请高人指教到底错哪了呢？

请高人指教到底哪里错了呢？？？

package cn.itcast.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import cn.itcast.exception.DaoException;
import cn.itcast.utils.JdbcUtils;

public class UserDaoJdbcImpl implements UserDao {

	public void add(User user) {
		// TODO Auto-generated method stub
		Connection conn=null;
		PreparedStatement st=null;
		ResultSet rs=null;
		
		try {
			conn=JdbcUtils.getConnection();
			String sql="insert into users(id,username,password,email,birthday) values(?,?,?,?,?)";
			st=conn.prepareStatement(sql);
			st.setString(1,user.getId());
			st.setString(2,user.getUsername());
			st.setString(3, user.getPassword());
			st.setString(4,user.getEmail());
			st.setDate(5,new java.sql.Date(user.getBirthday().getTime()));
			
			st.executeUpdate(sql);
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			JdbcUtils.release(conn, st, rs);
		}
	}

	public User find(String username, String password) {
		Connection conn=null;
		PreparedStatement st=null;
		ResultSet rs=null;
		
		try {
			conn=JdbcUtils.getConnection();
			String sql="select * from users where username=? and password=?";
			st=conn.prepareStatement(sql);
			st.setString(1,username);
			st.setString(2,password);
			
			rs=st.executeQuery();
			if(rs.next()){
				User user=new User();
				user.setId(rs.getString("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setEmail(rs.getString("email"));
				user.setBirthday(rs.getDate("birthday"));
				return user;
			}
			return null;
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			throw new DaoException(e);
		}finally{
			JdbcUtils.release(conn, st, rs);
		}
	}

	public User find(String username) {
		// TODO Auto-generated method stub
		Connection conn=null;
		PreparedStatement st=null;
		ResultSet rs=null;
		
		try {
			conn=JdbcUtils.getConnection();
			String sql="select * from users where username=?";
			st=conn.prepareStatement(sql);
			st.setString(1,username);
			
			rs=st.executeQuery();
			if(rs.next()){
				User user=new User();
				user.setId(rs.getString("id"));
				user.setUsername(rs.getString("username"));
				user.setPassword(rs.getString("password"));
				user.setEmail(rs.getString("email"));
				user.setBirthday(rs.getDate("birthday"));
				return user;
			}
			return null;
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			throw new DaoException(e);
		}finally{
			JdbcUtils.release(conn, st, rs);
		}
	}

}

错误信息：2013-10-12 22:12:55 org.apache.catalina.startup.HostConfig checkResources
信息: Reloading context [/myday14_user]
com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?,?,?,?,?)' at line 1
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:936)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2985)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1631)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3277)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1402)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1317)
at cn.itcast.dao.impl.UserDaoJdbcImpl.add(UserDaoJdbcImpl.java:32)
at cn.itcast.service.impl.BusinessServiceImpl.registerUser(BusinessServiceImpl.java:25)
at cn.itcast.web.controller.RegisterServlet.doGet(RegisterServlet.java:47)
at cn.itcast.web.controller.RegisterServlet.doPost(RegisterServlet.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)