Applet connection with a servlet.

Question

hi all.
i need to send data from an applet in the client side to a servlet on the server.
i want to send this data via http so i won't have to get around firewalls and other problems that might come up if i'll use sockets.
i'm sending objects, like this: (applet side)URL url = new URL("http://localhost:8080/examples/servlet/ImportListener.Listener");
URLConnection con = url.openConnection();
con.setUseCaches(false);
OutputStream out = con.getOutputStream();
ObjectOutputStream objStream = new ObjectOutputStream(out);
objStream.writeObject(record);i have two questions:
(1) how do i get this object data in the servlet??? will it be in the doGet() method?
(2) how can i send a confirm message back to the applet?
thanks!

Answer 1

Hi!
I have implemented such case, and I thought it might be so helpful for all to post the solution over here, I will provide two cases in one example, first, the applet will send parameters within the posted URL, and in this case you can retrieve them in doGet method, another case is to write objects over output streams, and in this case it will be sent to the servlet using POST method, because the GET method does not have a body which must be exist to handle the streams, so, the whole request will be sent over POST method, and to get it, fill up your Java doPost():
NOTE: Any object you want to send/retrieve over a network MUST be serializable, which means, the class must implement java.io.Serializable.
The Applet - CLIENT
================
public boolean getSomeInformation(Object myObject)  {
        // Get a backend connection, see the connect() method below
        URLConnection connection = connect("/myAliasServlet?myname=nabieh&myage=28");
        BufferedReader servletResponse = null;
        ObjectOutputStream oos = null;
        try {
            oos = new ObjectOutputStream(connection.getOutputStream());
            // serialize the object
            oos.writeObject(myObject);
            oos.flush();
            // Read the response from the servlet:
            servletResponse = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String response;
            String s = "";
            while (null != ((response = servletResponse.readLine()))) {
                s += response;
            if (s != null) {
                if (s.equals("SUCCESS")) {
                    executed = true;
                } else {
                     // s = "null"!
                    JOptionPane.showMessageDialog(myForm, s, "Error", JOptionPane.ERROR_MESSAGE);
                    executed = false;
        } catch (IOException ioe) {
            ioe.printStackTrace();
        } finally {
            try {
                if (oos != null) {
                    oos.close();
                if (servletResponse != null) {
                    servletResponse.close();
            } catch (IOException ioe) {
                ioe.printStackTrace();
        return executed;
public URLConnection connect(String alias) {
        URLConnection connection = null;
        String serverContext = "http://192.168.0.2:8888/MyApp";
        // Connecting to the server:
        try {
            String s = serverContext + alias;
            URL url = new URL(s);
            connection = url.openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setUseCaches(false);
            connection.setRequestProperty("Content-Type", "application/octet-stream");
        } catch (MalformedURLException murle) {
            murle.printStackTrace();
        } catch (IOException ioe) {
            ioe.printStackTrace();
        return connection;
    }The servlet, server side:
===================
Here, the servlet reads the object, do some process whatever it is, pass back a String to the client, the applet.
protected void doPost(HttpServletRequest request,
               HttpServletResponse response) throws ServletException, IOException {
                // Get both passed parameters, myname and myage
                 String name = request.getParameter("myname");
          String age = request.getParameter("myage");
               // Get the seializable object
          ObjectInputStream ois = new ObjectInputStream(request.getInputStream());
          MyObject mo = null;
          try {
               mo = (MyObject ) ois.readObject();
          } catch (IOException ioe) {
               System.out.println(ioe.getMessage());
          } catch (ClassNotFoundException cnfe) {
               System.out.println(cnfe.getMessage());
          // Do whatever you want over here...
                String found = doSomeThing(mo); // This method gonna return a string, "SUCCESS" or "null".
                PrintWriter pw = response.getWriter();
          pw.write(found);
          pw.flush();
          pw.close();
     }Good luck.