DAO design pattern

LAAVANYA · **Posted:** Sat Apr 09, 2011 5:04 am

sir please explain me what is DAO design pattern and when to use this design pattern in struts or hibernate

msi_333 · **Posted:** Sat Apr 09, 2011 10:53 am

The idea is to separate the data access functions and to put them in DAO class ,
in hibernate , you put named queries in orm.xml and call it by name in your entityManager .
DAO general ideaExample.

Code:

/*
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package mailtest.dao;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;
import mailtest.config.DateUtils;
import mailtest.customgui.GUILogger;
import mailtest.data.IReservation;

/**
 *
 * @author Mohamed.Sami
 */
public class DOA {

    private static DOA doa;
    private GUILogger gUILogger = GUILogger.getInstance();

    private DOA() {
    }

    public void insertReservations(Vector<IReservation> reservationVector) {

        if (reservationVector == null || reservationVector.size() == 0) {
            JOptionPane.showMessageDialog(null,
                    "No reservations avaliable to insert to database.",
                    "Database Error Message",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        ConnectionManager connectionManager = ConnectionManager.getInstance();

        Connection connection = connectionManager.getOracleConnection();

        if (connection != null) {
            try {
                Statement statement = (Statement) connection.createStatement();


                String query = "select max(ID) from TRKIN";
                ResultSet resultSet = statement.executeQuery(query);
                resultSet.next();
                int success = 0;
                int failure = 0;
                int duplicate = 0;
                long idmax = resultSet.getLong(1);
                System.out.println("max = " + idmax);
                for (IReservation iReservation : reservationVector) {
                    try {

                        resultSet = statement.executeQuery("select * from TRKIN where AIRCODE='" + iReservation.getAirlineCode() + "' and PNR='" +
                                iReservation.getReservationNumber() + "' ");
                        if (resultSet.next()) {
                            duplicate++;
                            continue;
                        }
                        query = "insert into TRKIN (ID,AIRCODE,PNR,ISS_DT,LOC_CD,PAX,SECTOR,FARE,TAX,COMM,NET,"
                                + "ITINERARY,SELL_AMT,LPO,CUS_CODE,STATUS,ORIGINAL_DOC,CURRENCY) " + "VALUES (" + (++idmax) + ",'" +
                                iReservation.getAirlineCode() + "','" + iReservation.getReservationNumber() + "',"
                                + "'" + DateUtils.formateDate(iReservation.getReservationDate(), "dd/MMM/yy") + "','0','" + iReservation.getClientName() + "','0'," +
                                ((iReservation.getFare() == null) ? 0 :
                                    iReservation.getFare().getPaymentAmount()) + ",0,0," + iReservation.getPaymentAmount().getPaymentAmount() + ","
                                + "'From:" + iReservation.getItineraryFrom() + ((iReservation.getItineraryTo() == null) ? "" : ",To:" + iReservation.getItineraryTo()) + "',"
                                + "'0','0','0','0','0','" + iReservation.getPaymentAmount().getCurrency() + "')";
                        System.out.println("Query to be excuated " + query);
                        statement.executeUpdate(query);
                        success++;
                    } catch (SQLException ex) {
                        failure++;
                        Logger.getLogger(DOA.class.getName()).log(Level.SEVERE, null, ex);
                        JOptionPane.showMessageDialog(null,
                                " Failed to insert due to SQL error." + ex,
                                "Database confirmation", JOptionPane.ERROR_MESSAGE);

                        gUILogger.logInfo("Failed to insert due to SQL error." + ex);
                    }

                }

                if(resultSet!=null){
                    resultSet.close();
                }
                if(statement!=null)
                statement.close();
                gUILogger.logInfo(
                        "Reservation inserting to database is compeleted. Success(" + success + "),Failure(" + failure + ")" + " ,Duplicate(" + duplicate + ").");
               
               

            } catch (Exception ex) {
                Logger.getLogger(DOA.class.getName()).log(Level.SEVERE, null, ex);
                JOptionPane.showMessageDialog(null,
                        " Failed to insert due to error ." + ex,
                        "Database confirmation", JOptionPane.ERROR_MESSAGE);

                gUILogger.logInfo("Failed to insert due to SQL error." + ex);
            } 


        } else {
            JOptionPane.showMessageDialog(null,
                    " couldn't connect to database .",
                    "Database confirmation", JOptionPane.ERROR_MESSAGE);
        }

    }

    public static DOA getInstance() {
        if (doa == null) {
            doa = new DOA();

        }
        return doa;
    }
}

 

Code:

import java.io.File;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;
import mailtest.config.PropertiesUtility;
import mailtest.customgui.GUILogger;

/**
 *
 * @author Mohamed.Sami
 */
public class ConnectionManager {

    private String url;
    private String username;
    private String password;
    private String propertiesFile = "./props/database.properties";
    private Properties properties = null;
    private GUILogger gUILogger = GUILogger.getInstance();
    private static Connection oracleConnection = null;
    private static ConnectionManager connectionManager;

    private ConnectionManager() {
    }

    public Connection getOracleConnection() {
        try {

            if (oracleConnection != null) {
                return oracleConnection;
            }
            properties = PropertiesUtility.load(new File(propertiesFile));
            if (properties == null) {
                JOptionPane.showMessageDialog(null,
                        "Couldn't load database connection properties.",
                        "Database Error Message",
                        JOptionPane.ERROR_MESSAGE);
                return null;
            }

            DriverManager.registerDriver(
                    new oracle.jdbc.OracleDriver());
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
            gUILogger.logInfo("Requesting database connection");
            oracleConnection = DriverManager.getConnection(url, username, password);

            if (oracleConnection != null) {
                gUILogger.logInfo("Connection to database is opened.");
            } else {

                gUILogger.logInfo("Connection to database failed.\n"
                        + "url = " + url + " \n"
                        + "username=" + username + ""
                        + "password=" + password);
                JOptionPane.showMessageDialog(null,
                        "Connection to database failed.\n"
                        + "url = " + url + " \n"
                        + "username=" + username + ""
                        + "password=" + password,
                        "Database Error Message.",
                        JOptionPane.ERROR_MESSAGE);
            }




//            conn.setAutoCommit(false);
//            Statement stmt = conn.createStatement();
//            ResultSet rset = stmt.executeQuery("select BANNER from SYS.V_$VERSION");
//            while (rset.next()) {
//                System.out.println(rset.getString(1));
//            }
//            stmt.close();

        } catch (SQLException ex) {
            JOptionPane.showMessageDialog(null,
                    "Connection to database failed." + ex,
                    "Database Error Message :",
                    JOptionPane.ERROR_MESSAGE);
            Logger.getLogger(ConnectionManager.class.getName()).log(Level.SEVERE, null, ex);
        } catch (Exception ex) {
            ex.printStackTrace();
            JOptionPane.showMessageDialog(null,
                    "Connection to database failed." + ex,
                    "Database Error Message :",
                    JOptionPane.ERROR_MESSAGE);
            Logger.getLogger(ConnectionManager.class.getName()).log(Level.SEVERE, null, ex);
        }
        return oracleConnection;
    }

    public String getPassword() {
        return password;


    }

    public void setPassword(String password) {
        this.password = password;


    }

    public String getUrl() {
        return url;


    }

    public void setUrl(String url) {
        this.url = url;


    }

    public String getUsername() {
        return username;


    }

    public void setUsername(String username) {
        this.username = username;


    }

    @Override
    public void finalize() {
//        if (oracleConnection != null) {
//            try {
//                oracleConnection.close();
//
//
//
//            } catch (SQLException ex) {
//                Logger.getLogger(ConnectionManager.class.getName()).log(Level.SEVERE, null, ex);
//            }
//
//
//        }
    }

    public static ConnectionManager getInstance() {

        if (connectionManager == null) {
            connectionManager = new ConnectionManager();
        }

        return connectionManager;
    }
}
 

DAO design pattern

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