Thread: mysql in java applets

hello I got this code working fine

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
 
public class connect
{
	public static void main(String[] args)
	{
		Connection conn=null;
		System.out.println("Start.");
		try
		{
			Class.forName("com.mysql.jdbc.Driver");
			System.out.println("So far so good.");
			conn=DriverManager.getConnection("jdbc:mysql://a.b.c.d/db","user","password");
			System.out.println("connected.");
		}
		catch(Exception e)
		{
			e.printStackTrace();
			System.out.println("Bad.");
		}
		finally
		{
			if(conn!=null)
			{
				try
				{
					conn.close();
					System.out.println("close database connection.");
				}
				catch(Exception e){/*ignore this exception*/}
			}
		}
	}
}

but when I put it in an applet like this it stops working for me.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
//import java.sql.*;
 
//import sun.jdbc.odbc.JdbcOdbcDriver
import com.mysql.jdbc.Driver;
 
import java.applet.Applet;
import java.awt.Label;
import java.awt.Button;
import java.awt.TextField;
import java.awt.TextArea;
 
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
 
import javax.swing.JOptionPane;
 
public class guestbook extends Applet
{
        Connection conn=null;
 
	public void init()
	{
		//establich connection
		try
		{
			Class.forName("com.mysql.jdbc.Driver");
			JOptionPane.showMessageDialog(null,"so far so good");
			conn=DriverManager.getConnection("jdbc:mysql://a.b.c.d/db","user","password");
			JOptionPane.showMessageDialog(null,"connected");
		}
		catch(Exception e)
		{
			JOptionPane.showMessageDialog(null,"error");
		}
 
	public void destroy()
	{
		// close database connection
		if(conn!=null)
		{
			try
			{
				conn.close();
			}
			catch(Exception e){/*ignore this exception*/}
		}
	}
}

Originally Posted by copeg

Define 'it stops working'. Does it compile? Are there Exceptions?

In the console program I can connect to the database but not in the applet. I test it on the same computer I program on so I have the CLASSPATH set up, I dont even run a web server (yet), a.b.c.d is my IP-adress.

As Norm said, an applet, by default, would not be able to do this - it doesn't have permission to open a socket to anywhere except for the server where it was served from.

So if the web and mySQL-server is the same computer it should work then?

I realize that you're likely learning so let me push you in the right direction - this is a terrible design. A real system would never, ever, ever allow direct database connections from the outside world. Additionally, your applet would have to contain authorization parameters giving everyone who downloaded the applet the ability to rumage through your database at will.

Again, for a learning exercise this is ok though totally pointless. But if you are ever asked to do the same thing in a professional software environment run, do not walk, to the nearest exit.

I understand the potential hazzard of letting people access a database from the internet but what if the user "user" have read only priviliges on the databade "db" then what is the possible harm if the database is meant to be for public display?

Originally Posted by micro kid

In the console program I can connect to the database but not in the applet. I test it on the same computer I program on so I have the CLASSPATH set up, I dont even run a web server (yet), a.b.c.d is my IP-adress.

I forgot to say that I think have nave narrowed it down to the driver not working when I run the applet which is a mystery to me because the driver works fine for the console program.