DAO design pattern

LAAVANYA

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

DrRakha

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;
    }
}
 

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DAO design pattern