在Windows计算机上为Derby Embedded数据库调用shutdown = true时，我无法删除system directory。
下面是我面临挑战的一个最小例子：

package derbytest;

import java.io.File;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author aelder
 */
public class DerbyTest {

    private static final String DRIVER = "org.apache.derby.jdbc.EmbeddedDriver";
    private static final String CONN_URL = "jdbc:derby:EmbeddedDBAudit";

    private static File derbySystemFolder;
    private static final String USER_HOME_DIR = System.getProperty("user.home", ".");

    public static Connection getConnection(boolean createDatabase) throws SQLException {
        return DriverManager.getConnection(CONN_URL + (createDatabase ? ";create=true" : ""));
    }

    public static void shutdownConnectionAndCleanup() {
        try {
            DriverManager.getConnection(CONN_URL + ";shutdown=true");
        } catch (SQLException ex) {
            if (!ex.getSQLState().equals("08006")) {
                ex.printStackTrace();
            }
        }

        deleteFolder(derbySystemFolder);
    }

    public static void deleteFolder(File folder) {
        File[] files = folder.listFiles();
        if (files != null) { //some JVMs return null for empty dirs
            for (File f : files) {
                if (f.isDirectory()) {
                    deleteFolder(f);
                } else {
                    f.delete();
                }
            }
        }
        folder.delete();
    }

    public static void setDerbyHome() {
        setDatabaseFile("");

        int index = 1;
        while (derbySystemFolder.exists()) {
            setDatabaseFile(String.valueOf(index++));
        }

        // Set the db system directory.
        System.setProperty("derby.system.home", derbySystemFolder.getAbsolutePath());
    }

    private static void setDatabaseFile(String auditFolderCount) {
        String databaseFilePATH = USER_HOME_DIR + File.separator + ".EmbeddedDBAudit" + auditFolderCount;

        derbySystemFolder = new File(databaseFilePATH);
        derbySystemFolder.deleteOnExit();
    }

    public static void initDerbyHomeAndDriver() {
        setDerbyHome();

        initDerbyDriverInstance();
    }

    public static void initDerbyDriverInstance() {
        try {
            Class.forName(DRIVER).newInstance();
        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException ex) {
            Logger.getLogger(DerbyTest.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static boolean tableAlreadyExists(SQLException e) {
        return e.getSQLState().equals("X0Y32");
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {
            initDerbyHomeAndDriver();
            getConnection(true);
            shutdownConnectionAndCleanup();
        } catch (SQLException ex) {
            Logger.getLogger(DerbyTest.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

我也试过使用外部库来删除文件夹，比如apache的org.apache.commons.io.FileDeleteStrategy.FORCE.delete(file);或import org.apache.commons.io.FileUtils.deleteDirectory(file);，看起来derby系统在数据库关闭后仍然挂起文件。
预期行为：退出时删除system directory。
编辑：
Windows进程资源管理器显示，在关闭数据库连接后，derby.log仍处于打开状态：