Client/server

Question

Hi, i am doing a client/server arc .I have a server , that will connected to the oracle , using jdbc.The client here is an application, how do i change it to applet?
The server code
import java.sql.*;
import java.util.Properties;
import java.io.*;
import java.net.*;
public class CommentsServer extends Thread {
public static final int DEFAULT_PORT = 7777;
protected int port;
protected ServerSocket server;
String username ="combtest";
String password = "combtest";
public static void main (String args[]) {
int port=0;
if (args.length == 1) {
try {
port = Integer.parseInt (args[0]);
} catch (NumberFormatException e) { }
try {
     Class.forName("oracle.jdbc.driver.OracleDriver");
String sourceURL ="jdbc:oracle:thin:@klm:1521:KLMPMIS";
String user="combtest";
String password="combtest";
catch (Exception e) {
System.err.println("Failed to load JDBC driver.");
System.exit (1);
new CommentsServer (port);
public CommentsServer (int port) {
super ("Comments Server");
if (port == 0)
port = DEFAULT_PORT;
this.port = port;
try {
server = new ServerSocket (port);
} catch (IOException e) {
System.err.println ("Error creating server");
System.exit (1);
start();
public void run() {
System.out.println ("Server Running");
ThreadGroup connections = new ThreadGroup ("Comment Connections");
connections.setMaxPriority(this.getPriority()-1);
try {
while (true) {
Socket client = server.accept();
System.out.println ("Connection from: " + client.getInetAddress().getHostName());
CommentsConnection c = new CommentsConnection (connections, client);
} catch (IOException e) {
System.err.println ("Exception listening");
System.exit (1);
System.exit (0);
class CommentsConnection extends Thread {
static int counter = 0;
protected ObjectInputStream in;
protected PrintWriter out;
public CommentsConnection (ThreadGroup group, Socket client) {
super (group, "Connection " + counter++);
try {
in = new ObjectInputStream (client.getInputStream ());
out = new PrintWriter (client.getOutputStream(), true);
} catch (IOException e) {
try {
client.close();
} catch (IOException e2) { }
System.err.println ("Unable to connect.");
return;
start();
public void run () {
try {
String mode = (String)in.readObject();
if (mode.equals("insert")) {
     String name=(String)in.readObject();
try {
     String u="jdbc:oracle:thin:@klm:1521:KLMPMIS";
     Connection con=DriverManager.getConnection(u,"combtest","combtest");
     PreparedStatement prep=con.prepareStatement("Insert into TEST values(?)");
     prep.setString(1,name);
     if(prep.executeUpdate()!=1)
     throw new Exception("Bad update");
} catch (Exception e) {
out.println ("Error updating: " + e);
return;
} else if (mode.equals("query")) {
try {
     Connection con=DriverManager.getConnection("jdbc:oracle:thin:@klmsph1:1521:KLMPMIS","combtest","combtest");
Statement statement=con.createStatement();
ResultSet result=statement.executeQuery("SELECT * FROM TEST");
out.println("Name");
int nameCol=result.findColumn("NAME");
String name,user,comments;
while(result.next())
     name=result.getString(nameCol);
     out.println(name);
statement.close();
con.close();
} catch (Exception e) {
out.println ("Error querying: " + e);
return;
} else {
out.println ("Invalid Command: " + mode);
} catch (Exception e) {
out.println ("Error reading Stream: " + e);
out.close();
the client code
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class CommentsClient extends JApplet{
TextArea ta;
TextField name;     
public static final int DEFAULT_PORT = 7777;
private static final String QueryString = "query";
private static final String InsertString = "insert";
private int port = 0;
private String host = null;
private OutputStream os = null;
public CommentsClient (String host, int port, OutputStream os) {
this.host = host;
this.port = ((port == 0) ? DEFAULT_PORT : port);
this.os = os;
query();
public CommentsClient (String host, int port, OutputStream os,
String name) {
this.host = host;
this.port = ((port == 0) ? DEFAULT_PORT : port);
this.os = os;
insert(name);
private void query () {
PrintWriter out = new PrintWriter (os, true);
try {
Socket s = new Socket (host, port);
ObjectOutputStream oos = new ObjectOutputStream (s.getOutputStream());
// PrintWriter out=new PrintWriter(s.getOutputStream(),true);
oos.writeObject (QueryString);
oos.flush();
BufferedReader in = new BufferedReader (new InputStreamReader (s.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
out.println (line);
out.close();
s.close();
} catch (IOException e) {
out.println ("Error querying." + e);
return;
private void insert (String name) {
PrintWriter out = new PrintWriter (os, true);
try {
Socket s = new Socket (host, port);
ObjectOutputStream oos = new ObjectOutputStream (s.getOutputStream());
oos.writeObject (InsertString);
oos.writeObject (name);
oos.flush();
BufferedReader in = new BufferedReader (new InputStreamReader (s.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
out.println (line);
oos.close();
s.close();
} catch (IOException e) {
out.println ("Error inserting." + e);
return;
public static void main (String args[]) {
if (args.length == 0) {
CommentsClient cc = new CommentsClient ("localhost", 0, System.out);
} else if (args.length == 1) {
CommentsClient cc = new CommentsClient ("localhost", 0, System.out, args[0]);
the applet (acts as an interface)
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.io.*;
//<applet code = "CommentsApplet" width = 800 height = 600>
//</applet>
public class CommentsApplet extends Applet {
TextArea ta;
TextField name;
TextField user;
TextField comments;
public void init () {
Panel p1 = new Panel(new BorderLayout(10, 10));
Button b1 = new Button ("Query");
p1.add (b1, BorderLayout.SOUTH);
ta = new TextArea ();
ta.setEditable(false);
p1.add (ta, BorderLayout.CENTER);
b1.addActionListener (new ActionListener() {
public void actionPerformed (ActionEvent e) {
ByteArrayOutputStream bao = new ByteArrayOutputStream();
CommentsClient cc = new CommentsClient ("localhost", 0, bao);
ta.setText (bao.toString());
add (p1);
Panel p2 = new Panel (new BorderLayout (10, 10));
Button b2 = new Button ("Insert");
p2.add (b2, BorderLayout.SOUTH);
Panel p3 = new Panel();
name = new TextField ("", 10);
p3.add (name);
p2.add (p3, BorderLayout.CENTER);
b2.addActionListener (new ActionListener() {
public void actionPerformed (ActionEvent e) {
ByteArrayOutputStream bao = new ByteArrayOutputStream();
CommentsClient cc = new CommentsClient ("localhost", 0, bao, name.getText());
ta.setText (bao.toString());
add (p2);
the html file
<html>
<body>
<hr>
<applet
code=CommentsApplet.class
width = 400
height = 400
>
</applet>
<hr>
</body>
</html>
Thanks in advance,
Jessy

Answer 1

hi
I have no idea what you are doing. Strange programming
public class CommentsClient extends JApplet why does it extends JApplet when it isn't a JApplet but an application
and why is there a second applet
public class CommentsApplet extends Applet (should this be extends JPanel??)
but for normal classes this is the procedure
rename the constructor in "public void init()" the method init is automaticly called by the browser.
remove the main method if there is some code in the main method that needed move it to the init method. ( in your case the arguments can't be read from the command line but must be read out of the *.html file )