JDBC and MySQL connectivity problem

Question

The code i hav attached generates Connectivity exception.. the prob is with the part in bold.. can anyone help
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class testconn {
  public static void main(String args[]) {
    Connection con = null;
            String serverName = "localhost:8080";
        String mydatabase = "imagedb";
        String url = "jdbc:mysql://" + serverName +  "/" + mydatabase; // a JDBC url
        String username = "am";
        String password = "ta";
    try {
      Class.forName("com.mysql.jdbc.Driver");
     con= DriverManager.getConnection(url, username, password);
      if(!con.isClosed())
        System.out.println("Successfully connected to " +
          "MySQL server using TCP/IP...");
    } catch(Exception e) {
      System.err.println("Exception: " + e);
    } finally {
      try {
        if(con != null)
          con.close();
      } catch(SQLException e) {}
}

Answer 1

I had such issue too, and I fixed it by adding in the environment variables the CLASSPATH entry that pointed to all the directories containing the .jar needed for the applications.
for example I used jodbc folder to connect mysql database (I installed last version and I got same issue than yours and it seems to be a 'connector' issue, exactly the same issue than yours) I got something like
CLASSPATH=my root dir/the java dir/the lib dir/jodbc;my root dir/the java dir/other important libs containing .jar files;
This is what I got for the issue, still working around (at the level of mysql all is ok, ...)
Microsoft Windows XP [version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\Hurukan>java ConnectJODBC brol
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at ConnectJODBC.main(ConnectJODBC.java:108)
[exception] -- la valeur de 'con' est nulle (DriverManager � retourn� une valeur
nulle)
C:\Documents and Settings\Hurukan>set
APPDATA=C:\Documents and Settings\Hurukan\Application Data
CLASSPATH=c:\Program Files\Java\jdk1.5.0_06\lib;c:\Program Files\Java\jdk1.5.0_06\dev;\c:\Program Files\Java\jdk1.5.0_06\lib\jodbc;
Here is the code that generated this exception
String dburl="jdbc:mysql://127.0.0.1/nosdisques"; // should be next passed by command line
String password="**scrambled**";
String username="**scrambled**";
Connection con=null;
Statement stmt=null;
ResultSet res=null;
String requete="";
String strToWrite="";
// Connexion � la base de donn�e
// Won't work with mysql 5.0.18, mysql connector 3.51.12 is installed [???]
// Previous tests with 5.0.18 were running good, that has started with the last os restoration (and the connector was different of course...)
// tried to retreive older version of the mysql connector
try
Class.forName("com.mysql.jdbc.Driver").newInstance();
con=DriverManager.getConnection(dburl,username,password);
System.out.println("Nous sommes connect\u201as \u2026 la base " + con.getCatalog());
catch(SQLException sqlex)
System.out.println("[sqlexception]\n");
System.exit(3);
catch(Exception ex)
ex.printStackTrace();
if(con == null)
System.out.println("[exception] -- la valeur de 'con' est nulle (DriverManager \u2026 retourn\u201a une valeur nulle)\n");
System.exit(4);
System.out.println("Impossible to join database, access denied\n");
System.out.println("Verify settings (mysqld or firewall)\n"); System.exit(2);
Maybe the drivers used (last one: connector/j 3.1.12). The .jar file is in the %classpath% directory c:\Program Files\Java\jdk1.5.0_06\lib.
Can't really understand why this code won't run anymore, ...
I took a look on the other computer where the same code is running ok.
These are the differences:
mysql server is 5.0.18 on the other computer the version is 3.23.41
mysql connector is 3.51.12 on the other computer the version is 3.0.10
access rights are the same because the database is the dumped one from 3.23.41 to 5.0.18, and I'm quite good with the dbms management (I'm IT developper in fact, trying to take over java technology ;) )
in this case this is not a sql error but java error.
the jar file is set to the %classpath% folder on both computers
I copied the jar from the other computer, removing the new .jar file and... it failed, exactly the same issue
Still working around, ...
Dimitri