设计一个基于Java swing和MySQL的分类查询功能代码

好的，以下是一个简单的Java Swing和MySQL分类查询代码示例：

import java.sql.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class CategoryQuery extends JFrame {

    private JPanel contentPane;
    private JTextField searchField;
    private JComboBox<String> categoryComboBox;
    private JTextArea resultArea;
    private Connection conn;

    public CategoryQuery() {
        // 设置窗口标题
        setTitle("分类查询");

        try {
            // 加载MySQL驱动
            Class.forName("com.mysql.jdbc.Driver");
            // 连接MySQL数据库
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "password");
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }

        // 设置窗口大小
        setSize(500, 400);
        // 居中显示窗口
        setLocationRelativeTo(null);
        // 关闭窗口时退出程序
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // 创建内容面板
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        // 创建查询面板
        JPanel queryPanel = new JPanel();
        contentPane.add(queryPanel, BorderLayout.NORTH);

        JLabel categoryLabel = new JLabel("分类:");
        queryPanel.add(categoryLabel);

        // 创建分类下拉框
        categoryComboBox = new JComboBox<String>();
        queryPanel.add(categoryComboBox);

        try {
            // 查询分类数据
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT DISTINCT category FROM products");
            while (rs.next()) {
                categoryComboBox.addItem(rs.getString("category"));
            }
            rs.close();
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        JLabel searchLabel = new JLabel("关键字:");
        queryPanel.add(searchLabel);

        // 创建搜索框
        searchField = new JTextField();
        queryPanel.add(searchField);
        searchField.setColumns(20);

        // 创建查询按钮
        JButton queryButton = new JButton("查询");
        queryButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // 获取用户选择的分类和搜索关键字
                String category = (String) categoryComboBox.getSelectedItem();
                String keyword = searchField.getText().trim();

                try {
                    // 查询数据
                    Statement stmt = conn.createStatement();
                    ResultSet rs = stmt.executeQuery("SELECT name, price FROM products WHERE category = '" + category + "' AND name LIKE '%" + keyword + "%'");
                    StringBuilder sb = new StringBuilder();
                    while (rs.next()) {
                        sb.append(rs.getString("name")).append("\t").append(rs.getDouble("price")).append("\n");
                    }
                    rs.close();
                    stmt.close();

                    // 显示查询结果
                    resultArea.setText(sb.toString());
                } catch (SQLException ex) {
                    ex.printStackTrace();
                }
            }
        });
        queryPanel.add(queryButton);

        // 创建结果面板
        JPanel resultPanel = new JPanel();
        contentPane.add(resultPanel, BorderLayout.CENTER);
        resultPanel.setLayout(new BorderLayout(0, 0));

        JLabel resultLabel = new JLabel("查询结果:");
        resultPanel.add(resultLabel, BorderLayout.NORTH);

        // 创建结果文本框
        resultArea = new JTextArea();
        resultPanel.add(resultArea, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        CategoryQuery frame = new CategoryQuery();
        frame.setVisible(true);
    }

}

这个程序包括一个查询面板和一个结果面板。查询面板中包括一个分类下拉框、一个搜索框和一个查询按钮，用户可以选择分类并输入关键字进行查询。结果面板中显示查询结果。程序使用了MySQL数据库，需要事先在本地安装和配置好MySQL。