如何使用JDBC基於多個條件過濾數據庫記錄？

Question

我開始使用Java學習SQL，並試圖使用Swing和SQLite進行註冊/登錄系統。

所以，我做了幾乎整個基本的登錄系統，但我堅持。我有名爲user的表格，我有兩個帶有按鈕的文本字段，如果點擊了按鈕，它只是表示hello +'username'。所以在我的表，例如，我有2個值：

例如，我有表 '用戶'：

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

數據：

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

這將只是承認，當我輸入myUsername1，myPassword1等。它不會識別，如果我輸入myUsername，我的密碼

所以基本上我想弄清楚如何檢查用戶輸入例如只是 管理員密碼 比打招呼管理等

因此，這裏是我的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; 
    } 
} 

} 

比如現在就可以進入ADMIN1密碼1，只是比它會驗證，但我有太多的管理員密碼這我無法驗證。

這裏是我的GUI類：

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(); 
    } 

    } 

任何幫助將是巨大的！

Answer 1

您應該將ConnectDB調用到ActionPerformed方法中，因爲在您的代碼中，數據庫中的數據是在加載GUI之前獲得的，而用戶輸入其名稱和密碼後，應該加載數據庫中的數據並單擊「登錄」按鈕。

重寫GUI類這樣的：即評論將工作

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(); 
    } 
} 

現在SQL查詢。因此，請使用查詢：

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