Serialization not working in one way

Question

I tried to serialize a String object from and to an applet. The servlet to applet communication is working properly. But applet to servlet serialization is not working, but no exceptions are thrown. Please help me. Thank you very much.(I have given the complete source code bellow)
=================================
APPLET SOURCE CODE
=================================
import java.net.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class TestApplet extends Applet {
Button send = new Button();
Button receive = new Button();
TextArea textarea = new TextArea();
BorderLayout borderLayout1 = new BorderLayout();
public void init() {
send.setLabel("send");
send.addActionListener(new Send_Listener());
receive.setLabel("receive");
receive.addActionListener(new Receive_Listener());
this.setLayout(borderLayout1);
this.add(send, BorderLayout.NORTH);
this.add(textarea, BorderLayout.CENTER);
this.add(receive, BorderLayout.SOUTH);
void sendObject(){
try{
URL url = new URL(getCodeBase(), "/servlets/testservlet");
URLConnection servletConnection = url.openConnection();
servletConnection.setDoInput(true);
servletConnection.setDoOutput(true);
servletConnection.setUseCaches (false);
servletConnection.setDefaultUseCaches (false);
servletConnection.setRequestProperty ("Content-Type", "application/octet-stream");
ObjectOutputStream outputToServlet = new ObjectOutputStream(servletConnection.getOutputStream());
outputToServlet.writeObject("some string here");
outputToServlet.flush();
outputToServlet.close();
textarea.append("aplet has send the object to the servlet\n");
}catch(Exception e){
textarea.append("EXCEPTION THROWN IN THE APPLET IN SENDOBJECT\n");
void getObject(){
try{
URL url =new URL(getCodeBase(), "/servlets/testservlet");
URLConnection servletConnection = url.openConnection();
servletConnection.setUseCaches (false);
servletConnection.setDefaultUseCaches(false);
ObjectInputStream inputFromServlet = new ObjectInputStream(servletConnection.getInputStream());
String aString=(String)inputFromServlet.readObject();
textarea.append(aString+"\n");
textarea.append("aplet has received the object from the servlet\n");
}catch(Exception e){
textarea.setText("EXCEPTION THROWN IN THE APPLET IN GETOBJECT\n");
class Send_Listener implements ActionListener{
public void actionPerformed(java.awt.event.ActionEvent e){
sendObject();
class Receive_Listener implements ActionListener{
public void actionPerformed(java.awt.event.ActionEvent e){
getObject();
===================================
SERVLET SOURCE CODE
===================================
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class TestServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try
ObjectOutputStream outputToApplet = new ObjectOutputStream(response.getOutputStream());
String aString= (String) request.getSession().getAttribute("ID");
outputToApplet.writeObject("this is the string object: "+aString);
outputToApplet.flush();
outputToApplet.close();
System.out.println("object send to applet:"+aString+"\n");
catch (IOException e)
System.out.println("EXCEPTION IN DOGET\n");
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
ObjectInputStream inputFromApplet = new ObjectInputStream(request.getInputStream());
String aString = (String) inputFromApplet.readObject();
request.getSession().setAttribute("ID", aString);
inputFromApplet.close();
System.out.println("object received from applet:"+aString+"\n");
catch(Exception e)
System.out.println("EXCEPTION IN DOPOST\n");

Answer 1

There are some things in Java which can't be serialized. When contained within a higher-level class such as Buttons. A button can be associated with an Action Listener. Now, you can serialize a button; however you can't serialize an action listener - for what should be to you obvious reasons. This is NOT an error and so there is no need to throw an exception when serializing the button.
Basically: Applet sends servlet button, but not listener.