Example class that implements Serializable interface

Dear,
I have a class myData that I want to implement Serializable interface. class myData has only two fields: Integer iData1, String sData2.
Could anybody shown me how my myData class should be?
Thanks a lot!

Hey, if you have yet to obtain a remote reference from the app server ...then we are into pandora's box. I lost three whole heads of hair getting up on JBoss when I first started. You want to check out the JBoss forums on the JBoss website, and the enterprise javabeans forum here. Search some posts and read the free JBoss manual.
Unfortunately, there isn't a 'here, do this' solution to getting connected with JBoss. There are quite a few gotcha's. There are descriptors, descriptor syntax ...and this changes between releases so there seems to be alot of people saying 'here, do this' ...but you try and it doesn't work (wrong release). Here are some descriptors that I threw up recently for someone ...a place to start.
http://forum.java.sun.com/thread.jsp?forum=13&thread=414432
This drove me nuts until it all worked right. I was stuck for three weeks at one point ...ready to give up, but then I got it. Perservere ...its a nice container for learning in (its free!).
I will try and watch for you.
Oh, and put something in your head ...at least then you will keep your hair !
:)

Similar Messages

Modifying a Class that implements Serializable

I have a class LDAPUser
import java.io.*;
public class LDAPUser implements java.io.Serializable{
     private java.lang.String name;
     private java.lang.String userID;
     private java.lang.String associateNumber;
public LDAPUser() {
     super();
public boolean equals(Object o) {
     if (o == this)
     return true;
     if (!(o instanceof LDAPUser))
     return false;
     return (((LDAPUser)o).getAssociateNumber().equals(this.getAssociateNumber()));
public java.lang.String getAssociateNumber() {
     if(associateNumber == null){
          return getUserID();
     return associateNumber;
public java.lang.String getName() {
     return name;
public java.lang.String getUserID() {
     return userID;
public void setAssociateNumber(java.lang.String newAssociateNumber) {
     associateNumber = newAssociateNumber;
public void setName(java.lang.String newName) {
     name = newName;
public void setUserID(java.lang.String newUserID) {
     userID = newUserID;
It works fine.
I needed to add functionality to it. These were the modifications.
private java.lang.String distinguishedName;
private boolean validUser;
public java.lang.String getDistinguishedName() {
     return distinguishedName;
public boolean isValidUser() {
     return validUser;
public void setDistinguishedName(java.lang.String newDistinguishedName) {
     distinguishedName = newDistinguishedName;
public void setValidUser(boolean newValidUser) {
     validUser = newValidUser;
I am using visual age for java and in the Test environment the changes work fine.
When I promote the changes to our application server (websphere) the changes are not there. I get a method not found error and though trial and error have identified that the server is not actually using the class from the jar. I have removed any other occurences of the class from the server.
My question is if I change a Serializable class how do I make those changes take affect (thorough better coding) and for right now, where is this "old instance" of my class coming from and how do I get rid of it.
Thanks in Advance,
Jason Grieve

If the server is running than the class might be already loaded through the class loader, so it wont be load again.
this unless you use hot deployment, which you have to figure how it is being handled in your srver.
Doron

HELP?! a class that implements ..... : java.util.Vector

My instructions say this:
In the constructor, create the collection object (Since java.util.List is an interface, you will need to instantiate a class that implements this interface: java.util.Vector or java.util.LinkedList or java.util.ArrayList).
I know, this IS a homework assignment - I am not sure how to go about this. I DO have code so far up to this point, can anyone help?
import dLibrary.*;
import java.awt.Color;
* @author Rob
* @version 8/18/03
public class PhrasesII extends A3ButtonHandler
        private A3ButtonWindow win;
        private ATextField stringAcceptor;
        private ALabel listOstrings;
        private ALabel inputString;
        private ALabel status;
        private java.awt.List display;
        private java.util.List collection;
public PhrasesII()
        win = new A3ButtonWindow(this);
        stringAcceptor= new ATextField (50,420,200,25);
        stringAcceptor.place(win);
        listOstrings = new ALabel(100, 10, 100, 380);
        listOstrings.setFontSize(10);
        listOstrings.setText("List of Strings:");
        listOstrings.place(win);
        inputString = new ALabel(50,400,200,25);
        inputString.setFontSize(10);
        inputString.setText("Input String:");
        inputString.place(win);
        display = new java.awt.List();
        display.setLocation(200, 100);
        display.setSize(200, 250);
        display.setBackground(Color.lightGray);
        win.add(display, 0);
        win.setLeftText("Save");
        win.setMidText("Display");
        win.setRightText("Discard");
        win.repaint();
public void leftAction()
    public void midAction()
    public void rightAction()

I am getting a " can't resolve symbol" when I do thisYou have to either import java.util.ArrayList or specify it fully, e.g., "new java.util.ArrayList()".
Is that the line that is causing you problems? The error message should give the line number.
my instructions also say I have to use "interface
java.util.List when declaring your reference" so I am
confused about using "= new ArrayList();"What they're saying is that you want code like this:
private java.util.List frogs;    // this is the reference declaration
//... later on...
frogs = new java.util.ArrayList(); // this isn't a declarationWhat this means is that when you declare a field or variable, you should declare its type to be an interface.
But when you actually instantiate a value for that variable, then you should use a concrete class that implements that interface. (You have to; interfaces can't be instantiated.)
This is good programming style for reasons I don't have the space to explain here.

Using a class or servlet that implements Serializable

Hello everyone,
Can someone please help me. I need to make a program that uses a class or servlet that implements Serializable and then use the values of the variables in servlets.
The first is using it to validate login. then changing the color of the background, header and footer of each servlet.
the variables in the Serialized file are all Strings for color, username, password, header text and footer text.
I tried using the applet tag to run the class in the servlet but it is not working.

It's not working because you seem to be making random guesses what servlets, serialization and files are

Concrete classes implement abstract class and implements the interface

I have one query..
In java collection framework, concrete classes extend the abstract classes and implement the interface. What is the reason behind extending the class and implementing the interface when the abstract class actually claims to implement that interface?
For example :
Class Vector extends AbstractList and implements List ,....
But the abstract class AbstractList implements List.. So the class Vector need not explicitly implement interface List.
So, what is the reason behind this explicit definition...?
If anybody knows please let me know..
Thanx
Rajendra.

Why do you post this question again? You already asked this once in another thread and it has been extensively debated in that thread: http://forum.java.sun.com/thread.jsp?forum=31&thread=347682

Transform a class that implements JPanel into a bean.

I'd to create a bean, from a class that implements JPanel, that in fact is a custom component.
How can I create a bean?
I have absolutely no idea about beans.
What can make beans for me?
I know a lot about the theory of ejb, is this what I need?
I'm quite confused, please make me see the light!!!!!
Thanks.

Hi Daniel!
To answer your question short as possible:
Java -Beans are reusable code - components,
similar to VB Active -X components,
which you can use when developing your own
applications.
Beans can have a graphic user interface, so you
can use builder tools like JBuilder or Beanbox
to show them graphically in a designer.
You can modify them about their properties,
mostly shown in a special property window of a
builder tool.
It's really not very hard to create your own beans,
the only thing you have to do is to pack all the
classes which make the bean into a jar file.
Then you can import the bean with the builder
and it will be shown.
The jar manifest file needs to look like for example:
Manifest-Version: 1.0
Name: BeanClock.class
Java-Bean: True
All the properties are implemented by public property-get
and property-set methods, in order to show them in the property window.
Java is doing that by introspection.
Hope, this makes it a little bit clearer for you!

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>

How to find out in program which all classes have implemented an interface

Hello,
I have created an interface and few classes are implementing the interface.
I want to know in a program which all class have implemented the interface.
Is it possible to find it out and how?
Regards,
Bikash.

Hi Bikash,
Read the Database view VSEOIMPLEM with where condition REFCLSNAME = Interface Name and version = 1.
This would give you all the classes which have implemented the interface and are active...
If you want to look at the values that the field version can have then see Type Group SEOC ans search for version....
Hope this help...
Regards,
Sitakant

Why we require to implement Serializable interface?

Hi techies,
I am new to Serialization. Why we require to use Serializable interface for Serializing objects. Since Serializable interface is a marker interface, how it prevents objects not implementing Serializable from being Serialized. Does Java Compiler checks it or how it checks it?

JavaBreather wrote:
Since Serializable interface is a marker interface, how it prevents objects not implementing Serializable from being >Serialized. Does Java Compiler checks it or how it checks it?Compiler does nothing but mark the class as implementing the interface. You can then later check whether objects instanceof Interface" and find out whether or not it is present. As said above, ObjectOutputStream does the same thing.
Marker interfaces are a misuse of interfaces, and should be avoided. You shouldn't create new ones.Annotations introduce in Java 5 are a generic mechanism of adding metadata to a class.

Reflect the class that implements Runnable

Hi,
I am implementing the reflection of the class that implements Runnable. In order to start a new thread I am trying to invoke "start()" method ( which is obviously not defined my class ) and I therefore I am getting "java.lang.NoSuchMethodException".
I am wondering is it possible at all to start a new thread on a reflected class?
thanks in advance.
{ Class refClass = Class.forName(className);
String methodName = "start";
Class[] types = new Class[1];
types[0] = Class.forName("java.util.HashMap");
Constructor cons = refClass.getConstructor(types);
Object[] params = new Object[5];
params[0] = new HashMap();
Method libMethod = refClass.getMethod(methodName, null);
libMethod.invoke(objType, null); }

Well, if we knew what it meant to "start a thread on a class" we could probably figure out how to "start a thread on a reflected class". If we knew what a "reflected class" was, that is.
In other words, it would help if you rephrased your question using standard terminology (and also explained why you want to do whatever it is you want to do).
But let's guess for now: If you have an object which implements Runnable then you start a thread to run that object like this:
Runnable r = // some object which implements Runnable
new Thread(r).start();Not what you wanted? Go ahead and clarify then.

Class constructor that implements an interface returns an "interface", why

Hi,
I am studying some code that I need to understand well. This code works, I just don't understand the following:
A class was defined extending an interface as so:
public class GeometricShape implements Area {
// constructor
public GeometricShape() {
System.out.println('bla);
In another file, GeometricShape class was instantiated as follows:
public class ExampleUse {
Area g = new GeometricShape();
My qustion is, why does the code above expects "new GeometricShape()" constructor to return an interface of type Area?
Can someone explain?
thanks

Can someone explain?When a class implements an interface, or extends another class, or when a interface extends another interface, it means that anywhere an instance of the parent class or interface is expected, the child can be used.
Wherever a Mammal is expected, you can provide a Dog or Cat or Whale or Human or NakedMoleRat. Each of those is a mammal.
If you say "give me some food," and you don't specify anything else, the person you're talking to can hand you a hamburger or an apple or a bowl of rice. Any of those will meet the requirements you put forth.
This is how the OO "is-a" relationship maps to Java.

Abstract Class that implements Comparable

I am trying to understand how a comparable interface works with an abstract class. Any help is greatly appreciated.
I have a class ClassA defined as follows:
public abstract class ClassA implements Comparable I have a method, compareTo(..), within ClassA as follows:
public int compareTo(Object o) I have a sub-class ClassB defined as follows:
public class ClassB extends ClassAI am receiving a compile error:
Class must implement the inherited abstract method packagename.ClassA.compareTo(Object)
Should or can the compareTo be abstract in ClassA and executed in ClassB? Just not sure how this works.

???? if you are inheriting from an abstract class your subclass must implement methods that were declared in the parent (abstract) class but not implemented
When in doubt, refer to the Java Language Specification..

How can I know a class which implements Runnable interface has terminated?

Hello! I have a class which has implements Runnable interface, while I want to execute some operation when the thread has terminate in multithread enviroment.How can I know the thread has terminated?Does it give out some signal?Cant I just call my operation at the end of the run() method?

I want to execute some operation when
the thread has terminate in multithread enviroment....
Cant I just call my operation at the end
of the run() method?Sure. Before run() ends, invoke that other operation.
How
can I know the thread has terminated?Does it give out
some signal?Not that I'm aware of, but you can do what you described above, or I believe a different object can call isAlive on the thread.

How to get classes which implement the interface in program

Hi,
I created an interface and some classes are implementing it. I want to know in which classes the interface is implemented through program. I mean in which table the interface implemented details stores.
please helps regarding this.
Thanks,
Regards,
Priya

Hi.,
Read the database view VSEOIMPLEM with where condition., REFCLSNAME = <Interface Name> and Version = 1.
This gives the class names which implement the interface.,
hope this helps u.,
Thanks & Regards,
Kiran

Question about methods in a class that implements Runnable

I have a class that contains methods that are called by other classes. I wanted it to run in its own thread (to free up the SWT GUI thread because it appeared to be blocking the GUI thread). So, I had it implement Runnable, made a run method that just waits for the thread to be stopped:
while (StopTheThread == false)
try
Thread.sleep(10);
catch (InterruptedException e)
//System.out.println("here");
(the thread is started in the class constructor)
I assumed that the other methods in this class would be running in the thread and would thus not block when called, but it appears the SWT GUI thread is still blocked. Is my assumption wrong?

powerdroid wrote:
Oh, excellent. Thank you for this explanation. So, if the run method calls any other method in the class, those are run in the new thread, but any time a method is called from another class, it runs on the calling class' thread. Correct?Yes.
This will work fine, in that I can have the run method do all the necessary calling of the other methods, but how can I get return values back to the original (to know the results of the process run in the new thread)?Easy: use higher-level classes than thread. Specifically those found in java.util.concurrent:
public class MyCallable implements Callable<Foo> {
public Foo call() {
return SomeClass.doExpensiveCalculation();
ExecutorService executor = Executors.newFixedThreadPool();
Future<Foo> future = executor.submit(new MyCallable());
// do some other stuff
Foo result = future.get(); // get will wait until MyCallable is finished or return the value immediately when it is already done.

Example class that implements Serializable interface

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