java - 如何在java中动态连接mysql数据库并显示所选数据库的表、属性？

Question

我使用的是 mysql 5.7，我创建了一些数据库。我在 netbeans ide 8.2 中使用下拉菜单 [JComboBox] 显示它们

数据库

+--------------------
| classicmodels
| db1
| db2

以下内容为必填内容

当选择 db1(可以选择任何显示值)时，我想与其建立连接。然后在窗口中显示表格以及窗口中每个表格下的属性/列。

数据库.java

import java.sql.*;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

public class Database extends javax.swing.JFrame {
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;

    /**
     * Creates new form Database
     */
    public Database() {
        initComponents();
        java.util.ArrayList<String> tables = new ArrayList<>();
        conn = MySqlConnect.ConnectDB();
        String sql = "show databases;";
        try {
            stmt = conn.createStatement();
            stmt.execute(sql);
            rs = stmt.getResultSet();
            while (rs.next()) {
                jComboBox1.addItem(rs.getString("Database"));
            }

        } catch (SQLException ex) {
            Logger.getLogger(Database.class.getName()).log(Level.SEVERE, null, ex);
        }

        if (null != selection) {
            selection.setVisible(false);
        }

    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        jMenuItem1 = new javax.swing.JMenuItem();
        jMenuItem2 = new javax.swing.JMenuItem();
        jMenuItem3 = new javax.swing.JMenuItem();
        jComboBox1 = new javax.swing.JComboBox<>();

        jMenuItem1.setText("jMenuItem1");

        jMenuItem2.setText("jMenuItem2");

        jMenuItem3.setText("jMenuItem3");

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Available DataSources");
        setFont(new java.awt.Font("Arial", 0, 12)); // NOI18N
        setForeground(new java.awt.Color(51, 0, 255));

        jComboBox1.addItemListener(new java.awt.event.ItemListener() {
            public void itemStateChanged(java.awt.event.ItemEvent evt) {
                jComboBox1ItemStateChanged(evt);
            }
        });
        jComboBox1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jComboBox1ActionPerformed(evt);
            }
        });
        jComboBox1.addKeyListener(new java.awt.event.KeyAdapter() {
            public void keyPressed(java.awt.event.KeyEvent evt) {
                jComboBox1KeyPressed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup().addGap(159, 159, 159)
                        .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE,
                                javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(213, Short.MAX_VALUE)));
        layout.setVerticalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup().addGap(92, 92, 92)
                        .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE,
                                javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(401, Short.MAX_VALUE)));

        setBounds(0, 0, 416, 552);
    }// </editor-fold>

    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        selection = new QueryPredictor(jComboBox1.getSelectedItem().toString());
        selection.setVisible(true);

    }

    private void jComboBox1KeyPressed(java.awt.event.KeyEvent evt) {
        // TODO add your handling code here:
    }

    private void jComboBox1ItemStateChanged(java.awt.event.ItemEvent evt) {
        // TODO add your handling code here:
    }

    /**
     * @param args
     *            the command line arguments
     */
    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(Database.class.getName()).log(java.util.logging.Level.SEVERE,
                    null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Database.class.getName()).log(java.util.logging.Level.SEVERE,
                    null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Database.class.getName()).log(java.util.logging.Level.SEVERE,
                    null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Database.class.getName()).log(java.util.logging.Level.SEVERE,
                    null, ex);
        }
        // </editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Database().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify
    private javax.swing.JComboBox<String> jComboBox1;
    private javax.swing.JMenuItem jMenuItem1;
    private javax.swing.JMenuItem jMenuItem2;
    private javax.swing.JMenuItem jMenuItem3;
    // End of variables declaration
}

MySqlConnect.java

import java.sql.*;
import javax.swing.JOptionPane;

public class MySqlConnect {
    Connection conn = null;

    public static Connection ConnectDB() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/classicmodels", "root", "system");
                                                          //"jdbc:mysql://localhost:3306/db1","root","system");
                                                          //"jdbc:mysql://localhost:3306/db2","root","system");         

            return conn;

        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, e);
            return null;
        }
    }

}

Answer 1

为 public static Connection ConnectDB() 传递参数如public static Connection ConnectDB(String db)

然后

Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+db, "root", "system");

使用有效的数据库名称在构造函数中调用 Connection 类。例如:conn = MySqlConnect.ConnectDB(classicmodels);

然后是jComboBox1ActionPerformed事件再次使用连接作为 conn = MySqlConnect.ConnectDB(jComboBox1.getSelectedItem().toString);

然后您可以使用选定的数据库进行表填充。