Passing custom Objects from applet to servlet

I have a servlet and i want to pass through UrlConnection some objects. When I tested it, it worked fine. When I passed Java native objects (String, File..). But when I try to pass my own Object (instance of my own Class), Object is sent into Servlet correctly via ObjectOutputStream but when I wanted to restore object in servlet side it doesn't work. it throws exceptions that My class was not found.

I have MyObject class in project with applet where is loaded and sent to servlet and then i have MyObject class in my servlet package too... So where I must place MyObject class to work it?

Here is my applet code which send MyObject instance to servlet via URLConnection

  URLConnection con = null;
        ObjectOutputStream outputToServlet = null;
        ObjectInputStream inputFromServlet = null;
        MyObject my = new MyObject("200");
//open Url connection
        con = CommunicationAgent.openConnectionWithServlet(CommunicationAgent.setUrlForServletConnection());
        con.setDefaultUseCaches(false);
        con.setDoOutput(true);
        con.setDoInput(true);

// creating ObjectOutputStream
        try {
            outputToServlet = new ObjectOutputStream(con.getOutputStream());
        } catch (IOException ex) {
            Logger.getLogger(SoundAppletSimpleVersion.class.getName()).log(Level.SEVERE, null, ex);
        }

//Send MyObject instance to server      
        try {
            outputToServlet.writeObject(my);

        } catch (IOException ex) {
            Logger.getLogger(SoundAppletSimpleVersion.class.getName()).log(Level.SEVERE, null, ex);
        }

Here is code from my servlet, easy take stream from request object and then I want to copy incoming object to MyObject instance in servlet. Here is a problem and exception is thrown

ObjectInputStream input = new ObjectInputStream(request.getInputStream());
        MyObject my = null;
        try {
            my = (MyObject) input.readObject();
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(Servlet.class.getName()).log(Level.SEVERE, null, ex);
            System.out.print("nepovedlo se precist objekt");
        }

Exception thrown in Tomcat

INFO: Reloading Context with name [/Rozhlas_jsf] is completed
XII 04, 2012 3:43:22 DOP. Servlets.Servlet processRequest
SEVERE: null
java.lang.ClassNotFoundException: SoundApplet.MyObject
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1711)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1556)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:622)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1593)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1514)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1750)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1347)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
    at Servlets.Servlet.processRequest(Servlet.java:42)
    at Servlets.Servlet.doPost(Servlet.java:120)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

and from Javaconsole

network: Connecting http://localhost:8084/Rozhlas_jsf/Servlet with proxy=DIRECT
XII 04, 2012 3:44:26 DOP. SoundApplet.SoundAppletSimpleVersion jButton8ActionPerformed
SEVERE: null
java.io.IOException: Server returned HTTP response code: 500 for URL: http://localhost:8084/Rozhlas_jsf/Servlet
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at SoundApplet.SoundAppletSimpleVersion.jButton8ActionPerformed(SoundAppletSimpleVersion.java:708)
    at SoundApplet.SoundAppletSimpleVersion.access$1000(SoundAppletSimpleVersion.java:27)
    at SoundApplet.SoundAppletSimpleVersion$12.actionPerformed(SoundAppletSimpleVersion.java:371)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.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.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$000(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Exception in thread "AWT-EventQueue-3" java.lang.NullPointerException
    at SoundApplet.SoundAppletSimpleVersion.jButton8ActionPerformed(SoundAppletSimpleVersion.java:717)
    at SoundApplet.SoundAppletSimpleVersion.access$1000(SoundAppletSimpleVersion.java:27)
    at SoundApplet.SoundAppletSimpleVersion$12.actionPerformed(SoundAppletSimpleVersion.java:371)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.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.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$000(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

I guess problem is in placing my classes. What I must do to work it correctly? I need Receive MyObject instance into servlet and then work with him in servlet. It works for native Java objects why Java cant find MyObject class in SoundApplet.MyObject.

How Java work with classes in this case. When sending FIle object for example, when I receive it in servlet Java use Which class for it. File Class from libraries in my Applet or File class from libraries in projectwith servlet or it doesnt matter? I am really confused in this questions please try to explain me it and help.

here is image that MyObject class is really placed in compiled SoundApplet.jar in web project..

From The Apache Tomcat 5.5 Servlet/JSP Container: Quick Start:

..

For classes and resources that must be shared across all web applications, place unpacked classes and resources under $CATALINA_BASE/shared/classes, or place JAR files containing those classes and resources under $CATALINA_BASE/shared/lib.

So if SoundApplet.MyObject is in a Jar (which I recommend), place it in the lib directory. If it is not in a Jar, place the class file in the classes/SoundApplet directory. As an aside, package names should be alllowercase, e.g. soundapplet.

Also note that the class needs to be in at least 2 separate locations to be used by both the servlet and applet. The server class-path is outlined above, but applets (or rather the JVM) cannot access either of those paths.