Problems connecting to mysql database on network

Hi there,

I'm currently teaching myself Java from a for dummies book. However I have currently got stuck on the section to connect to a mysql database, in the book it assumes that the database is on a local machine however in my case it is on my server. Both machines are running Linux and my workstation has mysql-jdbc installed on it.

Here is a copy of the code with the user name and password changed

Code :

---

import java.sql.*;
import java.text.NumberFormat;
 
public class ListMovies
{
  public static void main(String[] args)
  {
    NumberFormat cf = NumberFormat.getCurrencyInstance();
 
    ResultSet movies = getMovies();
    try
    {
      while (movies.next())
      {
	Movie m = getMovie(movies);
	String msg = Integer.toString(m.year);
	msg += ": " +m.title;
	msg += " (" + cf.format(m.price) + ")";
	System.out.println(msg);
      }
    }
    catch (SQLException e)
    {
      System.out.println(e.getMessage());
    }
  }
 
  private static ResultSet getMovies()
  {
    Connection con = getConnection();
    try
    {
      Statement s = con.createStatement();
      String select = "Select title, year, price " + "from movie order by year";
      ResultSet rows;
      rows = s.executeQuery(select);
      return rows;
    }
    catch (SQLException e)
    {
      System.out.println(e.getMessage());
    }
    return null;
  }
 
  private static Connection getConnection()
  {
    Connection con = null;
 
    try 
    {
      Class.forName("com.mysql.jdbc.Driver");
      String url = "jdbc:mysql://myserver:3306/movies";
      String user = "user";
      String pw = "password";
      con = DriverManager.getConnection(url, user, pw);
    }
 
    catch (ClassNotFoundException e)
    {
      System.out.println(e.getMessage());
      System.exit(0);
    }
    catch (SQLException e)
    {
      System.out.println(e.getMessage());
      System.exit(0);
    }
    return con;
  }
 
  private static Movie getMovie(ResultSet movies)
  {
    try
    {
      String title = movies.getString("title");
      int year = movies.getInt ("year");
      double price = movies.getDouble("price");
      return new Movie(title, year, price);
    }
    catch (SQLException e)
    {
      System.out.println(e.getMessage());
    }
 
    return null;
  }
 
  private static class Movie
  {
    public String title;
    public int year;
    public double price;
    public Movie(String title, int year, double price)
    {
      this.title = title;
      this.year = year;
      this.price = price;
    }
  }
}

---

however when it is run the output i get is the following

Code :

---

com.mysql.jdbc.Driver

---

I realise that i'm probably missing something really simple but after several hours of looking i can't work it out :(

Print out the full exception stack trace...it has a lot more information than and will give you (and us) a much better sense as to the problem.

how do I go about doing that? sorry to sound thick!

The simplest way would by replacing the statement:
System.out.println(e.getMessage());
in all of your catch blocks with:
e.printStackTrace();

The Stack Trace will give you EVERYTHING you need to know about the exception.

right I think i get it

I have changed the code to show the following

Code :

---

 catch (ClassNotFoundException e)
    {
      System.out.println(e.getMessage());
      e.printStackTrace();
      System.exit(0);

---

and the output that I am receiving is the following

Code :

---

com.mysql.jdbc.Driver
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:186)
        at ListMovies.getConnection(ListMovies.java:52)
        at ListMovies.getMovies(ListMovies.java:30)
        at ListMovies.main(ListMovies.java:10)

---

Now to hit google to find out what the problem is, assuming this is what the problem is!

Did you download the jdbc driver and add it to your project's classpath?

Thanks for everyones help so far

It seems that it is an issue with the jdbc driver not being in the classpath. Now to work out how to get around this problem, there seems to be some debate as to whether or not it's wise to add it into the classpath as it's a global variable.

the relevent file appears to be /usr/share/java/mysql-jdbc/mysql-connector-java-5.1.18-bin.jar

Quote:

---

Originally Posted by aussiemcgr

Did you download the jdbc driver and add it to your project's classpath?

---

I'm using a text editor and bash rather than a full blown IDE to do this as my book doesn't cover any editors and they look a bit scary!

Quote:

---

there seems to be some debate as to whether or not it's wise to add it into the classpath as it's a global variable

---

I've never heard a debate (not denyong one does not exist, but please quote sources)...if you wish to deploy your application to other computers and platforms, its best practice to add the library to the class path.

PATH and CLASSPATH (The Java™ Tutorials > Essential Classes > The Platform Environment)

I have got it working (well i have got it working to the point that the server rejects the request) by setting $CLASSPATH with the following

Code :

---

CLASSPATH=.:../:/usr/share/java/mysql-jdbc/*
export CLASSPATH

---

does anyone know how to get $CLASSPATH to be set on boot? because every time I reboot I have to reset $CLASSPATH

thank you for all your help so far

See the link above - the preferred way of setting the classpath is not through an environmental variable, but by using the -cp command line option to javac and java