如何将java数据库连接连接到许多jFrames？

Posted 2023-03-27

【中文标题】如何将java数据库连接连接到许多jFrames？

【英文标题】：How to connect java database connection to many jFrames?

【发布时间】：2015-05-04 04:25:34

【问题描述】：

我创建了一个名为DBConnection 的类来连接sql 数据库。我还有一个名为 AdminLogin 的 jFrame。我想知道的是，如何将数据库连接传递给 AdminLogin 类，而无需键入整个数据库连接代码。

这是我的 DBConnection 类

package ltdasystem;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;



public class DBConnection 

    private Connection conn = null;
    private String query = null;
    private ResultSet rs;
    private final String url=("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase");
    private final String usrName = "sa";
    private final String pwd= "p@ssword13";

    public DBConnection() 
        try
            conn = DriverManager.getConnection(url, usrName, pwd);
            query = "SELECT * from UserATable";
            PreparedStatement stm = conn.prepareStatement(query);
            rs = stm.executeQuery();
            while (rs.next())
                String userName = rs.getString("Username");
                String password = rs.getString("Password");

                System.out.println("Username : " + userName + "\n" + "Password : " + password); 

            
            conn.close();

        catch (SQLException e)

          System.out.println(e.getMessage());

        

    

  

这是我的 AdminLogin。我现在做的方法很好，但我想不用输入所有的数据库连接代码。

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.swing.JOptionPane;


/**
 *
 * @author Yasitha
 */
public class AdminLogin extends javax.swing.JFrame 

     Connection conn = null;
     String query = null;
     ResultSet rs;
    private final String url=("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase");
    private final String usrName = "sa";
    private final String pwd= "p@ssword13";


    /**
     * Creates new form AdminLogin
     */
    public AdminLogin() 
        initComponents();
    



    private void LoginButtonActionPerformed(java.awt.event.ActionEvent evt)                                             
        //DBConnection db = new DBConnection();

       try

             conn = DriverManager.getConnection(url, usrName, pwd);
             query = "SELECT * FROM UserATable WHERE Username = '" + userName.getText()
                    + "' AND Password = " + password.getText();


          PreparedStatement stm = conn.prepareStatement(query);
            rs = stm.executeQuery();
            if(rs.next())
                dispose();
                String x = rs.getString("Username");
               AdminMenu admenu = new AdminMenu();
               admenu.setVisible(true);
               admenu.generate(x);

       

       catch (SQLException ex) 

           JOptionPane.showMessageDialog(null, ex);
           //return null;

         finally 


           
                                               


        java.awt.EventQueue.invokeLater(new Runnable() 
            public void run() 
                new AdminLogin().setVisible(true);
            
        );
    

    // Variables declaration - do not modify                     
    private javax.swing.JButton BackButton;
    private javax.swing.JButton LoginButton;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPasswordField password;
    private javax.swing.JTextField userName;
    // End of variables declaration                   

【问题讨论】：

将DBConnection 更改为更像工厂，它提供了您可以请求它代表您进行查询的方法。也使用构造函数为连接属性播种，然后简单地将DBConnection 的实例传递给需要对数据库进行查询的类

【参考方案1】：

改变你的设计。 DBConnection 应该是一个工厂/管理器，它包装了数据库连接和查询的核心功能和管理（或至少形成了基础）

public interface DBConnection 

    public Connection getConnection() throws SQLException;

然后您可以创建查询管理类或方法来处理实际繁重的工作......

public class UserQueryManager 

    public boolean isValidUser(DBConnection dBConnection, String name, String password) throws SQLException 

        boolean isValidUser = false;
        try (Connection con = dBConnection.getConnection()) 

            try (PreparedStatement stmt = con.prepareStatement("select count(*) from UserATable where name=? and password=?")) 

                try (ResultSet rs = stmt.executeQuery()) 

                    if (rs.next()) 

                        int count = rs.getInt(1);
                        isValidUser = count > 0; // Maybe count == 1 would be more valid

                    

                

            

        

        return isValidUser;

    

现在，我们需要实现DBConnection 接口，类似于...

public class DefaultDBConnection implements DBConnection 

    private final String url;
    private final String userName;
    private final String password;

    public DefaultDBConnection(String url, String userName, String password) 
        this.url = url;
        this.userName = userName;
        this.password = password;
    

    @Override
    public Connection getConnection() throws SQLException 

        return DriverManager.getConnection(url, userName, password);

    

然后您将创建DBConnection 的实例...

DefaultDBConnection dBConnection = new DefaultDBConnection("jdbc:sqlserver://localhost:1433;databaseName=LeisureToursDatabase", "sa", "p@ssword13");

并将其传递给您的框架（或任何其他可能喜欢使用它的人）

AdminLogin adminLogin = new AdminLogin(dBConnection);

然后您需要修改AdminLogin 以通过构造函数接受参数...

public class AdminLogin extends javax.swing.JFrame 

    private DBConnection dBConnection;

    /**
     * Creates new form AdminLogin
     */
    public AdminLogin(DBConnection dBConnection) 
        this.dBConnection = dBConnection;
        initComponents();
    

还有LoginButtonActionPerformed 来设置UserQueryManager 并调用isValidUser...

private void LoginButtonActionPerformed(java.awt.event.ActionEvent evt) 
    try 
        UserQueryManager userQuertManager = new UserQueryManager();
        if (userQuertManager.isValidUser(dBConnection, userName.getText(), password.getText())) 
            dispose();
            AdminMenu admenu = new AdminMenu();
            admenu.setVisible(true);
            admenu.generate(userName.getText());
        
     catch (SQLException ex) 
        JOptionPane.showMessageDialog(null, ex);
        //return null;
    

请注意，您确实不应该将密码传递为 Strings，而应该使用 char[] 数组。

另外，您可以考虑看看The Use of Multiple JFrames, Good/Bad Practice? 和How to Use CardLayout

【参考方案2】：

只是想在此处添加一些更改点... isValidUser 可以是静态方法，因为不涉及任何状态。 因此“UserQueryManager userQuertManager = new UserQueryManager()” 每次单击按钮时都会创建新对象...

dbconnection 也可以作为接口注入到 UserQueryManager 成员。 同样对于主要的提问者..如果您以 MVC 的角度看待这些类，那么如果您查看

，代码的分解会更好

AdminLogin 是一个作为 View 组件的框架 ...因此，将 DBConnection 或 QueryManager 对象视为该组件的成员变量不是很干净。