Java JDBC与MySQL的连接

Question

I am trying to connect to mysql from java web application in eclipse.

 Connection con = null; 

  try {
    //DriverManager.registerDriver(new com.mysql.jdbc.Driver());
    Class.forName("com.mysql.jdbc.Driver");
    con = DriverManager.getConnection("jdbc:mysql://localhost/db_name","root" ,"");

    if(!con.isClosed())
      System.out.println("Successfully connected to " +
        "MySQL server using TCP/IP...");

  } catch(Exception e) {
    System.err.println("Exception: " + e.getMessage());
  } finally {
    try {
      if(con != null)
        con.close();
    } catch(SQLException e) {
     System.out.println(e.toString());
    }
  }

I am always getting the Exception: com.mysql.jdbc.Driver

I have downloaded this jar http://forums.mysql.com/read.php?39,218287,220327

import it to the "java build path/lib"

the mysql version is 5.1.3 under.

running:

mysql 5.1.3 (db is up and running queries form PHP)

windows XP

Java EE

Answer 1

you say you placed the JAR on the build path, is it in the runtime class path? you said "java EE", so i assume you are deploying this as a web app? in that case you need to put the JDBC JAR file into WEB-INF/lib of your web app.

Answer 2

Have u added it in your build configuration also, if the location is not in classpath then it wont work by mere keeping it in lib folder. check your .classpath file

Answer 3

You can find a full documentation (Chapter 14) on how to connect to MySQL database through any web application (JBOSS, Glassfish etc...), if you download the MySQL JDBC driver . After doing your configuration, you have to get the connection from your server by getting your server connection ressource. Here is a sample code of how to get a connection ressource from a Glassfish server :

import java.sql.Connection;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ejb.Stateless;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;


@Stateless
public class AppConnection {
    private InitialContext context;
    private DataSource source;
    private Connection connection;   

    public AppConnection() {
        this.initConnection();
    }

    private void initConnection() {
        try {
            context = new InitialContext();            
            source = (DataSource)context.lookup("jdbc/MySQLDataSource");
            connection = source.getConnection();
        } catch (SQLException ex) {
            Logger.getLogger(AppConnection.class.getName()).log(Level.SEVERE, null, ex);
        } catch (NamingException ex) {
            Logger.getLogger(AppConnection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }        

    public Connection getContextConnection() {
        return connection;
    }

    public void closeContextConnection() throws SQLException {
        if(connection != null) {
            connection.close();
        }
    }
} 

Note that this class is an EJB and "jdbc/MySQLDataSource" is the name of the connection configured on your server. It can be inject in other EJB to get your current connection and create other needed objects as Statements or Resultsets .

Answer 4

You have to download the mysql jdbc connector und use it as lib. You can get it here:

http://www.mysql.com/downloads/connector/j/