for some reason. I have included a trace statement that also says that the length of the ArrayCollection is "0". Can anyone please help??

if your value object class change this
change this
public var ids:ArrayCollection = new ArrayCollection();
to
public static var ids:ArrayCollection = new ArrayCollection();
on your default page change this
models.ids.addItem(compsCollection[index].comp_id);
to
valueObjects.Model.ids.addItem(compsCollection[index].comp_id);
on your view change to something like this.
protected
function view1_viewActivateHandler():void
               //initialize="view1_viewActivateHandler();"
               var index:int;
               trace("Array Length =" + valueObjects.Model.ids.length);
               for( index = 0; index < valueObjects.Model.ids.length; index++ )
                    trace( "Element " + index + " is " + valueObjects.Model.ids[index].comp_id );
                    test.addItem(valueObjects.Model.ids[index].comp_id);
               //testbox.text = test.toString();
good luck let me know if you have any question i tested this and it worked like a charm for me.
Miguel

Singleton class nagas

hi,
can any tel how to write the singleton class with full example
for ex: for the class "Test" and how to use this in applications

http://www.javacoffeebreak.com/articles/designpatterns/
regards,
Manuel Leiria

Can not access the Instance Data of a Singleton class from MBean

I am working against the deadline and i am sweating now. From past few days i have been working on a problem and now its the time to shout out.
I have an application (let's call it "APP") and i have a "PerformanceStatistics" MBean written for APP. I also have a Singleton Data class (let's call it "SDATA") which provides some data for the MBean to access and calculate some application runtime stuff. Thus during the application startup and then in the application lifecysle, i will be adding data to the SDATA instance.So, this SDATA instance always has the data.
Now, the problem is that i am not able to access any of the data or data structures from the PerformanceStatistics MBean. if i check the data structures when i am adding the data, all the structures contains data. But when i call this singleton instance from the MBean, am kind of having the empty data.
Can anyone explain or have hints on what's happening ? Any help will be appreciated.
I tried all sorts of DATA class being final and all methods being synchronized, static, ect.,, just to make sure. But no luck till now.
Another unfortunate thing is that, i some times get different "ServicePerformanceData " instances (i.e. when i print the ServicePerformanceData.getInstance() they are different at different times). Not sure whats happening. I am running this application in WebLogic server and using the JConsole.
Please see the detailed problem at @ http://stackoverflow.com/questions/1151117/can-not-access-the-instance-data-of-a-singleton-class-from-mbean
I see related problems but no real solutions. Appreciate if anyone can throw in ideas.
http://www.velocityreviews.com/forums/t135852-rmi-singletons-and-multiple-classloaders-in-weblogic.html
http://www.theserverside.com/discussions/thread.tss?thread_id=12194
http://www.jguru.com/faq/view.jsp?EID=1051835
Thanks,
Krishna

I am working against the deadline and i am sweating now. From past few days i have been working on a problem and now its the time to shout out.
I have an application (let's call it "APP") and i have a "PerformanceStatistics" MBean written for APP. I also have a Singleton Data class (let's call it "SDATA") which provides some data for the MBean to access and calculate some application runtime stuff. Thus during the application startup and then in the application lifecysle, i will be adding data to the SDATA instance.So, this SDATA instance always has the data.
Now, the problem is that i am not able to access any of the data or data structures from the PerformanceStatistics MBean. if i check the data structures when i am adding the data, all the structures contains data. But when i call this singleton instance from the MBean, am kind of having the empty data.
Can anyone explain or have hints on what's happening ? Any help will be appreciated.
I tried all sorts of DATA class being final and all methods being synchronized, static, ect.,, just to make sure. But no luck till now.
Another unfortunate thing is that, i some times get different "ServicePerformanceData " instances (i.e. when i print the ServicePerformanceData.getInstance() they are different at different times). Not sure whats happening. I am running this application in WebLogic server and using the JConsole.
Please see the detailed problem at @ http://stackoverflow.com/questions/1151117/can-not-access-the-instance-data-of-a-singleton-class-from-mbean
I see related problems but no real solutions. Appreciate if anyone can throw in ideas.
http://www.velocityreviews.com/forums/t135852-rmi-singletons-and-multiple-classloaders-in-weblogic.html
http://www.theserverside.com/discussions/thread.tss?thread_id=12194
http://www.jguru.com/faq/view.jsp?EID=1051835
Thanks,
Krishna

[svn] 1384: Splitting DefineFont into the various DefineFont 1, 2, 3, etc SWF tag formats but retaining a common base DefineFont class so that embedded fonts are still retained as symbols for the SWF dictionary no matter what version of the SWF tag is us

Revision: 1384
Author: [email protected]
Date: 2008-04-24 07:54:58 -0700 (Thu, 24 Apr 2008)
Log Message:
Splitting DefineFont into the various DefineFont 1, 2, 3, etc SWF tag formats but retaining a common base DefineFont class so that embedded fonts are still retained as symbols for the SWF dictionary no matter what version of the SWF tag is used.
Also improving [Embed] so that it can recognize .TTC files as assets (previously these were only recognized through CSS @font-face rules).
QE: Yes, please add a test case for using [Embed] to embed fonts from a TTC file in addition to our tests for @font-face. Note that the AFEFontManager must be configured for this scenario.
Doc: No
Checkintests: Pass
Mxunit: AtEmbed Font suite: Pass
Modified Paths:
flex/sdk/trunk/modules/compiler/src/java/flex2/compiler/media/AbstractTranscoder.java
flex/sdk/trunk/modules/compiler/src/java/flex2/compiler/media/FontTranscoder.java
flex/sdk/trunk/modules/compiler/src/java/flex2/compiler/util/MimeMappings.java
flex/sdk/trunk/modules/compiler/src/java/flex2/tools/PreLink.java
flex/sdk/trunk/modules/swfutils/src/java/flash/fonts/CachedFontManager.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/Dictionary.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/MovieEncoder.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/TagDecoder.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/TagEncoder.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/TagHandler.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/TagValues.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/builder/tags/FontBuilder.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFont.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFontAlignZones.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFontInfo.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tools/SwfxPrinter.java
Added Paths:
flex/sdk/trunk/modules/swfutils/src/java/flash/fonts/DefineFont3Face.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFont1.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFont2.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFont3.java
flex/sdk/trunk/modules/swfutils/src/java/flash/swf/tags/DefineFont4.java
Removed Paths:
flex/sdk/trunk/modules/swfutils/src/java/flash/fonts/DefineFontFace.java

Running the script by python2 solves it for me:
su - mythtv -c "nice -n 19 python2 /usr/bin/tv_grab_nl_py --output ~/listings.xml"
Best regards,
Cedric

Serializing a class that implements the Singleton pattern

Hello,
I am relatively new to Java and especially to serialization so the answer to this question might be obvious, but I could not make it work event though I have read the documentation and the article "Using XML Encoder" that was linked from the documentation.
I have a class that implements the singleton pattern. It's definition is as follows:
public class JCOption implements Serializable {
private int x = 1;
private static JCOption option = new JCOption();
private JCOption() {}
public static JCOption getOption() { return option; }
public int getX() { return x; }
public void setX(int x) { this.x = x; }
public static void main(String args[]) throws IOException {
    JCOption opt = JCOption.getOption();
    opt.setX(10);
    XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(new FileOutputStream("Test.xml")));
    encoder.setPersistenceDelegate(opt.getClass(), new JCOptionPersistenceDelegate());
    encoder.writeObject(opt);
    encoder.close();
}Since this class does not fully comply to the JavaBeans conventions by not having a public no-argument constructor, I have create a class JCOptionPersistenceDelegate that extends the PersistenceDelegate. The implementation of the instantiate method is as follows:
protected Expression instantiate(Object oldInstance, Encoder out) {
       Expression expression = new Expression(oldInstance, oldInstance.getClass(), "getOption", new Object[]{});
        return expression;
}The problem is that the resulting XML file only contains the following lines:
    <java version="1.5.0_06" class="java.beans.XMLDecoder">
        <object class="JCOption" property="option"/>
    </java> so there is no trace of the property x.
Thank you in advance for your answers.

How about this:
import java.beans.DefaultPersistenceDelegate;
import java.beans.Encoder;
import java.beans.Expression;
import java.beans.Statement;
import java.beans.XMLEncoder;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class JCOption {
    private int x = 1;
    private static JCOption option = new JCOption();
    private JCOption() {}
    public static JCOption getOption() { return option; }
    public int getX() { return x; }
    public void setX(int x) { this.x = x; }
    public static void main(String args[]) throws IOException {
      JCOption opt = JCOption.getOption();
      opt.setX(10);
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      XMLEncoder encoder = new XMLEncoder( os );
      encoder.setPersistenceDelegate( opt.getClass(), new JCOptionPersistenceDelegate() );
      encoder.writeObject(opt);
      encoder.close();
      System.out.println( os.toString() );
class JCOptionPersistenceDelegate extends DefaultPersistenceDelegate {
    protected Expression instantiate(Object oldInstance, Encoder out) {
        return new Expression(
                oldInstance,
                oldInstance.getClass(),
                "getOption",
                new Object[]{} );
    protected void initialize( Class<?> type, Object oldInstance, Object newInstance, Encoder out ) {
        super.initialize( type, oldInstance, newInstance, out );
        JCOption q = (JCOption)oldInstance;
        out.writeStatement( new Statement( oldInstance, "setX", new Object[] { q.getX() } ) );
}   Output:
<?xml version="1.0" encoding="UTF-8"?>
<java version="1.5.0_06" class="java.beans.XMLDecoder">
<object class="JCOption" property="option">
<void property="x">
   <int>10</int>
</void>
</object>
</java>

Is it possible to increase the timeout on the properties dialog for LVOOP classes ?

I'm working on a medium scale application which has a lot of claases in it (it's got several largish Actor Framework based modules with quite a few possible messages). Recently it's gotten to the point that when I right click on a class to bring up the properties dialog, the dialog seems to take so long figuring out my class heirarchy that it times out and gives me the attached error.
I don't suppose there's any way of increasing the time out on the dialog ? (I suspect the fact that my laptop's hard disc speed has been crippled by my IT services encrypting it isn't helping me here...)
Gavin Burnell
Condensed Matter Physics Group, University of Leeds, UK
http://www.stoner.leeds.ac.uk/

Here is the modified VI, saved in LabVIEW 2012. Follow these steps to patch your system:
1. Close LabVIEW 2012.
2. Backup the following file: LabVIEW 2012\resource\Framework\Providers\VILibrary\libFrame_OpenPageRef.vi
3. Replace it with the version attached to this post.
4. Restart LabVIEW 2012.
Now you should no longer experience the 30 second timeout when the class property page loads. I set the timeout to "-1", so it should wait as long as necessary to open the page.
Note that if you ever repair or reinstall LabVIEW 2012, you'll need to patch this file again. Also, I wouldn't try patching any version other than 2012, since there may be other changes made to this VI across LabVIEW upgrades.
Darren Nattinger, CLA
LabVIEW Artisan and Nugget Penman
Attachments:
libFrame_OpenPageRef.vi ‏24 KB

(retain) properties in the singleton class

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