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urgent, please help!got problem of connecting to mysql database using JDBC

Discussion in 'Plesk for Linux - 8.x and Older' started by raybristol, Apr 13, 2006.

  1. raybristol

    raybristol Guest

    hi, I got problem of connecting to mysql database using JDBC,I list what I did step by step and hoping you can tell me whether I did anything wrongly:

    1. I have a jsp project called test4, I copy file 'mysql-connector-java-3.1.6-bin.jar' to folder 'test4\WEB-INF\lib'

    2. export the whole project in war format: test4.war

    3. upload it to live server

    4. restart tomcat

    at this point, I got ' java.lang.NullPointerException ' when try to connect the database.

    5. I notice in the live server, in file 'tomcat4/conf/catalina.policy', I saw a example of granting the permission to a JDBC driver, so I adding the following in file 'catalina.policy':

    grant codeBase "file:${catalina.home}/psa-webapps/test4/WEB-INF/lib/mysql-connector-java-3.1.6-bin.jar"{
    permission java.net.SocketPermission "localhost:3306", "connect";
    permission java.net.SocketPermission "", "connect";

    but I still got the same exception 'java.lang.NullPointerException', I wonder if I did that wrong in policy file or anyother reason? I can't anything wrong in my code as it works perfectly in my machine, so it must be something else, I think the username and password should be correct.

    Many thanks for your help!

    In my development machine, I got no problem at all, in live server, the user name and password also right, as when I entering the live server login as root, I can do commmand 'mysql -urui -pchangeme Spottheballtv' with no problem, so I wonder how do I get more information to solve this problem?

    exception 'java.lang.NullPointerException' doesn't give me too much helpful information for debugging, so I wonder what else Exception I need to catch in order to get more useful information?

    Many thanks for your help again!


    my code is very simple:

    <%@ page language="java" pageEncoding="UTF-8"%>
    <%@ page import="java.sql.*" %>
    <%@ page import="javax.sql.DataSource" %>
    <%@ page import="payment.DbConnect" %>

    java.sql.Connection con = null;
    Statement stmt = null;
    con=DbConnect.connectToDb("localhost", "Spottheballtv","rui","changeme");
    stmt = con.createStatement();
    //String query = "SELECT * FROM Ticket";
    //ResultSet rs = stmt.executeQuery(query);
    catch (Exception ex)

    my connection class:
    package payment;

    import java.sql.*;

    public class DbConnect {
    static String driverName = "com.mysql.jdbc.Driver";
    static String dbUrl = "jdbc:mysql://";

    public DbConnect() {

    public static java.sql.Connection connectToDb(String hostName,String databaseName, String uid, String pw) throws Exception {
    Connection conn = null;
    String connName = dbUrl+hostName+":3306"+"/"+databaseName;
    conn = DriverManager.getConnection(connName+"?useUnicode=true&characterEncoding=GBK",uid,pw);
    } catch (Exception e){ e.printStackTrace();}
    return conn;
  2. wagnerch

    wagnerch Guest

    Does your /etc/my.cnf have "skip-networking" in the configuration file? JDBC doesn't leverage UNIX sockets, so it has to use TCP/IP. The default installation of MySQL is to NOT use the TCP/IP socket (3306).
  3. raybristol

    raybristol Guest

    Hi, thanks you so sooooooooooo much for your reply!!!!!!!!

    I will check it soon and let you know how it goes, many many thanks again!!!!!!!