Question

我开始使用Java学习SQL，我正在尝试使用Swing和SQLite创建注册/登录系统。

所以，我几乎完整的基本登录系统，但我被卡住了。我有一个名为user的表，我有2个带按钮的文本字段，如果点击了按钮，它只是说你好+＆＃39;用户名＆＃39;。所以在我的表中，例如，我有2个值：

例如，我有表＆＃39;用户＆＃39;：

+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| admin    | varchar(255) | YES  |     | NULL    |       |
| password | varchar(255) | YES  |     | NULL    |       |
+----------+--------------+------+-----+---------+-------+

有数据：

+----------+-------------+
| admin    | password    |
+----------+-------------+
| myLogin  | myPassword  |
| myLogin1 | myPassword1 |
+----------+-------------+

当我输入myUsername1，myPassword1等时，它才会识别它。如果我输入myUsername，myPassword

，它将无法识别

所以基本上我试图弄清楚如何检查用户输入的例子管理员密码而不是问你好管理员等。

所以这是我的Connect.java

import java.sql.*;

import javax.swing.JOptionPane; 

public class Connect {

static String username;
static String password;
static String query;

public static Connection ConnectDB() {
    try {

        Class.forName("org.sqlite.JDBC");
        Connection conn = null;
        conn = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\Alex\\workspace   \\RegisterAndLoginSystem\\System.sqlite");

        Statement state = null;
        state = conn.createStatement();

        query = "SELECT * FROM `user`";
        // This query does not work as well
        // query = "SELECT admin,password FROM user WHERE admin = '" + GuiLogin.user + "' AND password = '" + GuiLogin.pass + "'";


        ResultSet rs = state.executeQuery(query);

        while(rs.next()) {
            username = rs.getString("admin");
            System.out.println(username);
            password = rs.getString("password");
            System.out.println(password);
        }
        rs.close();
        state.close();

        return conn;

    } catch(Exception e) {
        JOptionPane.showMessageDialog(null, "Could not connect: " + e);
        return null;
    }
}

}

例如现在我可以输入admin1 password1而不是它会验证但是我有太多的管理员密码我无法验证。

这是我的GUI类：

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

    import javax.swing.*;

    public class GuiLogin extends JFrame {

    public static final long serialVersionUID = 1L;

    private JPanel panel;
    private JButton button;
    private JTextField field1;
    private JPasswordField field2;
    private JLabel label1, label2, answer;

    static String user;
    static String pass;

    public GuiLogin() {

        try {
             UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch(Exception e) {
            e.printStackTrace();
        }

        panel = new JPanel();

        label1 = new JLabel("Username:");
        panel.add(label1);

        field1 = new JTextField("", 15);
        panel.add(field1);

        label2 = new JLabel("Password:");
        panel.add(label2);

        field2 = new JPasswordField("", 15);
        panel.add(field2);

        button = new JButton("Login");
        button.setFocusPainted(false);
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if(e.getSource() == button) {
                    user = field1.getText();
                    pass = field2.getText();

                    if(user.equals(Connect.username) && pass.equals(Connect.password)) {
                        answer.setText("Logged in");
                    } else {
                        answer.setText("Bad login data try again");
                    }
                }
            }
        });
        panel.add(button);

        answer = new JLabel("");
        panel.add(answer);

        this.add(panel);
        this.setSize(500, 400);
        this.setVisible(true);
        this.setResizable(false);
        this.setLocationRelativeTo(null);
        this.setTitle("Login");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        Connect.ConnectDB();
        new GuiLogin();
    }

    }

任何帮助都会很棒！

Answer 1

你应该将ConnectDB调用到ActionPerformed方法，因为在你加载GUI之前，你的代码数据是来自数据库的，所以在用户输入他的名字和密码后点击来自DB的数据并点击＆＃34;登录＆＃34;按钮。

重写GUI类：

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class GuiLogin extends JFrame {

    public static final long serialVersionUID = 1L;

    private JPanel panel;
    private JButton button;
    private JTextField field1;
    private JPasswordField field2;
    private JLabel label1, label2, answer;

    static String user;
    static String pass;

    public GuiLogin() {

        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e) {
            e.printStackTrace();
        }

        panel = new JPanel();

        label1 = new JLabel("Username:");
        panel.add(label1);

        field1 = new JTextField("", 15);
        panel.add(field1);

        label2 = new JLabel("Password:");
        panel.add(label2);

        field2 = new JPasswordField("", 15);
        panel.add(field2);

        button = new JButton("Login");
        button.setFocusPainted(false);
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (e.getSource() == button) {
                    user = field1.getText();
                    pass = field2.getText();

                    Connect.ConnectDB();

                    if (user.equals(Connect.username)
                            && pass.equals(Connect.password)) {
                        answer.setText("Logged in");
                    } else {
                        answer.setText("Bad login data try again");
                    }
                }
            }
        });
        panel.add(button);

        answer = new JLabel("");
        panel.add(answer);

        this.add(panel);
        this.setSize(500, 400);
        this.setVisible(true);
        this.setResizable(false);
        this.setLocationRelativeTo(null);
        this.setTitle("Login");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        new GuiLogin();
    }
}

现在评论的SQL查询将起作用。所以使用查询：

query = "SELECT admin,password FROM user WHERE admin = '" + GuiLogin.user + "' AND password = '" + GuiLogin.pass + "'";

如何使用JDBC基于多个条件过滤数据库记录？

1 个答案: