How can I resolve java.lang.NoClassDefFoundError?

Question

I am new to Java and have installed it on my Linux Ubuntu 9.04 workstation in order to learn Java. Basic Java programs work, but I am having trouble connecting to a MySQL database. I installed these packages using Synaptic Package Manager, which I thought should cover everything I need for database connectivity: 1.gsfonts-x11; 2.java-common; 3.odbcinst1debian1; 4.sun-java6-bin; 5.sun-java6-jdk; 6.sun-java6-jre; 7.unixodbc.
After these packages were installed, I was not sure if I needed to do this, but I downloaded the MySQL connector from http://www.mysql.com/products/connector/ and installed in a directory called /home/mark/mysql/.
I edited /etc/environment" and added a CLASSPATH to where I installed the connector:
{code}CLASSPATH="/home/mark/mysql/mysql-connector-java-5.1.7/mysql-connector-java-5.1.7-bin.jar"
{code}
I created a very simple Java program based on one I found on the internet. I named the program Jdbctest to test the connection,
{code}import java.sql.*;
public class Jdbctest {
public static void main(String[] args){
System.out.println("running Jdbctest.java");
try {
Statement stmt;
//Register the JDBC driver for MySQL.
Class.forName("com.mysql.jdbc.Driver");
//Define URL of database server for database named mysql
// on the localhost with the default port number 3306.
String url = "jdbc:mysql://localhost:3306/mysql";
//Get a connection to the database for a
// user named root with password carrot.
// This user is the default administrator
// having full privileges to do anything.
Connection con = DriverManager.getConnection(url,"root", "carrot");
//Display URL and connection information
System.out.println("URL: " + url);
System.out.println("Connection: " + con);
//Get a Statement object
stmt = con.createStatement();
//Select from a table
stmt.executeQuery("SELECT host, user FROM mysql.user ");
con.close();
}catch( Exception e ) {
e.printStackTrace();
}//end catch
}//end main
}//end class Jdbctest{code}
but I get this error:
{code}Exception in thread "main" java.lang.NoClassDefFoundError: Jdbctest
Caused by: java.lang.ClassNotFoundException: Jdbctest
     at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
     at java.security.AccessController.doPrivileged(Native Method)
     at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
     at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
Could not find the main class: Jdbctest. Program will exit.{code}
I don't really understand what this error message is telling me. I've Googled for an explanation, and it seems to indicate that my CLASSPATH is wrong, but I'm not sure what it should be and how to fix it. Any assistance would be greatly appreciated.

Answer 1

Your class JdcbTest isn't in that JAR, is it? So you need the CLASSPATH to also specify where that is. Typical CLASSPATHs start with a dot and then some jars.