Why is java.sql.DriverManager.getConnection(…) hanging?

Question

I am attempting to get a connection to my University\'s MySQL DB but the connection is hanging.

import java.sql.*;

public class ConnectToDB {
        publ         


        

Answer 1

The output you provide is not helpful.

I see BEFORE and AFTER being printed, so the connection was made. The code doesn't show what those timings encompass, so I can't tell what they mean.

If you're suggesting that your code had to killed because the connection was never made, it's probably because your username, password, and client IP have not been GRANTed permissions that are needed.

Could be:

1. your university network; find a network engineer to ask about firewalls.
2. permission in the MySQL database; find the DBA and ask.
3. your code; you didn't post enough to tell. Post the whole class.

What's up with that copyright? I'd lose that.

This code works. Modify it so the pertinent parameters match your problem. (Mine uses MySQL 5.1.51 and a table named Party.) When I run it on my local machine, I get a wall time of 641 ms.

package persistence;

import java.sql.*;
import java.util.*;

/**
 * DatabaseUtils
 * User: Michael
 * Date: Aug 17, 2010
 * Time: 7:58:02 PM
 */
public class DatabaseUtils
{
/*
    private static final String DEFAULT_DRIVER = "org.postgresql.Driver";
    private static final String DEFAULT_URL = "jdbc:postgresql://localhost:5432/party";
    private static final String DEFAULT_USERNAME = "pgsuper";
    private static final String DEFAULT_PASSWORD = "pgsuper";
*/
    private static final String DEFAULT_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DEFAULT_URL = "jdbc:mysql://localhost:3306/party";
    private static final String DEFAULT_USERNAME = "party";
    private static final String DEFAULT_PASSWORD = "party";

    public static void main(String[] args)
    {
        long begTime = System.currentTimeMillis();

        String driver = ((args.length > 0) ? args[0] : DEFAULT_DRIVER);
        String url = ((args.length > 1) ? args[1] : DEFAULT_URL);
        String username = ((args.length > 2) ? args[2] : DEFAULT_USERNAME);
        String password = ((args.length > 3) ? args[3] : DEFAULT_PASSWORD);

        Connection connection = null;

        try
        {
            connection = createConnection(driver, url, username, password);
            DatabaseMetaData meta = connection.getMetaData();
            System.out.println(meta.getDatabaseProductName());
            System.out.println(meta.getDatabaseProductVersion());

            String sqlQuery = "SELECT PERSON_ID, FIRST_NAME, LAST_NAME FROM PERSON ORDER BY LAST_NAME";
            System.out.println("before insert: " + query(connection, sqlQuery, Collections.EMPTY_LIST));

            connection.setAutoCommit(false);
            String sqlUpdate = "INSERT INTO PERSON(FIRST_NAME, LAST_NAME) VALUES(?,?)";
            List parameters = Arrays.asList( "Foo", "Bar" );
            int numRowsUpdated = update(connection, sqlUpdate, parameters);
            connection.commit();

            System.out.println("# rows inserted: " + numRowsUpdated);
            System.out.println("after insert: " + query(connection, sqlQuery, Collections.EMPTY_LIST));
        }
        catch (Exception e)
        {
            rollback(connection);
            e.printStackTrace();
        }
        finally
        {
            close(connection);
            long endTime = System.currentTimeMillis();
            System.out.println("wall time: " + (endTime - begTime) + " ms");
        }
    }

    public static Connection createConnection(String driver, String url, String username, String password) throws ClassNotFoundException, SQLException
    {
        Class.forName(driver);

        if ((username == null) || (password == null) || (username.trim().length() == 0) || (password.trim().length() == 0))
        {
            return DriverManager.getConnection(url);
        }
        else
        {
            return DriverManager.getConnection(url, username, password);
        }
    }

    public static void close(Connection connection)
    {
        try
        {
            if (connection != null)
            {
                connection.close();
            }
        }
        catch (SQLException e)
        {
            e.printStackTrace();
        }
    }


    public static void close(Statement st)
    {
        try
        {
            if (st != null)
            {
                st.close();
            }
        }
        catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

    public static void close(ResultSet rs)
    {
        try
        {
            if (rs != null)
            {
                rs.close();
            }
        }
        catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

    public static void rollback(Connection connection)
    {
        try
        {
            if (connection != null)
            {
                connection.rollback();
            }
        }
        catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

    public static List> map(ResultSet rs) throws SQLException
    {
        List> results = new ArrayList>();

        try
        {
            if (rs != null)
            {
                ResultSetMetaData meta = rs.getMetaData();
                int numColumns = meta.getColumnCount();
                while (rs.next())
                {
                    Map row = new HashMap();
                    for (int i = 1; i <= numColumns; ++i)
                    {
                        String name = meta.getColumnName(i);
                        Object value = rs.getObject(i);
                        row.put(name, value);
                    }
                    results.add(row);
                }
            }
        }
        finally
        {
            close(rs);
        }

        return results;
    }

    public static List> query(Connection connection, String sql, List