使用 JDBC 插入 JButton

Question

I would like to know is it possible to extract the data from the database file and directly put it in the JButton to let the user select?

For example,

The first GUI will let the user click a JButton (Food).

Then the second GUI will prompt out all the names from the database.

Is it possible to do that?

Can I have a sample code? Just a simple one will do.

Answer 1

Hey in this case I explain how to display Employee information from a database in a Frame. The NetBeans IDE is used for creating this application.

How to Display Emp Information in a New Frame

For creating this app we need the following files.

Java file ojdbc.jar file NetBeans IDE SQL table

1. Java File

This Java contains the programming code. In this file we use Swing components to display the emp data in a new frame after the employee name selection.

What we can do

A. Import several packages

First we need to import the following packages:

javax.swing.*;
java.awt.*;
java.awt.event.*;
java.sql.*;
java.util.Vector;

The Swing package is used for the swing components. All swing components are defined within this package. The AWT package provides the event handling mechanism, in other words it deals with events like "button-click". The SQL package creates the JDBC connection.

B. Extend the JFrame components and implements the ActionListener

Extends the JFrame components and implement the ActionListener as in the following:

class EmpSearchApp extends JFrame implements ActionListener

C. Declare components

Now declare the following components:

JLabel l, l1, l2, l3, l4,l5;

JButton b;

JTextField tf1, tf2, tf3, tf4;

JComboBox bx;
String str;

D. Declare Frame components

Now declare Frame components in a default constructor as in the following:

Syntax

EmpSearchApp()
{
......
......
try{
//JDBC CODE
}Catch(Exception ex)
{
System.out.println(ex)
}
......
}

Note: In the dotted part we declare and add various components of Swing; in this part the JDBC code is also used to get an Emp name from the database table that can used in JComboBox. The full code I'll show you below here; I'll only summarize for you what I can do.

D. Add a ActionListener

Add a ActionListener for the button clicked event as in the following:

public void actionPerformed(ActionEvent e) {

                   showData();
            }

Note: If we have multiple buttons then we can use " if (e.getSource() == buttonName) ". But in this app I can use only a single button " Submit " so there is no need to use "e.getSource". I used a method " showData() ". In that method I wrote new frame code.

E. Create a new Frame

Create a new Frame in the showData() method as in the following:
public void showData() {
.........
try{
//JDBC CODE
}Catch(Exception ex)
{
System.out.println(ex)
}
.........
}

F. Create a main method and run the constructor

Finally, create a main method and run the constructor as in the following:

public static void main(String arr[]) {

        new EmpSearchApp();
    }

2. ojdbc.jar file

This JAR file provides a way to set up a Java connection with an Oracle Database. Since the JDBC connection is provided by the Oracle Server vendor we need to import this JAR file in our library folder.

3. NetBeans IDE

This IDE is used to create this application. Since we have a choice we can simply create this app with any text editor, like Notepad, Notepad++, etcetera. But by using NetBeans we can create the Frame and add components like "button", "label", etcetera directly without writing its code. I explained the advantages of the IDE in my previous article "Advantages Of Netbeans IDE" through which you can see the difference.

4. emp.sql table

For fetching records we need a database table; for that we create an "emp" table in our "freeman" database.

Syntax

emp.sql

create table emp
 (
    uname varchar2(20), umail varchar2(30),
    upass varchar2(20), ucountry varchar2(20)
 );

Insert some rows into it as in the following:

1. insert into emp values ('freeman', 'test@tt.com', 'welcome', 'Iran');

2. insert into emp values ('sam', 'sam@ss.com' , '555', 'USA');

Now let's start creating this app. Use the following procedure to do that in the NetBeans IDE.

Step 1

Open the NetBeans IDE.

Step 2

Choose "Java" -> "Java application" as shown below.

Step 3

Provide "EmpSearchApp" for your project name as in the following and click on "Finish".

Step 4

Create a new Java Class "EmpSearchApp" with the following.

EmpSearchApp.java

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.sql.*;

import java.util.Vector;



public class EmpSearchApp extends JFrame implements ActionListener {



    JLabel l, l1, l2, l3, l4, l5;

    JButton b;

    JTextField tf1, tf2, tf3, tf4;

    JComboBox bx;

    String str;



    EmpSearchApp() {

        setVisible(true);

        setSize(700, 700);

        setLayout(null);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setTitle("JDBC DEMO");



        l = new JLabel("Select Name:");

        b = new JButton("Submit");



        tf1 = new JTextField();

        tf2 = new JTextField();

        tf3 = new JTextField();

        tf4 = new JTextField();



        l.setBounds(20, 20, 200, 20);

        b.setBounds(50, 50, 150, 30);



        add(l);

        add(b);



        tf1.setEditable(false);

        tf2.setEditable(false);

        tf3.setEditable(false);

        tf4.setEditable(false);

        b.addActionListener(this);



        try {

            Class.forName("oracle.jdbc.driver.OracleDriver");

            Connection con = DriverManager.getConnection("jdbc:oracle:thin:@mcndesktop07:1521:xe", "freeman", "welcome");

            PreparedStatement ps = con.prepareStatement("select uname from emp");

            ResultSet rs = ps.executeQuery();

            Vector v = new Vector();

            while (rs.next()) {

                String s = rs.getString(1);



                v.add(s);

            }

            bx = new JComboBox(v);

            bx.setBounds(240, 20, 200, 20);

            add(bx);



        } catch (Exception ex) {

            System.out.println(ex);

        }



    }



    public void actionPerformed(ActionEvent e) {

        showData();

    }



    public void showData() {

        JFrame f1 = new JFrame();

        f1.setVisible(true);

        f1.setSize(500, 500);

        f1.setLayout(null);

        f1.setTitle("JDBC DEMO");



        l5 = new JLabel("Displaying Emp Data:");       

        l5.setForeground(Color.red);

        l5.setFont(new Font("Serif", Font.BOLD, 20));

        l1 = new JLabel("Emp Name:");

        l2 = new JLabel("Emp Email:");

        l3 = new JLabel("Emp pass:");

        l4 = new JLabel("Emp Country:");



        l5.setBounds(100, 50, 300, 30);

        l1.setBounds(20, 110, 200, 20);

        l2.setBounds(20, 140, 200, 20);

        l3.setBounds(20, 170, 200, 20);

        l4.setBounds(20, 200, 200, 20);



        tf1.setBounds(240, 110, 200, 20);

        tf2.setBounds(240, 140, 200, 20);

        tf3.setBounds(240, 170, 200, 20);

        tf4.setBounds(240, 200, 200, 20);



        f1.add(l5);

        f1.add(l1);

        f1.add(tf1);

        f1.add(l2);

        f1.add(tf2);

        f1.add(l3);

        f1.add(tf3);

        f1.add(l4);

        f1.add(tf4);



        str = (String) bx.getSelectedItem();

        try {

            Class.forName("oracle.jdbc.driver.OracleDriver");

            Connection con = DriverManager.getConnection("jdbc:oracle:thin:@mcndesktop07:1521:xe", "freeman", "welcome");

            PreparedStatement ps = con.prepareStatement("select * from emp where uname=?");

            ps.setString(1, str);

            ResultSet rs = ps.executeQuery();

            while (rs.next()) {



                tf1.setText(rs.getString(1));

                tf2.setText(rs.getString(2));

                tf3.setText(rs.getString(3));

                tf4.setText(rs.getString(4));



            }

        } catch (Exception ex) {

            System.out.println(ex);

        }

    }



    public static void main(String arr[]) {

        new EmpSearchApp();

    }
}

Step 5

Now your project is ready to run.

Right-click on the project menu and choose "Run". The following output is generated.

Good luck

Answer 2

List<String> foodNames = new ArrayList<>();
ResultSet rs = this.connection.createStatement().executeQuery("SELECT Name FROM Food");
while (rs.next())
{
    foodNames.add(rs.getString(1));
}

Now you've got a list foodNames with all names from all the foods.

You could implement the code like this, where the method "btnFoodActionPerformed(ActionEvent)" is called when you press the button "Food".

private void btnFoodActionPerformed(java.awt.event.ActionEvent evt)
{
    List<String> foodNames = new ArrayList<>();
    ResultSet rs = this.connection.createStatement().executeQuery("SELECT Name FROM Food");
    while (rs.next())
    {
        foodNames.add(rs.getString(1));
    }
//do some stuff with the list
}