Netscape problem with applet servlet communication

Netscape always seems to get in the way when you use applets, right?
I have a nice set of code from a book that shows how to do applet->servlet stuff.
But although I'm doing this all in the privacy of my own localhost Netscape immediately put a spanner in the works with a security exception and wouldn't let the servlet respond.
Anyone know what to do here.
The answer is to use Internet Explorer, possibly, but I'm in linux, and I can't get Opera to work with java yet.
Anyone got any ideas? Thanks.

I encountered a security exception with Netscape in Linux when attempting applet-servlet stuff but that's prpbably because I haven't got the plugin for that yet...in fact I don't know if a plugin is available for sure...let me know if you do. As a matter of fact I plan on using the HTMLConverter this weekend to find out if it'll download a plugin.
The applet-servlet thing runs fine in IE and Netscape on my Windows box as long as the plugins are there and I use the appropriate plugin tags in the HTML
Post what you find out,
Brad

Similar Messages

Problem with Applet Servlet communication

Hi All,
i am very new to java and servlets......
i am using a applet to call a servlet whose .class file is stored in WEB_INF/classes directory of tomcat..
so what URL address i should use in the new URL( ) constructor ????
presently i have done in this manner..
URL urlServlet = new URL("http://l0.0.2.65:8080/myapp.ServletDB");
URLConnection con = urlServlet.openConnection();
where ServletDB is the name of the servlet .class file
whose address is as follows...
C:\Program Files\Apache Software Foundation\Tomcat 5.5\webapps\myapp\WEB-INF\classes\ServletDB.class
Please help me....
thank you in advance
vijay

Specify Servlet Mapping in web.xml and use that mapped URL
<servlet>
      <servlet-name>getItems</servlet-name>
<servlet-class>myapp.ServletDB</servlet-class>
</servlet>
<servlet-mapping>
      <servlet-name>getItems</servlet-name>
      <url-pattern>/ServletDB</url-pattern>
</servlet-mapping>look at servlet mapping- url-pattern
Now u should use that mapped url while creating URL connection
here is the code.
URL urlServlet = new URL("http://l0.0.2.65:8080/ServletDB");
URLConnection con = urlServlet.openConnection();[Java Servlet tutorials|http://www.jsptube.com]

Need help with applet servlet communication .. not able to get OutputStream

i am facing problem with applet and servlet communication. i need to send few image files from my applet to the servlet to save those images in DB.
i need help with sending image data to my servlet.
below is my sample program which i am trying.
java source code which i am using in my applet ..
public class Test {
    public static void main(String argv[]) {
        try {
                URL serverURL = new URL("http://localhost:8084/uploadApp/TestServlet");
                URLConnection connection = serverURL.openConnection();
                Intermediate value=new Intermediate();
                value.setUserId("user123");
                connection.setDoInput(true);
                connection.setDoOutput(true);
                connection.setUseCaches(false);
                connection.setDefaultUseCaches(false);
                // Specify the content type that we will send binary data
                connection.setRequestProperty ("Content-Type", "application/octet-stream");
                ObjectOutputStream outputStream = new ObjectOutputStream(connection.getOutputStream());
                outputStream.writeObject(value);
                outputStream.flush();
                outputStream.close();
            } catch (MalformedURLException ex) {
                System.out.println(ex.getMessage());
            } catch (IOException ex) {
                    System.out.println(ex.getMessage());
}servlet code here ..
public class TestServlet extends HttpServlet {
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
         System.out.println(" in servlet -----------");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        ObjectInputStream inputFromApplet = null;
        Intermediate aStudent = null;
        BufferedReader inTest = null;
        try {
            // get an input stream from the applet
            inputFromApplet = new ObjectInputStream(request.getInputStream());
            // read the serialized object data from applet
            data = (Intermediate) inputFromApplet.readObject();
            System.out.println("userid in servlet -----------"+ data.getUserId());
            inputFromApplet.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.err.println("WARNING! filename.path JNDI not found");
        } finally {
            out.close();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println(" in foGet -----------");
        processRequest(request, response);
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println(" in doPost -----------");
        processRequest(request, response);
     * Returns a short description of the servlet.
     * @return a String containing servlet description
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}the Intermediate class ..
import java.io.Serializable;
public class Intermediate implements Serializable{
String userId;
    public String getUserId() {
        return userId;
    public void setUserId(String userId) {
        this.userId = userId;
}

Hi,
well i am not able to get any value from connection.getOutputStream() and i doubt my applet is not able to hit the servlet. could you review my code and tell me if it has some bug somewhere. and more over i want to know how to send multiple file data from applet to servlet . i want some sample or example if possible.
do share if you have any experience of this sort..
Thanks.

Problem in Applet Servlet communication in cluster

          Our new production server has been configured with
          clusters very recently.The application is running fine if and only if one instance
          of weblogic is running.The application has two applets that communicate through a
          servlet and the servlet is hosted by both the WL servers in the cluster.
          Please consider the following scenario :
          1. JSP#1(having embedded tag for Applet#1) is served by, say, WLInstance#1.
          2. JSP#2(having embedded tag for Applet#2) is served by, say, WLInstance#2.
          3. Applet#1 is loaded by BrowserInstance#1.
          4. Applet#2 is loaded by BrowserInstance#2.
          The way I understand applet-servlet communication is as follows :
          The servlets are invoked through the url-pattern specified in web.xml - if the applet
          is making use of a certain url-pattern that is mapped to servlet, then the call from
          that applet will
          eventually invoke a servlet on any of the two instances till a session is established,
          at which point all subsequent requests from the same browser window/frame will go
          to the servlet hosted on the instance where the http session was created.
          (Please correct me, if I am wrong.)
          So, Applet#1 will always talk to the servlet hosted by WLInstance#1 and Applet#2
          will always talk to the servlet hosted by WLInstance#2.
          In our case, the servlet is maintaining data structures to store all the messages
          sent by diffterent instances of Applets.
          The applets periodically polls the messages from those data structures.Once the messages
          are polled, those are deleted from
          the data structures.
          As there are two different instances of the servlet, Applet#1 never gets messages
          posted by Applet#2.
          Is there a way to make this data structure global to both the servlet instances?
          Thanks and best regards,
          Subir Das


          "Subir Das" <[email protected]> wrote:
          >So, Applet#1 will always talk to the servlet hosted by WLInstance#1 and
          >Applet#2
          >will always talk to the servlet hosted by WLInstance#2.
          This statement is not entirely true.
          Suppose WLInstance#1 were to be brought down (for whatever reason), Applet#1 will
          then talk to servlet hosted by WLInstance#2.
          Server pinning could be modified by different load balancing algorithms, configurable
          via containers (or hardware).
          So don't count on which servlet instance your applet is going to be served by.
          Instead consider to give a second look into the design of the servlet data structure
          (object):
          1.Read from data store, if it has been persisted.
          2.If the data is client related then consider sticking the data into session, which
          would then replicate to other WL instances.
          3.Stateless EJB in a cluster ? Don' know much about this(yet).
          My 2 cents..Good luck.
          Rama

Big Problem in Applet-Servlet Communication-(Help)

I wrote an method to send serialized objects from Applet to Servlet,
the method is as following:
private ObjectInputStream postObjects (URL servlet, Serializable objs[], String sessionID) throws Exception {
ObjectInputStream in = null;
ObjectOutputStream out = null;
try{
URLConnection con = servlet.openConnection();
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches(false);
con.setRequestProperty("Content-Type","application/x-java-serialized-object");
con.setAllowUserInteraction(false);
con.setRequestProperty("Cookie", sessionID);
out = new ObjectOutputStream(con.getOutputStream());
int numObjects = objs.length;
for(int x = 0; x < numObjects; x++){
out.writeObject(objs[x]);
out.flush();
out.close();
in = new ObjectInputStream(con.getInputStream());
}catch(Exception e){
e.printStackTrace(System.err);
throw e;
}finally{
return in;
when I call this method, I got the following error message in Applet console,
my platform is Salaris 5.8 + iPlanet 6.0.
java.io.EOFException
     at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2150)
     at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2619)
     at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:726)
     at java.io.ObjectInputStream.<init>(ObjectInputStream.java:251)
     at com.shinewave.lms.core.client.ServletProxy.postObjects(ServletProxy.java:255)
     at com.shinewave.lms.core.client.ServletProxy.doInitialize(ServletProxy.java:76)
     at com.shinewave.lms.core.client.APIAdapterApplet.LMSInitialize(APIAdapterApplet.java:60)
java.lang.NullPointerException
     at com.shinewave.lms.core.client.ServletProxy.doInitialize(ServletProxy.java:77)
     at com.shinewave.lms.core.client.APIAdapterApplet.LMSInitialize(APIAdapterApplet.java:60)
java.lang.NullPointerException
     at com.shinewave.lms.core.client.ServletProxy.doInitialize(ServletProxy.java:82)
     at com.shinewave.lms.core.client.APIAdapterApplet.LMSInitialize(APIAdapterApplet.java:60)
Please help me to solve this problem, thank you very much.

Hi..
Sorry abt this. But I was hoping if u could help out on this..
I am trying to implement a applet to servlet communication...
wherin the servlet would read data from the database... and send it back to the applet which gets displayed on the applet...
But the problem is that the applet is not able to establish a connection with the servlet..
I am also using another supportive class whose object is basically passed from the servlet to the applet..
could u help me..
below is the piece of code...
APPLET:
import java.net.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
public class TestApplet extends JApplet implements ActionListener
     JButton btnLoad;
     JTextField tfEmpno, tfFname, tfLname, tfSalary;
     URL url;
private String webServerStr = null;
private String hostName = "sandy";
private int port = 8085;
private String servletPath = "/jdbcTest.DBDetailsServlet";
public TestApplet()
     super();
// suppress Warning Message
getRootPane().putClientProperty"defeatSystemEventQueueCheck",Boolean.TRUE);
     public void actionPerformed(ActionEvent ae)
          if(btnLoad.getText().equals("Load"))
               if(loadData())
                    btnLoad.setText("Save");
          else
               btnLoad.setText("Load");
//               saveData();
     public void init()
          setBackground(Color.pink);
          tfEmpno = new JTextField(10);
          tfFname = new JTextField(10);
          tfLname = new JTextField(10);
          tfSalary= new JTextField(10);
          JPanel panel = new JPanel();
          panel.setLayout(new FlowLayout());
          panel.add(tfEmpno);
          panel.add(tfFname);
          panel.add(tfLname);
          panel.add(tfSalary);
          getContentPane().add(panel, BorderLayout.CENTER);
          JPanel bottom = new JPanel(new FlowLayout());
          btnLoad = new JButton("Load");
          btnLoad.addActionListener(this);
          bottom.add(btnLoad);
          getContentPane().add(bottom, BorderLayout.SOUTH);
     public boolean loadData()
          try
     System.out.println("Web Server host name: " + hostName);
     webServerStr = "http://" + hostName + ":" + port + servletPath;
     System.out.println("Web String full = " + webServerStr);
               String servletGET = webServerStr + "?"
     + URLEncoder.encode("UserOption") + "="
     + URLEncoder.encode("AppletDisplay");
//               url = new URL(getCodeBase(),"http://sandy:8080/servlet/jdbcTest.DBDetailsServlet");
               System.out.println("Complete Servlet Url => " + servletGET);
               url = new URL(servletGET);
               URLConnection con = url.openConnection();
               con.setUseCaches(false); // Turn off caching.
               InputStream in = con.getInputStream();
               System.out.println("\nsuccess ....... con.getInputStream() ");
               ObjectInputStream ois = new ObjectInputStream(in);
               System.out.println("\nsuccess ....... new ObjectInputStream(in) ");
               Object object = ois.readObject();
               System.out.println("\nGot the object from servlet...");
               if(object != null)
                    System.out.println("\nObject NOT null ...");
                    ArrayList result = (ArrayList) object;
                    jdbcTest.EmployeeValue empval = (jdbcTest.EmployeeValue) result.get(0);
                    tfEmpno.setText(""+empval.getEmp_no());
                    tfFname.setText(empval.getFname());
                    tfLname.setText(empval.getLname());
                    tfSalary.setText(""+empval.getSalary());
                    System.out.println("\nObject processed " + result);
                    repaint();
               return true;
          catch(Exception e)
               e.printStackTrace();
               System.out.println("\n\n loadData()=> E X C E P T I O N : " + e + "\n");
               return false;
     public void saveData()
          //yet to be implemented..
SERVLEt:
package jdbcTest;
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class DBDetailsServlet extends HttpServlet
     public void doGet(HttpServletRequest req,HttpServletResponse res )throws ServletException, IOException
          System.out.println("\nInside the doGet()\n");
          ArrayList results = getDetails();
          ObjectOutputStream oos = new ObjectOutputStream(res.getOutputStream());
          oos.writeObject(results);
     public void doPost(HttpServletRequest req,HttpServletResponse res )throws ServletException, IOException
          System.out.println("\nInside the doPost()\n");
          doGet(req,res);
     public ArrayList getDetails()
          try
               System.out.println("\nServlet : inside GetDetails...");
               Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
               java.sql.Connection con = java.sql.DriverManager.getConnection("jdbc:odbc:SandyDSN","","");
               java.sql.Statement stmt = con.createStatement();
               System.out.println("\n Statement created..");
               java.sql.ResultSet rs = stmt.executeQuery("SELECT * FROM EMP WHERE EMP_NO = 222");
               System.out.println("\n Query Executed...");
               ArrayList results = new ArrayList();
               while(rs.next())
                    EmployeeValue empval = new EmployeeValue();
                    empval.setEmp_no(rs.getLong("EMP_NO"));
                    empval.setFname(rs.getString("FNAME"));
                    empval.setLname(rs.getString("LNAME"));
                    empval.setSalary(rs.getLong("SALARY"));
                    results.add(empval);
               System.out.println("\n Resultset Obtained...");
               stmt.close();
               con.close();
               return results;
          catch(Exception e)
               System.out.println("Error while retreiving details....." + e);
               return null;
     public boolean saveDetails(EmployeeValue empval)
          try
               return true;
          catch(Exception e)
               System.out.println("Error while updating details....." + e);
               return false;
The utility class EMployeeValue is as below:
package jdbcTest;
import java.io.*;
class EmployeeValue implements Serializable
     private long emp_no;
     private String fname;
     private String lname;
     private long salary;
     public EmployeeValue()
          super();
     public EmployeeValue(long eno, String fn, String ln,long sal)
          super();
          setEmp_no(eno);
          setFname(fn);
          setLname(ln);
          setSalary(sal);
     public long getEmp_no()
          return emp_no;
     public java.lang.String getFname()
          return fname;
     public java.lang.String getLname()
          return lname;
     public long getSalary()
          return salary;
     public void setEmp_no(long newEmp_no)
          emp_no = newEmp_no;
     public void setFname(java.lang.String newFname)
          fname = newFname;
     public void setLname(java.lang.String newLname)
          lname = newLname;
     public void setSalary(long newSalary)
          salary = newSalary;

Security problems while applet servlet communication

hi,
iam using sun server for my application..iam calling an applet in a jsp page..when this applet loads it displays values which r retreived from other server using servlets..in applet init method iam calling a method called getDocClassDesc which is in applettoservet.java..in this method i will pass parameters to a servlet called interaction servlet..in servlet i will retreive parameter and call a bean method for getting docclassdesc..my problem is when i load this in browser it is not loading applet.and not showing anything..at the bottom of browser status bar showing that search applet not inited...
what could be the problem..is it of permission policy of settings..if so i do set these things in sun server..give me the code also..
if not any other problem plz give me hints..
if i just display normal aplet without retreiving from servlet it is working fine..but when communicaion with servlet and retreivel then nothing..plz help me..
regards,
sam

Trace would help maybe:
To turn the full trace on (windows) you can start the java console, to be found here:
C:\Program Files\Java\j2re1.4...\bin\jpicpl32.exe
In the advanced tab you can fill in something for runtime parameters fill in this:
-Djavaplugin.trace=true -Djavaplugin.trace.option=basic|net|security|ext|liveconnect
if you cannot start the java console check here:
C:\Documents and Settings\userName\Application Data\Sun\Java\Deployment\deployment.properties
add or change the following line:
javaplugin.jre.params=-Djavaplugin.trace\=true -Djavaplugin.trace.option\=basic|net|security|ext|liveconnect
The trace is here:
C:\Documents and Settings\your user\Application Data\Sun\Java\Deployment\log\plugin...log

JRE/JDK Problem with Applet/Servlet scenario

Hi there!
I'am forced by my company to upgrade an old Java application. The situation is, that an signed applet calls several servlets (running on Tomcat 4.x or 5.x) over http(s).
In former times both, servlet container and applet, were using jre 1.4.1.x
(The servlet container was ServletExec, so a jre was sufficient).
Everything was working fine, if the client was using the 1.4.1 jre.
But on later versions (1.4.2.x) the whole Applet-jar was downloaded from the server per user interaction, whats definitly not acceptable as customers still using isdn or nowadays umts.
Any sugesstions?
Thanks
Buzz

Double Posted:
http://forum.java.sun.com/thread.jsp?thread=553517&forum=33&message=2709389
And the answer is the same. You will have to open multiple connections. One for each time want to send data to the Servlet, because that is how HTTP works.
Try a simple case, where you want to send a single object through to the Servlet, then read the response.
When that works, repeat it for every subsequent time you want to send or recieve data.
If you want to have continuous communication between the server and the client, you do not want to use HTTP.

HttpURLConection.getInputStream() problem in applet/servlet communication

I have set property con.setRequestProperty("Content-type",
"application/octet-stream");
in java applet that is supposed to communicate with servlet
Also I have set resp.setContentType("application/octet-stream");
in servlets Service method,
But when I try ro getinput stream back in applet It gives an 405 error on DOS Prompt at this line
DataInputStream in =new DataInputStream(con.getInputStream());
On debugging I found from con.getContentType() just before this
line that it returns text/html;charset=ISO-8859-1 (which i suppose
should be application/octec-stream)
I don't have any more clues please help.

search the forum........

Applet-servlet communication, object serialization, problem

hi,
I encountered a problem with tomcat 5.5. Grazing the whole web i didn't find any solution (some guys are having the same problem but they also got no useful hint up to now). The problem is as follows:
I try to build an applet-servlet communication using serialized objects. In my test scenario i write a serialized standard java object (e.g. a String object) onto the ObjectOutputStream of the applet/test-application (it doesn't matters wheter to use the first or the latter one for test cases) and the doPost method of the servlet reads the object from the ObjectInputStream. That works fine. But if i use customized objects (which should also work fine) the same code produces an classnotfound exception. When i try to read and cast the object:
TestMessage e = (TestMessage)objin.readObject();
java.lang.ClassNotFoundException: TestMessage
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1359)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
...That seems strange to me, because if i instantiate an object of the same customized class (TestMessage) in the servlet code, the webappclassloader doesn't have any problems loading and handling the class and the code works fine!
The class is located in the web-inf/classes directory of the application. I've already tried to put the class (with and without the package structure) into the common/classes and server/classes directory, but the exception stays the same (I've also tried to build a jar and put it in the appropriate lib directories).
I've also tried to catch a Throwable object in order to get information on the cause. But i get a "null" value (the docu says, that this will may be caused by an unknown error).
I've also inspected the log files intensively. But they gave me no hint. Until now I've spend a lot of time on searching and messing around but i always get this classnotfound exception.
I hope this is the right place to post this problem and i hope that there is anyone out there who can give me some hint on solving this problem.
Kindly regards,
Daniel

hi, thanks for the reply,
all my classes are in the web-inf/classes of the web-app and have an appropriate package structure. thus the TestMessage class is inside a package.
i tried some names for the testclass but it didn't matter. the exception stays the same. I also tried to put the jar in the common/lib but the problem stays.
Well the problem with loaded classes: As i mentioned in the post above i can instantiate an object of TestMessage in the code without any problems (so the classloader of my webapp should know the class!!)
only when reading from the objectinputstream the classloader doesn't seem to know the class?? maybe theres a parent classloader resposible for that and doesn't know the class?
strange behaviour...
p.s. sending the same object from the servlet to the client works well
regards
daniel
Message was edited by:
theazazel

Problem in Applet while communicating with Javascript

Hi,
Im facing a problem with applet. Applet calls JavaScript methods and vice versa. Applet works fine with JRE 5 to JRE 6 up to build no 1.6.0._7 but it fails with build no 1.6.0_10.
The problem description is given below:
After embedding applet in my HTML page using <OBJECT> tag, Ive to check either any problem during applets execution, I want to get the error reason by calling my defined method getErrorReason() in applet that returns the error reason, I call the getErrorReason() against the applets object in JavaScript immediately after embed applet code in my HTML page, a JavaScript errors occurs and my applet fails to perform its execution.
JavaScript error: Object does not support this property.
The error points to the HTML page area where Im calling getErrorReason() against applet object.
The above JavaScript error occurs after the successful completion of Applets init(). Im facing this problem only in JRE 6 build 1.6.0_10-b33.
Please suggest me any solution.
Thanks in advance.
Regards,
Israr Ahmed

Hi Bharath,
Even i got similar error and i tried deleting the below(Attaching the stack trace is always better way.)
1) delete the folder workspace or rename(including all files and subfolders) in the path D:\Documents and Settings\lzcr8r\Documents\SAP\workspace
2) delete all .dtr/.dtc/.metadata directories in your personal folder (e.g. C:\Documents and Settings\lzcr8r).
Restart the IDE once you are done with the above steps.
Second part to increase the virtual mem
1) RtClick on the Shortcut of NWDS -->Properties and in the Target put the below
"C:\Program Files\SAP\IDE\IDE70\eclipse\SapIde.exe" -vmargs -Xms512m -Xmx1536m "C:\j2sdk1.4.2_08\bin\javaw.exe"
2) You can also try Creating a bat file with the complete path of your IDE and start your ide from the bat
content in the bat eg: "C:\Program Files\netbeans-4.1\bin\netbeans.exe" -vmargs -Xms512m -Xmx1536m
Here -Xms512m is the min JVM size and -Xmx1024m is the max JVM size.
You can place this batch file anywhere and double click the batch file.
It will automatically start your IDE
3) if you are using Tomcat you can try creating an env variable and assign Value
Variable Name: CATALINA_OPTS
Variable Value: -server -Xmx800m
please award points if usefull.
Regards
Souza
Edited by: Souza Aluri on Apr 9, 2008 9:46 AM

Asynchronous applet-servlet communication

Hi all,
I am trying to implement asynchronous applet-servlet communication and need your help. Anything would help(I tried with synchronous applet-servlet communication but doesn't solve my problem).
Thanks,

http://java.sun.com/docs/books/tutorial/networking/index.html
You can open a socket connection. Bother the client and the server
can have separate threads for reading and writing and that you gives you
asynchronous communication. Later, if you think the server is generating
too many threads and not scaling, you can use features of .java.nio to
make it more scalable:
java.nio.channels

Is there a good advanced review on applet-servlet communication

I am working on a web application and unfortunately experiencing a lot of trouble trying to use an applet as front end which interacts with a couple of servlets running on Tomcat. I need to get data from one servlet and send data to another.
There is a lot of messages posted in this and other forums about how to do this, but none of them got a response pointing to a useful advanced reference on this subject. I have reviewed some of the references given, but couldn't find a thorough detailed advanced reference on applet-servlet communication. For this I mean an exhaustive explanation of the mechanism of communication and when and when is neccesary to use each of the multiple configuration possibilities regarding content-type, message-length, request-method, connection settings, and so on.
Would anybody be so kind to show me the right direction? As I read the (literally) hundreds of messages posted on this topic, I see this info as widely useful. Most of the topic tracks ends on void or with painful no-way sentences, and maybe many people is avoiding Java technology on web application because of this problem (development delays can abort a project).

This sample chapter in Java developers' guide to Servlets and Jsp focuses on Applet-Servlet communication, is a pretty good one, and is free :
http://www.javaranch.com/bunkhouse/samps/2809ch12.pdf
As to an exhaustive & complete guide that covers absolutely everything, I may be wrong but I doubt you'll find anything like that...unless there is a book somewhere dedicated to the subject.

Applet/Servlet communication - StreamCorruptedException

Hi, I'm having a problem when I try to connect to a servlet. I am using applet/servlet communication. The problem only occurs when I have lauched a crystal report via http in a new window.
After the report is launched if I try to hit my servlet I get the following error:
java.io.CorruptedStreamException: invalid stream header
Not all crystal reports I launch cause this behavior but I can see nothing in the url I use to launch the report that is out of place or different than other reports.
APPLET-SERVLET CONNECTION
try {
StringBuffer path = new StringBuffer();
path.append(ip);
path.append("servlet/DatabaseServlet?");
path.append("option=getRecords&query=").append(URLEncoder.encode(query,"UTF-8"));
URL url = new URL(path.toString());
URLConnection servletConnection = url.openConnection();
servletConnection.setUseCaches(false);
servletConnection.setDoInput(true);
servletConnection.setDoOutput(true);
servletConnection.setRequestProperty("Content-Type", "application/x-java-serialized-object");
ObjectInputStream inputFromServlet = new ObjectInputStream(servletConnection.getInputStream());
rc = (RecordCollection) inputFromServlet.readObject();
inputFromServlet.close();
} catch (Exception e) {
e.printStackTrace();
SERVLET CODE
Forwards to doPost
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("session id: " + request.getSession().getId());
this.doPost(request, response);
LAUNCHING REPORT FROM APPLET
try {
String launchURL = host + directory + report + "?promptOnRefresh=0"+ "&" +
authentication + "&" + key + "&" + startPeriods + "&" + reportYears + "&" + reportTitle + "&" endPeriods "&" + locations + "&" + reportPeriod + "&" + fiscalWeek + "&" + fiscalYear + "&" +time;
context.showDocument(new URL(launchURL), "_blank");
} catch (Exception ex) {
ex.printStackTrace();
SAMPLE URL THAT CAUSES PROBLEM
http://localhost:113/Reports/OpenToBuy_3.class?promptOnRefresh=0&user0=rpuser&password0=er34sw1&[email protected]=rpuser&[email protected]=er34sw1&user0@sub2=rpuser&[email protected]=er34sw1&promptex-key="L","L1","ALL"&promptex-start="1"&promptex-years="2004","2004"&promptex-title="Report Title"&promptex-end="1"&promptex-locs="01","03","04","05"&promptex-period="Feb 2004 [04-01]"&promptex-cw="1"&promptex-cy="2004"&promptex-time=-2-52728"
Everything works fine until I launch this report then I can no longer get data from my servlet. I thought the URL lenght for the report might be the problem but I lauch a report with a URL longer than the problem one and there I don't get the errors after. When I try to connect to the servlet the println statement in the doGet method of my servlet doesn't get printed so it's not even making it inside that method in the servlet.
Anyone have any idea what could be causing this? Anyone have any ideas what would be causing this? I'm really stumped.

I've seen this problem before. Because your accessing a complete URL (ie http://<host>:<port>/xxx), you are actually creating a new session. Whenever the applet opens a connection to a servlet it is running on it's own session not the same as the JSP. This is rather obvious since the Page and Applet are separate entities.
Try sending authentication with the url. I think the syntax is:
username:password@http://localhost/xxx
However I'm not sure how well this might work for Tomcat. As for Java it may try and throw a MalformedURLException I would have to test it first - it's been a long time since I used this technique!
Wish I could be more help,
Anthony

Applet/servlet communication for byte transmission

Hello all !
I wrote an applet to transfer binary file from web servlet (running under Tomcat 5.5) to a client (it's a signed applet) but I have a problem of interpretation of byte during transmission.
the code of the servlet is :
        response.setContentType("application/octet-stream");
        ServletOutputStream sos = response.getOutputStream();
        FileInputStream fis = new FileInputStream(new File(
                "C:\\WINDOWS\\system32\\setup.bmp"));
        byte[] b = new byte[1024];
        int nbRead = 1;
        while (nbRead > 0) {
            nbRead = fis.read(b);
            System.out.println("octets lus = " + nbRead);
            sos.write(b, 0, nbRead-1);
        fis.close();
        sos.close();et le code de l'applet qui appelle cette servlet est :
        URL selicPortal = null;
        try {
            selicPortal = new URL(
                    "http://localhost:8080/AppletTest/servlet/FileManipulation");
        } catch (MalformedURLException e) {
            e.printStackTrace();
        URLConnection selicConnection = null;
        try {
            selicConnection = selicPortal.openConnection();
        } catch (IOException e) {
            e.printStackTrace();
        selicConnection.setDoInput(true);
        selicConnection.setDoOutput(true);
        selicConnection.setUseCaches(false);
        selicConnection.setRequestProperty("Content-Type",
                "application/octet-stream");
        try {
            InputStream in = selicConnection.getInputStream();
            FileOutputStream fos = new FileOutputStream(new File(tempDir
                    + "\\toto.bmp"));
            byte[] b = new byte[1024];
            int nbRead = in.read(b);
            while (nbRead > 0) {
                fos.write(b);
            in.close();
            fos.close();
         } catch (IOException ioe) {
            ioe.printStackTrace();
        }the file dowloaded is broken. it seems that bytes 01 00 or 00 01 are not correctly process.
Some ideas to help me please ?

hi,
have you solved this issue.. please post me the code since i m also doing the applet/servlet communication and can use your code as reference.
how to read the content placed in the urlConnection stream in the servlet
Below is my code in applet
public void upload(byte[] imageByte)
          URL uploadURL=null;
          try
               uploadURL=new URL("<url>");
               URLConnection urlConnection=uploadURL.openConnection();
               urlConnection.setDoInput(true);
               urlConnection.setDoOutput(true);
               urlConnection.setUseCaches(false);
               urlConnection.setRequestProperty("Content-type","application/octet-stream");
               urlConnection.setRequestProperty("Content-length",""+imageByte.length);
               OutputStream outStream=urlConnection.getOutputStream();
               outStream.write(imageByte);
               outStream.close();
          catch(MalformedURLException ex)
          catch(IOException ex)
How can i read the byte sent on the outstream (in above code) in the servlet.
Thanks,
Mclaren

Problems with MSA - IPC communication

Hello.
We experience some problems with MSA -> IPC communication on our Mobile Clients.
The version of CRM is 7.0.
The problem seems to be related to mobile clients switching status (online | offline | vpn connected | disconnected | etc).
It is difficult to predict the behaviour of a general salesperson, but regardless when the mobile client is awaken and MSA is already running, the connection to the IPC should work, right ?
I wonder if anyone else has experienced any problems related to this ?
Our platform is Windows 7, we use Checkpoint vpn-client.
From what i've seen during testing, the problem is not consistent, it arises at odd times but it seems to be related to Network/VPN connection.
What we have done is edit the tomcat\conf\server.xml file to bind tomcat to localhost address: 127.0.0.1. I've not been able to reproduce the problem when binding tomcat to this address. However, i would really appreciate any feedback on this matter.
BR Gerhard.

Does the user has Admin rights for the laptop ?
Rgds,
Shobhit

Netscape problem with applet servlet communication

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