java代码实现 线程池监听队列，启动下载线程，下载数据并保存导文件目录，同时更新mysql相应的请求，填充下载文件字段

好的，下面是Java代码实现：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DownloadThreadPool {
    private ExecutorService executorService;
    private LinkedBlockingQueue<DownloadTask> downloadQueue;

    public DownloadThreadPool(int threadPoolSize) {
        executorService = Executors.newFixedThreadPool(threadPoolSize);
        downloadQueue = new LinkedBlockingQueue<>();
    }

    public void addDownloadTask(DownloadTask task) {
        // 存储到 MySQL 数据库
        saveToMysql(task);
        // 将任务添加到队列中
        downloadQueue.offer(task);
    }

    public void start() {
        // 启动线程池监听队列
        executorService.submit(new DownloadRunnable(downloadQueue));
    }

    private void saveToMysql(DownloadTask task) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            // 加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            String url = "jdbc:mysql://localhost:3306/test";
            String username = "root";
            String password = "123456";
            conn = DriverManager.getConnection(url, username, password);
            // 执行 SQL
            String sql = "UPDATE download SET download_file = ? WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, task.getFilename());
            pstmt.setInt(2, task.getId());
            pstmt.executeUpdate();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭数据库连接
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

class DownloadTask {
    private int id;
    private String url;
    private String filename;

    public DownloadTask(int id, String url, String filename) {
        this.id = id;
        this.url = url;
        this.filename = filename;
    }

    public int getId() {
        return id;
    }

    public String getUrl() {
        return url;
    }

    public String getFilename() {
        return filename;
    }
}

class DownloadRunnable implements Runnable {
    private LinkedBlockingQueue<DownloadTask> downloadQueue;

    public DownloadRunnable(LinkedBlockingQueue<DownloadTask> downloadQueue) {
        this.downloadQueue = downloadQueue;
    }

    @Override
    public void run() {
        while (!Thread.currentThread().isInterrupted()) {
            try {
                DownloadTask task = downloadQueue.take();
                // 下载数据并保存到文件目录
                downloadAndSave(task);
                // 更新 MySQL 数据库
                saveToMysql(task);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }

    private void downloadAndSave(DownloadTask task) {
        HttpURLConnection conn = null;
        InputStream inputStream = null;
        FileOutputStream outputStream = null;
        try {
            // 创建 URL 对象
            URL url = new URL(task.getUrl());
            // 打开连接
            conn = (HttpURLConnection) url.openConnection();
            // 设置请求方法
            conn.setRequestMethod("GET");
            // 设置连接超时时间
            conn.setConnectTimeout(5000);
            // 设置读取超时时间
            conn.setReadTimeout(5000);
            // 建立连接
            conn.connect();
            // 获取输入流
            inputStream = conn.getInputStream();
            // 创建文件输出流
            outputStream = new FileOutputStream(task.getFilename());
            // 缓存数组
            byte[] buffer = new byte[1024];
            // 读取长度
            int len;
            // 循环读取数据并写入文件
            while ((len = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, len);
            }
            outputStream.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭连接和流
            try {
                if (outputStream != null) {
                    outputStream.close();
                }
                if (inputStream != null) {
                    inputStream.close();
                }
                if (conn != null) {
                    conn.disconnect();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    private void saveToMysql(DownloadTask task) {
        Connection conn = null;
        PreparedStatement pstmt = null;
        try {
            // 加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
            // 获取数据库连接
            String url = "jdbc:mysql://localhost:3306/test";
            String username = "root";
            String password = "123456";
            conn = DriverManager.getConnection(url, username, password);
            // 执行 SQL
            String sql = "UPDATE download SET download_file = ? WHERE id = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, task.getFilename());
            pstmt.setInt(2, task.getId());
            pstmt.executeUpdate();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭数据库连接
            try {
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

以上代码实现了一个下载线程池及队列，其中`DownloadTask`表示下载任务，包含任务ID、要下载的URL和文件名；`DownloadRunnable`表示下载线程，从队列中取出任务并执行下载操作，下载完成后更新MySQL数据库；`DownloadThreadPool`表示下载线程池，负责接收用户请求，存储到MySQL数据库，将任务添加到队列中并启动下载线程池监听队列。