Applet Net Communication
Ok, here's the situation... I have a server application, and I was able to get proper TCP communication going with a test client. Here's the rub: I want to write a client applet.
In the applet, I was able to get the InetAddress of the server by doing a InetAddress.getByName(Hard-coded server IP). Then I try to open a socket using
Socket TCPsocket = new Socket(serverAddress, 2150);
but it hangs on the call.
I'm pretty new to this Applet stuff, though I've written more than a couple of applications for class. Any ideas??
Blake
By default applets only have permission to connect to the server they were downloaded from, i.e. the web-server.
- Marcus
Similar Messages
-
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 -
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, 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,
Danielhi, 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 -
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 javascript communication
hi all,
I want my applet to flash the browser window, came to know that can be done
using applet javascript communication.
ne1 has ne idea how to do that.
thx in adv,
kiran???
-
Applet, Application communication
Hi
Someone tell me how to do applet, application communication.
I have one standalone application, running in server and receiving connection from applets and every min. the server has to send some data back to each apllet connected.
How to do it... any sample or reffernces please..
Thanks in advance
TomyCan you give me example codes using RMI / Socket
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
-
Hello,
I've successfully created a simple client-server application that communicate through the socket,
and now converting to applet, but the following error occured on the java console
java.security.AccessControlException: access denied (java.net.SocketPermission 203.xxx.xxx.xxx:9800 connect,resolve)
that's also the web server where the applet is downloaded
when i try my computer to run the applet (changed the socket ip to 127.0.0.1 or 192.168.0.111 and run the server app) it works just fine..
but when i changed it to the public IP and put it on the webserver that's what happen..
is there any way beside change the policy?
can anyone please help?
I'm really in a big need of help
thank you..
Edited by: bigpappa on Mar 17, 2009 4:05 AM1) There will be no remote server applet. One of the clients will have to run it. Applets are always executed on the client only.
2) For applets communicating with anything else but the server they came from, they need to be signed. -
Applet - FacesServlet communication
I've created and applet that is used to interface with a client's filesystem and comm/serial ports. I would like the applet to be able to send and retrieve data from the server/database. The applet is embedded within a JSF. I'm not sure the correct way to accomplish this. Is there anway to do this within a backing bean? Should I create a phaseListener to handle the intermediary communication between the applet and the database? A servlet filter? Any help or examples would be greatly appreciated.
Thanks,
EricEric,
there is a blog entry: http://www.thoughtsabout.net/blog/archives/000033.html that explains how to access the JSF servlet from a servlet filter, which would give you an option to use this as well. However, I would use this approach only if the Applet needs to be integrated into teh JSF lifecyce - e.g. for event notification. in term of re-usability of the solution Web Services appear the best way to me.
So if you need to e.g. scan a barcode and then update a JSF form with the information and submit it then the blog entry mentioned is the better solution. Otherwise the Webservice does it as well
Frank -
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; -
How to Obtain Applet -servlet communication through https protocol
We are trying to use https protocol.
First I will explain Our Architecture. We are using JRun 3.0
as servlet engine. We are using iplanet as a webserver.
There are two iplanet webservers.
There is a firewall between two iPlanet servers. i.e, one webserver
is outside the firewall. JRun is communicating with inside iplannett
webserver and inside iplannett webserver is communicating with
outside iplannet server.
If we are trying to run the application with
this firewall, our applet is not loading,
but the servlets and jsp pages are all working fine.
Without the firewall, everything is working fine.
The applet is also working fine.
But, with the firewall, our applet is not loading.
We are using JRE 1.3 as java plug-in.
What is the problem so that the applet is not loading.
and How to resolve this? can anybody give suggestion in this regard?
Thanks in advance.No, I am not getting any security exception for the applet, but I am getting the following exception when working with HTTPS. The same application works fine with the default HTTP protocol
java.net.UnknownServiceException: Input from HTTPS not expected until OutputStream is closed
at sun.plugin.protocol.https.BrowserHttpsURLConnection.getInputStream(Unknown Source)
at JBSchedulerXNew.initReceiveAppointmentData(JBSchedulerXNew.java:122)
at JBSchedulerXNew.initReceiveAppointmentData(JBSchedulerXNew.java:92)
at JBSchedulerXNewDemo.init(JBSchedulerXNewDemo.java:110)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source) -
Applet Servlet communication compiles but does not communicate
Hi,
I have a applet which has a button named A. By clicking the button, the applet passes the letter A to the servlet. The servlet in turn accesses an Oracle database and retrieves the name corresponding to letter A from a table (name is Andy in the present case). The servlet interacts with the databse via a simple stored procedure and uses its output parameter to display the name Andy back in the applet.
Both the applet and servlet codes have compiled fine(servlet code compiled with -classpath option to servlet jar using a TOMCAT). However, on clicking button A in the applet, I do not get the name Andy.
Any help/suggestion in resolution of this is highly appreciated. Thanks in advance.
HTML CODE:
<html>
<center>
<applet code = "NameApplet.class" width = "600" height = "400">
</applet>
</center>
</html>
STORED PROCEDURE CODE:
procedure get_letter_description(
ac_letter IN CHAR,
as_letter_description OUT VARCHAR2) IS
BEGIN
SELECT letter_description INTO as_letter_description FROM letter WHERE letter =
ac_letter;
EXCEPTION
WHEN no_data_found THEN as_letter_description := 'No description available';
END get_letter_description;
APPLET CODE:
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.util.*;
import java.io.*;
import java.net.*;
public class NameApplet extends Applet implements ActionListener
private TextField text;
private Button button1;
private String webServerStr = null;
private String hostName = "localhost";
private int port = 8080;
private String servletPath = "/examples/servlet/NameServlet?letter=";
private String letter;
public void init()
button1 = new Button("A");
button1.addActionListener(this);
add(button1);
text = new TextField(20);
add(text);
// get the host name and port of the applet's web server
URL hostURL = getCodeBase();
hostName = hostURL.getHost();
port = hostURL.getPort();
webServerStr = "http://" + hostName + ":" + port + servletPath;
public void actionPerformed(ActionEvent e)
if (e.getSource() == button1)
letter = "" + 'A';
private String getName(String letter){
String name = "" ;
try {
URL u = new URL(webServerStr + letter);
Object content = u.getContent();
name = content.toString();
} catch (Exception e) {
System.err.println("Error in getting name");
return name;
SERVLET CODE:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
import java.util.Properties;
public class NameAppletServlet extends HttpServlet {
private static Connection conn = null;
private static final char DEFAULT_CHAR = 'A';
private static final char MIN_CHAR = 'A';
private static final char MAX_CHAR = 'G';
private static final String PROCEDURE_CALL
= "{call get_letter_description(?, ?)}";
protected void doGet( HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException
handleHttpRequest(request, response);
protected void doPost( HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException
handleHttpRequest(request, response);
protected void handleHttpRequest( HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException
String phrase = null;
char letter = getLetter(request, DEFAULT_CHAR);
if (letter >= MIN_CHAR && letter <= MAX_CHAR) {
try {
name = getName(conn, letter);
} catch (SQLException se) {
String msg = "Unable to retrieve name from database.";
name = msg;
} else {
String msg = "Invalid letter '" + letter + "' requested.";
//throw new ServletException(msg);
phrase = msg;
response.setContentType("text/plain");
PrintWriter out = response.getWriter();
out.println(name);
private String getName(Connection conn, char letter)
throws SQLException
CallableStatement cstmt = conn.prepareCall(PROCEDURE_CALL);
cstmt.setString(1, String.valueOf(letter));
cstmt.registerOutParameter(2, Types.VARCHAR);
cstmt.execute();
String name = cstmt.getString(2);
cstmt.close();
return name;
private char getLetter(HttpServletRequest request, char defaultLetter) {
char letter = defaultLetter;
String letterString = request.getParameter("letter");
if (letterString!=null) {
letter = letterString.charAt(0);
return letter;
public void init(ServletConfig conf) throws ServletException {
super.init(conf);
String dbPropertyFile = getInitParameter("db.property.file");
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection(
"jdbc:oracle:thin:myserver:1521:CDD",
"scott",
"tiger");
} catch (IOException ioe) {
throw new ServletException(
"Unable to init ReinforcementServlet: " + ioe.toString());
} catch (ClassNotFoundException cnfe) {
throw new ServletException(
"Unable to init ReinforcementServlet. Could not find driver: "
+ cnfe.toString());
} catch (SQLException se) {
throw new ServletException(
"Unable to init ReinforcementServlet. Error establishing"
+ " database connection: " + se.toString());
}Hi,
I am not able to understand by which method you are doing Applet-Servlet commuincation.
If you want to use Object Serialization method, plz.get the details from following URL.
http://www.j-nine.com/pubs/applet2servlet/
Ajay -
We currently have an applet for a online submission system for an inhouse form. The applet talks to the server hosting the applet and accesses files from the client computer, so it has a self signed cert. Apperently in a tech company accepting the cirt is too hard, so we need to make the applet run without being signed. That is not a big deal as the file access can go, but I am having a problem with the applet talking to the server. The server just has a java application running, talking on port 1235. When the applet tries to talk back to the server, we get a permision run time error of:
Exception in thread "AWT-EventQueue-2" java.security.AccessControlException: access denied (java.net.SocketPermission graphics1 resolve)
Graphics 1 is the host computer. The url to the html that loads the applet is: Http:\\graphics1\index.html
the content of the html is:
<html>
<head>
<title>Graphics Department E-Request Form </title>
</head>
<br>
<P ALIGN=center>
<applet code="graphicsapp/DCreate"
archive=GraphicsApp.jar,jdnc-0_7-all.jar
width="700"
height="620"
</applet>
<br>
Please contact MIS to upgrade java on your system if you only see a red X
</P>
</html> the applet's network code is:
String Ipaddy="graphics1";
Socket socket = null;
ObjectOutputStream out = null;
ObjectInputStream in = null;
// BufferedReader in = null;
//BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
String serveraddress=Ipaddy;
try {
socket = new Socket(serveraddress, 1235); //it fails here
out = new ObjectOutputStream(socket.getOutputStream());
in=new ObjectInputStream(socket.getInputStream());
//in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out.writeObject(use);It fails if ipaddy is http:\\graphics1
of the actual ip address of the server.
Thanks in advance
Cliffs:
Applet will not connect to originating server without a certGot it, I need to not list the address directly, but instead pull the host from the codebase.
example:
host = getCodeBase().getHost();
try {
address = InetAddress.getByName(host);
} catch (UnknownHostException e) {
System.err.println("Couldn't get Internet address: Unknown host");
// What should we do?
}I got this from
http://java.sun.com/docs/books/tutorial/deployment/applet/examples/QuoteClientApplet.java
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