Из-за чего ошибка java.lang.ClassNotFoundException: com.mysql.jdbc.Driver?

Question

[alzhovtyak]

Полный текст вывода в консоль:
дек. 12, 2020 6:28:40 PM course.UserLogin$2 actionPerformed
SEVERE: null
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:315)
at course.UserLogin$2.actionPerformed(UserLogin.java:113)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6631)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6396)
at java.desktop/java.awt.Container.processEvent(Container.java:2263)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5007)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4839)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4839)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Исходный код:

package course;

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;

public class UserLogin extends JFrame {

    private static final long serialVersionUID = 1L;
    private JTextField textField;
    private JPasswordField passwordField;
    private JButton btnNewButton;
    private JLabel label;
    private JPanel contentPane;
    private static final String sqlurl = "jdbc:mysql://localhost:3306/mycoursework";
    private static final String sqlname = "root";
    private static final String sqlpassword = "1112"; 
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    UserLogin frame = new UserLogin();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public UserLogin() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(450, 190, 1014, 597);
        setResizable(false);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        contentPane.setLayout(null);

        JLabel lblNewLabel = new JLabel("Login");
        lblNewLabel.setForeground(Color.BLACK);
        lblNewLabel.setFont(new Font("Times New Roman", Font.PLAIN, 46));
        lblNewLabel.setBounds(423, 13, 273, 93);
        contentPane.add(lblNewLabel);

        textField = new JTextField();
        textField.setFont(new Font("Tahoma", Font.PLAIN, 32));
        textField.setBounds(481, 170, 281, 68);
        contentPane.add(textField);
        textField.setColumns(10);

        passwordField = new JPasswordField();
        passwordField.setFont(new Font("Tahoma", Font.PLAIN, 32));
        passwordField.setBounds(481, 286, 281, 68);
        contentPane.add(passwordField);

        JLabel lblUsername = new JLabel("Username");
        lblUsername.setBackground(Color.BLACK);
        lblUsername.setForeground(Color.BLACK);
        lblUsername.setFont(new Font("Tahoma", Font.PLAIN, 31));
        lblUsername.setBounds(250, 166, 193, 52);
        contentPane.add(lblUsername);

        JLabel lblPassword = new JLabel("Password");
        lblPassword.setForeground(Color.BLACK);
        lblPassword.setBackground(Color.CYAN);
        lblPassword.setFont(new Font("Tahoma", Font.PLAIN, 31));
        lblPassword.setBounds(250, 286, 193, 52);
        contentPane.add(lblPassword);

        btnNewButton = new JButton("Login");
        btnNewButton.setFont(new Font("Tahoma", Font.PLAIN, 26));
        btnNewButton.setBounds(545, 392, 162, 73);
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String userName = textField.getText();
                String password = passwordField.getText();
                try {                  
                    Class.forName("com.mysql.jdbc.Driver");
                    Connection connection = (Connection) DriverManager.getConnection(sqlurl,
                        sqlname, sqlpassword);

                    PreparedStatement st = (PreparedStatement) connection
                        .prepareStatement("Select name, password from user where name=? and password=?");

                    st.setString(1, userName);
                    st.setString(2, password);
                    ResultSet rs = st.executeQuery();
                    if (rs.next()) {
                        dispose();
                        
                        JOptionPane.showMessageDialog(btnNewButton, "You have successfully logged in");
                    } else {
                        JOptionPane.showMessageDialog(btnNewButton, "Wrong Username & Password");
                    }
                } catch (SQLException sqlException) {
                    sqlException.printStackTrace();
                } catch (ClassNotFoundException ex) {
                    Logger.getLogger(UserLogin.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });

        contentPane.add(btnNewButton);

        label = new JLabel("");
        label.setBounds(0, 0, 1008, 562);
        contentPane.add(label);
    }
}

Comments

[alzhovtyak]

да

[сергей кузьмин]

alzhovtyak, в classpath или в аргументы команды он тоже добавлен ?

Answer 1

[Орхан Гасанлы]

Здравствуйте!
Подозреваю, что драйвер у вас не подключен. Используете ли вы maven или gradle? Если да, то добавьте драйвер согласно документации.
Если вы не используете build tools, то убедитесь доступен ли драйвер в classpath.
Также проверьте установлен ли mysql у вас локально? А то вы пытаетесь подключиться к БД на локалке
jdbc:mysql://localhost:3306/mycoursework
Также попробуйте заменить вот, эту строку:
Class.forName("com.mysql.jdbc.Driver");
на
Class.forName(" com.mysql.cj.jdbc.Driver");