Topic: Communication between Servlet and Applet

====== Applet ======
 
public class HelloWorldApplet extends Applet
{
    JPanel panel = null;
    JLabel label = null;
 
    public void init()
    {
        try {
            panel = new JPanel();
 
            panel.setLayout(new GridLayout(1,2));
            label = new JLabel("first file modified");
            label.setBackground(new Color(153, 184, 213, 100));
            panel.add(label);
 
            JComponent data = (JComponent)sendObject();
 
            //JButton button = new JButton(data);
            add(data);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    public Object sendObject() {
        OutputStream out;
        ObjectOutputStream objectStream;
        Object data = null;
        try {
            URLConnection con = getServletConnection();
            out = con.getOutputStream();
            objectStream = new ObjectOutputStream(out);
            objectStream.writeObject("request from applet");
            objectStream.flush();
            objectStream.close();
 
            out.close();
 
            data = readInputStream(con);
 
        } catch(Exception e) {
            e.printStackTrace();
        }
        return data;
    }
 
    private URLConnection getServletConnection() throws MalformedURLException, IOException  {
        URL servletURL = new URL("http://10.77.5.192:8080/plugins/servlet/helloworld");
        URLConnection con = servletURL.openConnection();
        con.setDoInput(true);
        con.setDoOutput(true);
        con.setUseCaches(false);
        con.setDefaultUseCaches(false);
        ((HttpURLConnection) con).setRequestMethod("POST");
        con.setRequestProperty("Content-Type","application/x-java-serialized-object");
        con.setAllowUserInteraction(false);
        return con;
    }
 
    private Object readInputStream(URLConnection con) {
        Object object = null;
 
        try {
            InputStream in = con.getInputStream();
            ObjectInputStream objectInputStream = new ObjectInputStream(in);
            object = objectInputStream.readObject();
            in.close();
        } catch(Exception e) {
            /*try {
                    // now failing to read the inputstream does not mean the server did not send
                    // any data, here is how you can read that data, this is needed for the same
                    // reason mentioned above.
                    ((HttpURLConnection) con).getResponseCode();
                    InputStream es = ((HttpURLConnection) con).getErrorStream();
                    int ret = 0;
                    // read the response body
                    while ((ret = es.read(byteBuffer)) > 0) {
                    }
                    // close the errorstream
                    es.close();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }*/
                e.printStackTrace();
        }
 
        return object;
    }
}
 
====== Servlet ======
 
public class HelloWorldServlet extends HttpServlet {
 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        ObjectInputStream in = null;
 
        try {
            ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
            InputStream inStream = request.getInputStream();
            byte byteBuffer[] = new byte[1024];
            int len;
 
            while((len = inStream.read(byteBuffer)) > 0) {
                byteStream.write(byteBuffer);
            }
 
            in = new ObjectInputStream(new ByteArrayInputStream(byteStream.toByteArray()));
            Object obj = in.readObject();
 
            response.setContentType("application/x-java-serialized-object");
            OutputStream outStream = response.getOutputStream();
            ObjectOutputStream objectStream = new ObjectOutputStream(outStream);
            objectStream.writeObject(new DiffPanel());
            objectStream.flush();
            objectStream.close();
 
            //outStream.close();
            in.close();
            byteStream.reset();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

另一个例子：

Servlet:

// ObjectInputStream inputStream = new ObjectInputStream(
// new BufferedInputStream(request.getInputStream()));
//
// try {
// System.out.println("got this:");
//
// System.out.println("got this1-->" +
// inputStream.readObject().toString());
// System.out.println("got this2-->" +
// inputStream.readObject().toString());
//
// } catch (Exception ex) {
// System.out.println("error: " + ex);
// } finally {
// try{
// inputStream.close();
// } catch (Exception e1){
// // Do nothing
// }
// System.out.println("-end-");
// }

Applet:

// ObjectInputStream response = null;
// Object result = null;
//
// try {
//
// System.out.println("Start");
//
//
// URL url = new URL(getCodeBase(), "/psmis/pmMeterImport.html");
//
// System.out.println(url.toExternalForm());
//
// URLConnection urlConnection = url.openConnection();
// urlConnection.setDoOutput(true);
// urlConnection.setUseCaches(false);
// urlConnection.setRequestProperty("Content-Type",
// "application/octet-stream");
//
// ObjectOutputStream request = new ObjectOutputStream(
// new BufferedOutputStream(urlConnection.getOutputStream()));
// request.writeObject("Test Object");
// request.writeObject(new Point(3,5));
// request.flush();
// request.close();
//
//
// InputStream is = urlConnection.getInputStream();
//
// System.out.println("finished");
// } catch (Exception ex){
// System.out.println("error");
// ex.printStackTrace();
// } finally {
// try {
// if(response != null) {
// response.close();
// }
// } catch (Exception ex) {
// // Do nothing
// }
// }