Events in java..

1) how many types of events in java ?
2) which is the super class of all the event classes?
3) information about an event is stored in an instance of a subclass of an_______?
4) who sends events to java?

WAQAR_NAWAZ wrote:
1) how many types of events in java ?
2) which is the super class of all the event classes?
3) information about an event is stored in an instance of a subclass of an_______?
4) who sends events to java?God forgive.

Similar Messages

Send an event from Java Web Service to BPEL

Hi,
I have a requirement where from an Async BPEL service I have to call a Java Web Service. After the completion of its task Java Web Service will fire an event that has to be consumed by the BPEL to initiate further process. Can anybody help me with how to send an event from Java Web Service and at the same time consume it in BPEL?
Thanks,
Anuj

See the following posts for your answer
http://blogs.oracle.com/soabpm/entry/event_delivery_network_chapter
http://blogs.oracle.com/soabpm/entry/using_the_event_api_to_publish
http://guidoschmutz.wordpress.com/2010/01/12/using-the-event-api-to-publish-an-event-to-the-event-delivery-network-edn-the-spring-way/

Exception occurred during event dispatching:java.lang.NoSuchMethodError

Hello,
We have upgraded to the latest Oracle Application Server version 10.1.2.3.0 and the webutil version is 1.0.6.
But we face the following error while accessing the web link. Following message captured from Java Console.
Please suggest if you have any solutions/idea about this error. Thanks !
Oracle JInitiator: Version 1.3.1.22
Using JRE version 1.3.1.22-internal Java HotSpot(TM) Client VM
Maximum size: 50 MB
Compression level: 0----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
q: hide console
s: dump system properties
t: dump thread list
x: clear classloader cache
0-5: set trace level to <n>
Downloading http://si02938.in.irt.com:7778/forms/java/frmall_jinit.jar to JAR cacheDownloading http://si02938.in.irt.com:7778/forms/java/frmwebutil.jar to JAR cacheDownloading http://si02938.in.irt.com:7778/forms/java/jacob.jar to JAR cacheDownloading http://si02938.in.irt.com:7778/forms/java/FileInformation.jar to JAR cacheDownloading cacheproxyHost=nullproxyPort=0connectMode=HTTP, native.
Forms Applet version is : 10.1.2.3
Exception occurred during event dispatching:java.lang.NoSuchMethodError at oracle.forms.webutil.common.VBeanCommon.init(VBeanCommon.java:281) at oracle.forms.handler.UICommon.instantiate(Unknown Source) at oracle.forms.handler.UICommon.onCreate(Unknown Source) at oracle.forms.handler.JavaContainer.onCreate(Unknown Source) at oracle.forms.engine.Runform.onCreateHandler(Unknown Source) at oracle.forms.engine.Runform.processMessage(Unknown Source) at oracle.forms.engine.Runform.processSet(Unknown Source) at oracle.forms.engine.Runform.onMessageReal(Unknown Source) at oracle.forms.engine.Runform.onMessage(Unknown Source) at oracle.forms.engine.Runform.processEventEnd(Unknown Source) at oracle.ewt.lwAWT.LWComponent.redispatchEvent(Unknown Source) at oracle.ewt.lwAWT.LWComponent.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source)
Edited by: user12233243 on Nov 16, 2009 10:28 PM
Edited by: user12233243 on Nov 16, 2009 10:29 PM

hi
read the following configuration i hope it will help u.
How to get up and running with WebUtil 1.06 included with Oracle Developer Suite 10.1.2.0.2 on a win32 platform
Solution
Assuming a fresh "Complete" install of Oracle Developer Suite 10.1.2.0.2,
here are steps to get a small test form running, using WebUtil 1.06.
Note: [OraHome] is used as an alias for your real oDS ORACLE_HOME.
Feel free to copy this note to a text editor, and do a global find/replace on
[OraHome] with your actual value (no trailing slash). Then it is easy to
copy/paste actual commands to be executed from the note copy.
1) Download http://prdownloads.sourceforge.net/jacob-project/jacob_18.zip
and extract to a temporary staging area. Do not attempt to use 1.7 or 1.9.
2) Copy or move jacob.jar and jacob.dll
[JacobStage] is the folder where you extracted Jacob, and will end in ...\jacob_18
cd [JacobStage]
copy jacob.jar [OraHome]\forms\java\.
copy jacob.dll [OraHome]\forms\webutil\.
The Jacob staging area is no longer needed, and may be deleted.
3) Sign frmwebutil.jar and jacob.jar
Open a DOS command prompt.
Add [OraHome]\jdk\bin to the PATH:
set PATH=[OraHome]\jdk\bin;%PATH%
Sign the files, and check the output for success:
[OraHome]\forms\webutil\sign_webutil [OraHome]\forms\java\frmwebutil.jar
[OraHome]\forms\webutil\sign_webutil [OraHome]\forms\java\jacob.jar
4) If you already have a schema in your RDBMS which contains the WebUtil stored code,
you may skip this step. Otherwise,
Create a schema to hold the WebUtil stored code, and privileges needed to
connect and create a stored package. Schema name "WEBUTIL" is recommended
for no reason other than consistency over the user base.
Open [OraHome]\forms\create_webutil_db.sql in a text editor, and delete or comment
out the EXIT statement, to be able to see whether the objects were created witout
errors.
Start SQL*Plus as SYSTEM, and issue:
CREATE USER webutil IDENTIFIED BY [password]
DEFAULT TABLESPACE users
TEMPORARY TABLESPACE temp;
GRANT CONNECT, CREATE PROCEDURE, CREATE PUBLIC SYNONYM TO webutil;
CONNECT webutil/[password]@[connectstring]
@[OraHome]\forms\create_webutil_db.sql
-- Inspect SQL*Plus output for errors, and then
CREATE PUBLIC SYNONYM webutil_db FOR webutil.webutil_db;
Reconnect as SYSTEM, and issue:
grant execute on webutil_db to public;
5) Modify [OraHome]\forms\server\default.env, and append [OraHome]\jdk\jre\lib\rt.jar
to the CLASSPATH entry.
6) Start the OC4J instance
7) Start Forms Builder and connect to a schema in the RDBMS used in step (4).
Open webutil.pll, do a "Compile ALL" (shift-Control-K), and generate to PLX (Control-T).
It is important to generate the PLX, to avoid the FRM-40039 discussed in
Note 303682.1
If the PLX is not generated, the Webutil.pll library would have to be attached with
full path information to all forms wishing to use WebUtil. This is NOT recommended.
8) Create a new FMB.
Open webutil.olb, and Subclass (not Copy) the Webutil object to the form.
There is no need to Subclass the WebutilConfig object.
Attach the Webutil.pll Library, and remove the path.
Add an ON-LOGON trigger with the code
NULL;
to avoid having to connect to an RDBMS (optional).
Create a new button on a new canvas, with the code
show_webutil_information (TRUE);
in a WHEN-BUTTON-PRESSED trigger.
Compile the FMB to FMX, after doing a Compile-All (Shift-Control-K).
9) Under Edit->Preferences->Runtime in Forms Builder, click on "Reset to Default" if
the "Application Server URL" is empty.
Then append "?config=webutil" at the end, so you end up with a URL of the form
http://server:port/forms/frmservlet?config=webutil
10) Run your form.
If its Correct/Helpful please mark it thanks.
Sarah

Exception occurred during event dispatching:java.security.AccessControlExce

Hi,
I' m getting an error while connecting to database ORACLE 9i.
I'm using JDK 1.6.0
Actually the code is about how an Japplet connects to database ORACLE 9i
when i was connecting using normal program i had got the connection easily .
When i used this JApplet ,i'm getting this error.
CODE:
import java.awt.*;
import javax.swing.* ;
import java.sql.*;
import java.awt.event.*;
import java.util.*;
/*<applet code="jln" width=400 height=400></applet>*/
public class jln extends JApplet
public void init()
JTabbedPane jtp=new JTabbedPane();
jtp.addTab("View Marks",new VmPanel());
getContentPane().add(jtp);
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (Exception e)
{ e.printStackTrace();
System.out.println("Failed to load driver.");
class VmPanel extends JPanel implements ActionListener
JButton b1,b2;
TextArea ta1;
JTextField jtf1;
Connection con=null;
public VmPanel()
b1=new JButton("ok!");
b2=new JButton("clear");
ta1=new TextArea();
jtf1=new JTextField(10);
add(jtf1);
add(b1);
add(b2);
add(ta1);
b1.addActionListener(this);
b2.addActionListener(this);
public void actionPerformed(ActionEvent ae)
String str1=ae.getActionCommand();
if(str1=="ok!")
try
con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:jlngbldb", "scott", "tiger");
Statement stmt = con.createStatement ();
String ht=jtf1.getText();
System.out.println("\nHello\n");
ResultSet rs = stmt.executeQuery("SELECT * FROM jln WHERE ht='"+ht+"'");
while(rs.next())
ta1.setText ("");
ta1.setText("Name:"+rs.getObject("name")+"HallTicket:"+rs.getObject("ht")+"C.G:"+rs.getObject("cg")+"C.D:"+rs.getObject("cd")+"UNIX:"+rs.getObject("unix")+" S.T.M:"+rs.getObject("stm")+"N.N:"+rs.getObject("nn")+"I.S:"+rs.getObject("ins"));
rs.close();
stmt.close();
con.close();
catch(SQLException ex)
System.err.println("SQLException: " + ex.getMessage());
if(str1=="clear")
ta1.setText("");
jtf1.setText("");
if(str1==null)
ta1.setText ("");
ta1.setText("Please enter Hall Ticket Number above....");
}//action performed close
}//panel closed
AND THE ERROR IS:
Exception occurred during event dispatching:
java.security.AccessControlException: access denied (java.util.PropertyPermissio
n oracle.jserver.version read)
at java.security.AccessControlContext.checkPermission (AccessControlConte
xt.java:321)
at java.security.AccessController.checkPermission(AccessController.java:
546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:12
85)
at java.lang.System.getProperty(System.java:627)
at oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.ja
va:433)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:314)
at java.sql.DriverManager.getConnection(DriverManager.java:548)
at java.sql.DriverManager.getConnection(DriverManager.java :180)
at VmPanel.actionPerformed(jln.java:60)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:18
63)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.jav
a:2183)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel
.java:420)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased (BasicButtonL
istener.java:234)
at java.awt.Component.processMouseEvent(Component.java:5921)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3316)
at java.awt.Component.processEvent (Component.java:5686)
at java.awt.Container.processEvent(Container.java:1960)
at java.awt.Component.dispatchEventImpl(Component.java:4360)
at java.awt.Container.dispatchEventImpl(Container.java :2018)
at java.awt.Component.dispatchEvent(Component.java:4194)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4222
at java.awt.LightweightDispatcher.processMouseEvent (Container.java:3886)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3816)
at java.awt.Container.dispatchEventImpl(Container.java:2004)
at java.awt.Component.dispatchEvent (Component.java:4194)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:592)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:270)
at java.awt.EventDispatchThread.pumpEventsForFilter (EventDispatchThread.
java:198)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:171)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:166)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:158)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:119)
I'm getting this error when i pressed the OK! JButton.
PLEASE ! help me by correcting this error.
Thank You.

Presumably you are running this via a browser where the applet is served from the server.
Applets can only connect back to the origination server and using the name that the origination server was accessed with.
And that has nothing to do with JDBC, all connections work that way.
Your driver uses a connection thus it will not work unless it attempts to connect to the server that originated the applet.
Solutions
1. Connect to the server
2. Sign the applet
3. Modify the policy file of each client that will run the applet. This is not a good idea in an unsecure network.
Note as well that in an unsecure network is most often a bad policy to have an applet directly accessing a database regardless.

Non-gui/swing event in java possible ?

Dear Members :
Is it possible in java to raise and catch business events, as is possible in other languages, I know.
For instance - when I create a vehicle instance, that will trigger an event which will add that vehicle to vehicle_list(List) - something like that ? I am aware of Observer/Observable, but that is only if the source changes.
Could someone please explain with syntax if that's possible, I mean, tackling any kind of business events in java ?
Thanks in advance
Atanu

There is no out of the box event model... and be careful how you phrase these things... and in you are pedantic enough the pattern reveals itself.
What notifies the sales people that a new car is ready? It's not the Car itself is it? How about the factory? You're getting warmer... Who else does the factory tell? Maybe the tax man?
Yeah... Observe/r/able was a good first thought.
And... You might want to look into the Spring framework... I think you're groping for AOP.
Cheers. Keith.

How to handle doubleclick mouse event in java

i want to handle double click mouse event in java
i use getClickCount() function
but i want that on onetime click show othere windows
and on doubleclick show diif. window
but problem is that onetime is occuer always if u click doubleclick

Maybe post some code so we can see what, if anything, you are doing wrong.
Examing the results of a call to getClickCount() is the correct way to detect a double click.

Exception occurred during event dispatching: java.lang.UnsatisfiedLinkError

Hi,
Greetings. I am watching the following error in linux. I greatly appreciate your help.
Thanks
Rajkumar
Exception occurred during event dispatching:
java.lang.UnsatisfiedLinkError: no test in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1517)
at java.lang.Runtime.loadLibrary0(Runtime.java:788)
at java.lang.System.loadLibrary(System.java:834)
at test.<clinit>(test.java:3)
at Test.action(Main27.java:926)
at java.awt.Component.handleEvent(Component.java:5341)
at Test.handleEvent(Main27.java:1023)
at java.awt.Window.postEvent(Window.java:1614)
at java.awt.Component.postEvent(Component.java:3895)
at java.awt.Component.dispatchEventImpl(Component.java:3631)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:480)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:141)
at java.awt.Dialog$1.run(Dialog.java:542)
at java.awt.Dialog$3.run(Dialog.java:569)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Dialog.java:567)
at Main27.first(Main27.java:67)
at Main27.action(Main27.java:163)
at java.awt.Component.handleEvent(Component.java:5341)
at java.awt.Component.postEvent(Component.java:3885)
at java.awt.Component.postEvent(Component.java:3895)
at java.awt.Component.postEvent(Component.java:3895)
at java.awt.Component.dispatchEventImpl(Component.java:3631)
at java.awt.Component.dispatchEvent(Component.java:3477)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:480)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)

In your test.java (Which must be yours, since all serious classes have capitalised names) you are trying to load a JNI library with
static {
System.loadLibrary("test");
}Somewhere you should have a library file, I think called libtest.so, but the JVM can't find it.
Find out where it is and put -Djava.library.path=<the directory>
on the java command.

Traping all Events with Java App

Is it possible to trap all mouse event from Java code even when the java app is not in focus? Lets say a VB app is running and then Java needs to know that that VB app has been clicked?
ANy useful tip on this?

Is it possible to trap all mouse event from Java code
even when the java app is not in focus? No.
You will have to do this with native code.

Portal eventing between Java WD iview to ABAP WD iview?

HI Experts ,
I have requirement on which,
The manager can select an employee from the EE Search iView (Object and Data Provider). All other iViews react on the selection and display data of the selected employee. Technically the personnel number is transferred from the search iView to the other iViews on the portal page, also to the related activity iView. This mechanism is called Eventing. The applications, started via the related activity iView, are launched with the personnel number as parameter. With other words the application, e.g. Manage Objects on Loan, can be directly started for the employee selected from the EE Search iView.
The Employee Information page is based on WD Java whereas the Objects on Loan application described in this specification is based on WD ABAP...........Due to different technologies used how to do the Pernr number transfer between these iviews?
If anybody have done this let me know the steps
Thanks in Advance,
Dharani

Hi Dharani,
You can use portal events to enable iViews running on the same page to communicate with each other. You just have to find out which event is fired by the WD Java iView and then you will have to register and handle the event in your WD ABAP application : http://help.sap.com/saphelp_nw70ehp1/helpdata/en/f6/7d6f4151dc5758e10000000a1550b0/frameset.htm
You can use HttpFox (firefox plug-in) to find the details of the fired event (name, namespace...) by looking at the eventQueue parameter in the HTTP POST request.
Regards,
Pierre
Edited by: Pierre DOMINIQUE on Jul 9, 2009 11:16 AM

My own EVENTS in java

is it at all posible in java to create you own event s. and have listeners for them like the one ActionListener has the method actionPerformed(ActionEvent e) can i make my own methods that are triggered by events
and are only called if a new event is generated. like this method it is only called if the use clickes a button.
if there is a way could you please tell or show me how.
many thanks

Hi,
"Events" are an application of the observer pattern, usually implemented with the event generator idiom in Java. Please see full example in this detailed article.
http://www.javaworld.com/javaworld/jw-09-1998/jw-09-techniques.html

Client side event between Java iView and BSP application

Hi,
I am developing a BSP iView which listen to event raised by standard SAP HR TeamViewer iView. The TeamViewer iView raise a event when user click on the employee list.
EPCM.raiseEvent { "urn:com.sap.pct.hcm.orgmanagement:CurrentObject", "objectChanged", concatenatedKey);
My BSP is subscribing to the event and perform the myreceiveEvent function.
EPCM.subscribeEvent
( "urn:com.sap.pct.hcm.orgmanagement:CurrentObject", "objectChanged", myreceiveEvent );
However, my BSP returns an error message saying that EPCM is undefined. I know that I have to included the java script file. I checked with my basis team guy and they said there is not any js file in ICF. Can someone let me know which file I need to include in my BSP code and where is the file locate?
Thanks,
Eric

Hi Eric,
> the ICF where the BSP is stored
> is in the Oracle database
Eric... the place where the JS fragment - within the BSP - appears, is retrieved by some http request. The script=epcfproxy.js forces the browser to send a http request just to the same relative location the original page came from. Doesn't matter if something is within a database...
> Do you know how to locate the
> epcfproxy.js file in the WAS?
I think:
> and the epcfproxy.js file is in the zip file
> that you suggested
you have found it?! Put it to any place on the BSP server you can access, if you can't set it with relative url, use "/some/.../dir/epcfproxy.js" as location.
> If I am only EPCM but not EPCMPROXY,
> do I need to include the epcfproxy.js in my code?
Have a look at epcfproxy.js. It's no magic at all, you have to call top or parent (just look) and do some minor things. For sure, you can live without the proxy file, you have just to put the neede scripts explicitely on your page, that's not that fine, but it works.
Hope it helps
Detlev

Handling User Events in Java Server Pages

Is it possible to write and associate scripts with User Interface Events on an HTML front end and JSP back end.
THis is for JDeveloper3.0

The proper way to do this is by using
JavaScript.
One of my favorite ways to see this is by
visiting various web sites and when you
see something you like, using Netscape,
you can right click on the page and select
View Source, this will show you the source
for the page which may contain the
Java Script you are looking for.
The other way to do this is to use an Applet.
I hope this helps,
John@Oracle JDeveloper Team http://technet.oracle.com
null

Non-GUI events in Java

I was wondering how I would have to go about writing an event handling mechanism on something that is not GUI-based (non-AWT/SWING)!
Supposing one wanted to write an event listener that would tell them when a data structure is updated - e.g: in a typical producer-consumer model, where the consumer is to be notified of fresh entries whenever a producer writes integers to some data structure...
Does Java have classes/methods to handle such non-GUI-based 'events'? Is this a commonly found scenario in Java programming?
Thank you!

What you're looking for is the Observer-interface. Check out http://java.sun.com/j2se/1.4/docs/api/java/util/Observer.html
and
http://java.sun.com/j2se/1.4/docs/api/java/util/Observable.html

Attaching window system tray icon events to java frame

I need to bring java frame to front on an event with the icon placed in the system tray. Like if I click the mouse on it.. the frame should come to front.
Any body who can help, I will really appreciate.
Thanks in advance
Zeeshan

I am very interested in implementing just such a thing with my Java application. I am in the starting phases of this project and ran across your post in my search for info.
How much do you already have implemented? I.E., can you display the icon but are just having trouble catching the events for when the icon is clicked? Or do you not even have the ability to display the icon yet? I have found the Windows documentation on the MSDN site for the shell function Shell_NotifyIcon(), which is what we want to use but I have not begun any attempts to use it yet.
If you (or anyone else) have any info or have had any success at all with this yet, I would be very interested in hearing how it works. I'll be happy to share any info I find, when/if I get that far.
Thanks,
j

Translating Visual Basic Events into Java Events

I'm in the process of porting a Visual Basic application to Java. Now, most of it is pretty straight forward, since good OO practice is evident in the original VB source. With a good dose of refactoring along the way the Java version is looking pretty good too.
However, I'm having a problem with events. Here's a snuppet of one of a VB class that generates events and one that uses it:
(Invoices.cls)
-=-=-=-=-=-=-=-=-
Event AddItem(ItemID as String)
Event RemoveItem(ItemID as String)
Private m_Items as Collection
Public Sub Add(ItemID as String)
   m_Items.Add ItemID
   RaiseEvent AddItem(ItemID)
End Sub
Public Sub Remove(ItemID as String)
   m_Items.Remove ItemID
   RaiseEvent RemoveItem(ItemID)
End Sub
-=-=-=-=-=-=-=-=-and
(OrderBook.cls)
-=-=-=-=-=-=-=-=-
Private WithEvents m_Invoices as Invoices
Private Sub m_Invoices_AddItem(ItemID as String)
   CalculateTotals
End Sub
Private Sub m_Invoices_RemoveItem(ItemID as String)
   CalculateTotals
End Sub
-=-=-=-=-=-=-=-=-Can anyone give me a few pointers on what the Java equivalent to this VB code is?
Thanks,
Vince.

Hi,
There are few main things involved in a Java event delivery
1. The event source
2. The event listener
3. The even data
4. Registration
5. The event delivery process
I don't know the VB syntax, but any way it gives a good idea of what you wish to achieve.
Here the Invoice class is basically the event source. And the OrderBook class is the event listener. To proceed further you will have to specify (define) the event listener first. Secondly you will have to create an event object which contains the data to be delvered via the event.
1. Specifying the event listener interface
public Interface ItemOperationListener
public void itemAdded (ItemOperationEvent ioe);
public void itemRemoved (ItemOperationEvent ioe);
2. The event class
public class ItemOperationEvent extends java.util.EventObject
String item = null;
public ItemOperationevent(Object source, String Item)
super(source);
this.item = item;
public String getItem()
return item;
3. Creating and firing the event from the event source.
public class Invoice
private collection items; // any collection
// to hold all the event listeners , this way u can define > 1
// listeners
javax.swing.event.EventListenerList listenerList = new javax.swing.event.EventListenerList();
public void addItem(String item)
items.add(item);
// update the listeners
fireItemAdded(item);
public void removeItem(String item)
items.add(item);
// update the listeners
fireItemRemoved(item);
public void addItemOperationListener(itemOperationListener ioe)
listenerList.add(ioe);
public void removeItemOperationListener(itemOperationListener ioe)
listenerList.remove(ioe);
public void fireItemAdded(String item)
ItemOperationEvent e = null;
Object[] listeners = listenerList.getListenerList();
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners== ItemOperationListener.class) {
if (e == null)
e = new ItemOperationEvent(this,item);
((ItemOperationlistener)listeners[i+1]).itemAdded(e);
public void fireItemRemoved(String item)
ItemOperationEvent e = null;
Object[] listeners = listenerList.getListenerList();
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i] == ItemOperationListener.class) {
if (e == null)
e = new ItemOperationEvent(this,item);
((ItemOperationlistener)listeners[i+1]).itemRemoved(e);
4. The listener and the registration .
public class OrderBook implements ItemOperationListener
private Invoice invoice; // invoice instance.
public OrderBook()
// register for event updates .
invoice.additemOperationListener(this);
public void itemAdded(ItemOperationEvent ioe)
String tobeAdded = ioe.getItem();
calculate();
public void itemRemoved(ItemOperationEvent ioe)
String tobeRemoved = ioe.getItem();
calculate();
public void calculate()
I hope this gives a picture of the standard method of event delivery in java . However you can even follow the Observer, Observable pattern (see the documentation for java.util.Observer, Observable).
Hope this helps,
Manish.

Events in java..

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