如何使用JDBC基于多个条件过滤数据库记录？

Question

我开始使用Java学习SQL，并试图使用Swing和SQLite进行注册/登录系统。

所以，我做了几乎整个基本的登录系统，但我坚持。我有名为user的表格，我有两个带有按钮的文本字段，如果点击了按钮，它只是表示hello +'username'。所以在我的表，例如，我有2个值：

例如，我有表 '用户'：

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

数据：

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

这将只是承认，当我输入myUsername1，myPassword1等。它不会识别，如果我输入myUsername，我的密码

所以基本上我想弄清楚如何检查用户输入例如只是 管理员密码 比打招呼管理等

因此，这里是我的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; 
    } 
} 

} 

比如现在就可以进入ADMIN1密码1，只是比它会验证，但我有太多的管理员密码这我无法验证。

这里是我的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(); 
    } 

    } 

任何帮助将是巨大的！

Answer 1

您应该将ConnectDB调用到ActionPerformed方法中，因为在您的代码中，数据库中的数据是在加载GUI之前获得的，而用户输入其名称和密码后，应该加载数据库中的数据并单击“登录”按钮。

重写GUI类这样的：即评论将工作

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(); 
    } 
} 

现在SQL查询。因此，请使用查询：

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