How to connect java database connection to many jFrames?

Question

I have created a class called DBConnection to connect the sql database. I also have a jFrame called AdminLogin. What I want to know is, how to pass the database connection to the AdminLogin class without having to type the whole database connection codes.

Here is my DBConnection class

package ltdasystem;

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



public class DBConnection {

    private Connection conn = null;
    private String query = null;
    private ResultSet rs;
    private final String url=("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase");
    private final String usrName = "sa";
    private final String pwd= "p@ssword13";

    public DBConnection() {
        try{
            conn = DriverManager.getConnection(url, usrName, pwd);
            query = "SELECT * from UserATable";
            PreparedStatement stm = conn.prepareStatement(query);
            rs = stm.executeQuery();
            while (rs.next()){
                String userName = rs.getString("Username");
                String password = rs.getString("Password");

                System.out.println("Username : " + userName + "\n" + "Password : " + password); 

            }
            conn.close();

        }catch (SQLException e){

          System.out.println(e.getMessage());

        }

    }

  }

Here is my AdminLogin. The way I have done it now works fine but I want to do it without having to type all the database connection codes.

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.swing.JOptionPane;


/**
 *
 * @author Yasitha
 */
public class AdminLogin extends javax.swing.JFrame {

     Connection conn = null;
     String query = null;
     ResultSet rs;
    private final String url=("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase");
    private final String usrName = "sa";
    private final String pwd= "p@ssword13";


    /**
     * Creates new form AdminLogin
     */
    public AdminLogin() {
        initComponents();
    }



    private void LoginButtonActionPerformed(java.awt.event.ActionEvent evt) {                                            
        //DBConnection db = new DBConnection();

       try{

             conn = DriverManager.getConnection(url, usrName, pwd);
             query = "SELECT * FROM UserATable WHERE Username = '" + userName.getText()
                    + "' AND Password = " + password.getText();


          PreparedStatement stm = conn.prepareStatement(query);
            rs = stm.executeQuery();
            if(rs.next()){
                dispose();
                String x = rs.getString("Username");
               AdminMenu admenu = new AdminMenu();
               admenu.setVisible(true);
               admenu.generate(x);

       }

       }catch (SQLException ex) {

           JOptionPane.showMessageDialog(null, ex);
           //return null;

        } finally {


        }   
    }                                           


        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new AdminLogin().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton BackButton;
    private javax.swing.JButton LoginButton;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPasswordField password;
    private javax.swing.JTextField userName;
    // End of variables declaration                   
}

Change `DBConnection` to be more like factory, which provides the means by which you can request it to make queries on your behalf. Use the constructor too seed the connection properties and then simply pass an instance of `DBConnection` to what ever classes need to make queries against the database — MadProgrammer, May 04 '15 at 04:33

score 3 · Answer 1 · edited May 23 '17 at 12:31

Change your design. DBConnection should be a factory/manger, which wraps the core functionality and management of the database connection and querying (or at least forms the bases of)

public interface DBConnection {

    public Connection getConnection() throws SQLException;

}

Then you could create query management classes or methods to handle the actually heavy lifting....

public class UserQueryManager {

    public boolean isValidUser(DBConnection dBConnection, String name, String password) throws SQLException {

        boolean isValidUser = false;
        try (Connection con = dBConnection.getConnection()) {

            try (PreparedStatement stmt = con.prepareStatement("select count(*) from UserATable where name=? and password=?")) {

                try (ResultSet rs = stmt.executeQuery()) {

                    if (rs.next()) {

                        int count = rs.getInt(1);
                        isValidUser = count > 0; // Maybe count == 1 would be more valid

                    }

                }

            }

        }

        return isValidUser;

    }

}

Now, we need a implementation of the DBConnection interface, something like...

public class DefaultDBConnection implements DBConnection {

    private final String url;
    private final String userName;
    private final String password;

    public DefaultDBConnection(String url, String userName, String password) {
        this.url = url;
        this.userName = userName;
        this.password = password;
    }

    @Override
    public Connection getConnection() throws SQLException {

        return DriverManager.getConnection(url, userName, password);

    }
}

Then you would create an instance of the DBConnection...

DefaultDBConnection dBConnection = new DefaultDBConnection("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase", "sa", "p@ssword13");

And pass it to your frame (or anybody else that might like to use it)

AdminLogin adminLogin = new AdminLogin(dBConnection);

You will then need to modify the AdminLogin to accept the parameter via the constructor...

public class AdminLogin extends javax.swing.JFrame {

    private DBConnection dBConnection;

    /**
     * Creates new form AdminLogin
     */
    public AdminLogin(DBConnection dBConnection) {
        this.dBConnection = dBConnection;
        initComponents();
    }

And the LoginButtonActionPerformed to setup the UserQueryManager and call the isValidUser...

private void LoginButtonActionPerformed(java.awt.event.ActionEvent evt) {
    try {
        UserQueryManager userQuertManager = new UserQueryManager();
        if (userQuertManager.isValidUser(dBConnection, userName.getText(), password.getText())) {
            dispose();
            AdminMenu admenu = new AdminMenu();
            admenu.setVisible(true);
            admenu.generate(userName.getText());
        }
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(null, ex);
        //return null;
    }
}

Beware, you really shouldn't be passing passwords around as Strings, but should be using char[] arrays.

Also, you might consider having a look at The Use of Multiple JFrames, Good/Bad Practice? and How to Use CardLayout

score 0 · Answer 2 · answered May 04 '15 at 08:43

Just want to add some change points here... isValidUser can be a static method since there is no state involved. Hence "UserQueryManager userQuertManager = new UserQueryManager()" new object creation on every button click will go...

Also dbconnection can be injected into UserQueryManager as a interface member. Also to the prime questioner..if you look at these classes with a MVC kind of perspective then the break up of code would be nicer if you look at the

AdminLogin which is a frame as a View component ...hence it is not very clean to see DBConnection or QueryManager objects as member variables of the this component.

How to connect java database connection to many jFrames?

2 Answers2