查询并把查询结果显示Jframe上的代码

查询数据库并在 JFrame 上显示结果的代码示例如下：

import java.awt.BorderLayout;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;

public class DatabaseTable extends JFrame {

    private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "password";

    private Connection conn = null;
    private Statement stmt = null;
    private ResultSet rs = null;

    private JTable table;

    public DatabaseTable() {
        try {
            // Register JDBC driver
            Class.forName(JDBC_DRIVER);

            // Open a connection
            conn = DriverManager.getConnection(DB_URL, USERNAME, PASSWORD);

            // Execute query
            stmt = conn.createStatement();
            String sql = "SELECT * FROM mytable";
            rs = stmt.executeQuery(sql);

            // Create JTable with ResultSet
            table = new JTable(buildTableModel(rs));

            // Add JTable to JFrame
            JScrollPane scrollPane = new JScrollPane(table);
            getContentPane().add(scrollPane, BorderLayout.CENTER);

            // Set frame properties
            setTitle("Database Table");
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            setSize(600, 400);
            setLocationRelativeTo(null);
            setVisible(true);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                // Close ResultSet, Statement, Connection
                rs.close();
                stmt.close();
                conn.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

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

    // Helper method to build JTable from ResultSet
    public static JTable buildTableModel(ResultSet rs) {
        try {
            // Get metadata of ResultSet
            int columnCount = rs.getMetaData().getColumnCount();

            // Create array of column names
            String[] columnNames = new String[columnCount];
            for (int i = 1; i <= columnCount; i++) {
                columnNames[i-1] = rs.getMetaData().getColumnName(i);
            }

            // Create array of row data
            Object[][] rowData = new Object[0][columnCount];
            while (rs.next()) {
                Object[] newRow = new Object[columnCount];
                for (int i = 1; i <= columnCount; i++) {
                    newRow[i-1] = rs.getObject(i);
                }
                rowData = addRow(rowData, newRow);
            }

            // Create JTable with column names and row data
            JTable table = new JTable(rowData, columnNames);
            return table;

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    // Helper method to add row to array of row data
    public static Object[][] addRow(Object[][] rowData, Object[] newRow) {
        Object[][] result = new Object[rowData.length + 1][];
        System.arraycopy(rowData, 0, result, 0, rowData.length);
        result[rowData.length] = newRow;
        return result;
    }

}

在这个示例中，我们使用了 MySQL 数据库，并从一个名为 `mytable` 的表中检索了所有数据。然后，我们将结果集用 `buildTableModel()` 方法转换为 JTable，并将其添加到 JFrame 中显示。最后，我们关闭了结果集、语句和连接。你可以根据自己的需要进行修改。