[SOLVED] Mysql + Java (JDBC driver problem)

hBd · 2010-03-05 14:31:34

Hello!
I want to connect to mysql server with Java, but i got an error like this:
Exception in thread "main" java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

I found in Wiki some instruction, i installed mysql-jdbc from AUR but does not work :S

Can someone help me to get this work ?

PS. i try with the program from the wiki

import java.sql.*;
import java.util.Properties;
public class DBDemo
{
 // The JDBC Connector Class.
 private static final String dbClassName = "com.mysql.jdbc.Driver";
 // Connection string. emotherearth is the database the program
 // is connecting to. You can include user and password after this
 // by adding (say) ?user=paulr&password=paulr. Not recommended!
 private static final String CONNECTION =
                         "jdbc:mysql://127.0.0.1/emotherearth";
 public static void main(String[] args) throws
                            ClassNotFoundException,SQLException
 {
   System.out.println(dbClassName);
   // Class.forName(xxx) loads the jdbc classes and
   // creates a drivermanager class factory
   Class.forName(dbClassName);
   // Properties for user and password. Here the user and password are both 'paulr'
   Properties p = new Properties();
   p.put("user","paulr");
   p.put("password","paulr");
   // Now try to connect
   Connection c = DriverManager.getConnection(CONNECTION,p);
   System.out.println("It works !");
   c.close();
   }
}

Last edited by hBd (2010-03-06 19:29:48)

SiC · 2010-03-05 15:49:33

Your JDBC .jar file is not in the class path. Try setting the classpath to the folder where the file is and run the Java app again

so

CLASSPATH=/path/to/jdbc/driver:$CLASSPATH java -jar myapp.jar

would work

hBd · 2010-03-05 16:18:33

Thanks for the help, i make it different but u show me the way
I make a link ln -s /usr/share/java/mysql-jdbc/mysql-connector-java-bin.jar $JAVA_HOME/jre/lib/ext/
and it works but now i get another error msg :S

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1119)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2257)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:784)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:354)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:284)
    at java.sql.DriverManager.getConnection(DriverManager.java:582)
    at java.sql.DriverManager.getConnection(DriverManager.java:154)
    at DBDemo.main(DBDemo.java:24)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1119)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:343)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2178)
    ... 12 more
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
    at java.net.Socket.connect(Socket.java:525)
    at java.net.Socket.connect(Socket.java:475)
    at java.net.Socket.<init>(Socket.java:372)
    at java.net.Socket.<init>(Socket.java:215)
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:253)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:292)
    ... 13 more

hmm hmm

n0dix · 2010-03-05 21:33:26

Googling this issue you will get thousands of topics related to it.

hBd · 2010-03-06 10:29:51

i did, but nothing help me, for now :S
ps. im not that stupid, i search before ask

Last edited by hBd (2010-03-06 10:30:35)

Gruntz · 2010-03-06 17:15:09

Did someone found a solution to this issue. I have the same problem like in the 3# post here and I am looking for a solution now.

Can anyone give me a hint?

Loke · 2010-03-06 18:11:43

I had a similar issue a while back - which I solved by commenting out "skip-networking" in my.cnf. Not sure if it will solve your issue as well, but you could give it a try.

(mysqld needs restart after the changes have been made, obviously.)

Last edited by Loke (2010-03-06 18:12:44)

hBd · 2010-03-06 18:38:17

cat /etc/my.cnf | grep skip-networking
#skip-networking

should look like this, not ? not work... :S
the mysqld is up, and running. i can acces trought phpmyadmin...

hBd · 2010-03-06 19:29:02

Finally it works now! The problem was the skip-networking option, it was commented at /etc/my.cnf but mysql use the /etc/mysql/my.cnf conf file, and there was not commented. I figure it out that 3306 port was not open,

sudo nmap -p 3306 localhost

Starting Nmap 5.21 ( http://nmap.org ) at 2010-03-06 21:18 EET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000036s latency).
rDNS record for 127.0.0.1: localhost.localdomain
PORT     STATE  SERVICE
3306/tcp closed mysql

after i commented out, that line, and restarted the mysqld it works perfectly, and the java app to!

sudo nmap -p 3306 localhost

Starting Nmap 5.21 ( http://nmap.org ) at 2010-03-06 21:24 EET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000041s latency).
rDNS record for 127.0.0.1: localhost.localdomain
PORT     STATE SERVICE
3306/tcp open  mysql

Nmap done: 1 IP address (1 host up) scanned in 0.09 seconds

hope that helps u guys to! i think the post can be renamed to SOLVED!

Loke · 2010-03-06 19:42:23

I'm glad it helped

And yeah it's a while since the configuration was moved; http://www.archlinux.org/news/473/

Gruntz · 2010-03-06 19:46:03

hBd, thank you man. That solvet my problem too. But i had it the other way. The network option was commented in /etc/mysql/my.cnf conf and not commented in /etc/my.cnf. I uncommented in both files and it worked.

Thank you.

Arch Linux

#1 2010-03-05 14:31:34

[SOLVED] Mysql + Java (JDBC driver problem)

#2 2010-03-05 15:49:33

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#3 2010-03-05 16:18:33

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#4 2010-03-05 21:33:26

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#5 2010-03-06 10:29:51

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#6 2010-03-06 17:15:09

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#7 2010-03-06 18:11:43

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#8 2010-03-06 18:38:17

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#9 2010-03-06 19:29:02

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#10 2010-03-06 19:42:23

Re: [SOLVED] Mysql + Java (JDBC driver problem)

#11 2010-03-06 19:46:03

Re: [SOLVED] Mysql + Java (JDBC driver problem)

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