带有Tomcat7的Eclipse Juno Java EE IDE-ClassNotFoundException

Question

I have a webapp installed and running but everytime I attempt to connect to the MySQL database using JDBC connection I get a CLASSnotFOUNDexception.

The mysql-java-connector jar is in my WEB-INF/classes as well as WEB-INF/lib folders. Its on Eclipse's Build path as well but somehow the jar is not being deployed. I've tried adding the jar separately to the build path as well. I've been stuck here for quite a well.

Can someone direct me on how to deploy the jar?

Heres part of the code I use to connect with my database.

public class JdbcConnection {
    public Connection connection;

    public JdbcConnection(){
        String serverLocation = "";
        String db = "";
        String user = "";
        String password = "";

        try{
            InputStream in = JdbcConnection.class.getResourceAsStream("/props/database.properties") ;
            Properties props = new Properties();
            props.load(in);
            serverLocation = props.getProperty("serverLocation");
            db = props.getProperty("db");
            user = props.getProperty("user");
            password = props.getProperty("password");
            System.out.println(password + user + db + serverLocation);
           } 
        catch(Exception e){
            System.out.println("error" + e);
           }     

        createConnection(serverLocation, db, user, password);
    }

    public JdbcConnection(String serverLocation, String db, String user, String password){
        createConnection(serverLocation, db, user, password);
    }

Here is the error that comes up in the console. java.lang.ClassNotFoundException: com/mysql/jdbc/Driver

Here is the create connection method

public void createConnection (String serverLocation, String db, String user, String password){
    //register driver
    try {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
    } catch (InstantiationException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (IllegalAccessException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (ClassNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    //              hostName = "jdbc:mysql://" + serverLocation+"/"+db+"?autoReconnect=true";
    String hostName = "jdbc:mysql://" + serverLocation+"/"+db+"?autoReconnect=true&useUnicode=yes&characterEncoding=UTF-8";
    try {
        connection = DriverManager.getConnection(hostName,user,password);
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }   
}

Answer 1

Tomcat 6.x and higher demands that you put all JDBC driver JARs in its /lib directory.

Remove it from WEB-INF/classes (it does no good there, anyway) and WEB-INF/lib, redeploy your WAR, and you'll be able to move onto your next error.

Believe me, you're still doing it wrong. It will work if you do it properly.

I'd recommend doctoring this class and making a connection to MySQL without Eclipse or Tomcat. If you can manage that, move up the ladder one step.

package persistence;

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

/**
 * util.DatabaseUtils
 * User: Michael
 * Date: Aug 17, 2010
 * Time: 7:58:02 PM
 */
public class DatabaseUtils {
/*
    private static final String DEFAULT_DRIVER = "oracle.jdbc.driver.OracleDriver";
    private static final String DEFAULT_URL = "jdbc:oracle:thin:@host:1521:database";
    private static final String DEFAULT_USERNAME = "username";
    private static final String DEFAULT_PASSWORD = "password";
*/
/*
    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<String, Object>> map(ResultSet rs) throws SQLException {
        List<Map<String, Object>> results = new ArrayList<Map<String, Object>>();
        try {
            if (rs != null) {
                ResultSetMetaData meta = rs.getMetaData();
                int numColumns = meta.getColumnCount();
                while (rs.next()) {
                    Map<String, Object> row = new HashMap<String, Object>();
                    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<Map<String, Object>> query(Connection connection, String sql, List<Object> parameters) throws SQLException {
        List<Map<String, Object>> results = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            ps = connection.prepareStatement(sql);

            int i = 0;
            for (Object parameter : parameters) {
                ps.setObject(++i, parameter);
            }
            rs = ps.executeQuery();
            results = map(rs);
        } finally {
            close(rs);
            close(ps);
        }
        return results;
    }

    public static int update(Connection connection, String sql, List<Object> parameters) throws SQLException {
        int numRowsUpdated = 0;
        PreparedStatement ps = null;
        try {
            ps = connection.prepareStatement(sql);

            int i = 0;
            for (Object parameter : parameters) {
                ps.setObject(++i, parameter);
            }
            numRowsUpdated = ps.executeUpdate();
        } finally {
            close(ps);
        }
        return numRowsUpdated;
    }
}