为什么此代码无法达到从数据库的备份副本还原Derby数据库的目的？

Question

我有一个JavaFXML应用程序，可以访问嵌入式Derby数据库。数据库存储在此文件子系统中：

目录db包含通常的Derby文件和目录：

图1中的备份目录是用户可以从应用程序GUI创建的db的副本。例如：

我想要实现的是能够从GUI中选择一个备份文件，并替换db中包含的当前数据库。我已通过手动删除db并将其替换为备份来验证了这些备份的完整性。

尝试达到目的的代码是：

public class NdBkp 
{
  private static Connection conn = null; 
  public final static String SETUP_FILE_PATH = "/AppData/Local/NewdawnTest_old/"; 
  public static final String CONNECTION_URL = "jdbc:derby:" + "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "db";
  public static final String BACKUP_FILE_PATH = "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "Backups";

  public static void connect() {
    try {  
//      conn = DriverManager.getConnection(CONNECTION_URL  + ";create=true");
      conn = DriverManager.getConnection(CONNECTION_URL);   
    }
    catch (SQLException e) {
      e.printStackTrace();
    } 
  } 

  public static void commit(){
    try {
      conn.commit();
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

  public static boolean isConnected() {
    try{  
      System.out.println("");
      return (!(conn.isClosed()));
    }
    catch (SQLException | NullPointerException e){ 
      e.printStackTrace();
      return false;
    }
  }

  public static void disconnect() {
    try {
      if (conn != null) {
        conn.close();
        conn = null;
      }
    } catch (SQLException e) {
       e.printStackTrace();
    }
  }

  public static void backUpDatabase(String dirname) {
    try {
      CallableStatement cs = conn.prepareCall("CALL SYSCS_UTIL.SYSCS_BACKUP_DATABASE(?)");
      cs.setString(1, BACKUP_FILE_PATH + "/" + dirname);
      cs.execute();
      cs.close();
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

  public static void restoreDatabase(String backupdirpath) {
    System.out.println("Restoring " + CONNECTION_URL + " from + " + backupdirpath);
    try {
      DriverManager.getConnection(CONNECTION_URL + ";restoreFrom=backupdirpath");
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

  public static void main (String [] args)
  {
    String backupdirpath = "C:/Users/Administrator/AppData/Local/NewdawnTest_old/Backups/20200515_bkp_02";
    connect(); 
    restoreDatabase(backupdirpath);
    System.out.println("Is connected is " + isConnected());
    disconnect();
    System.out.println("Is connected is " + isConnected());
 }
}

当我编译并运行此代码时，一切似乎正常。没有错误转储，也没有任何迹象表明restoreDatabase方法中定义的请求的操作无效。但是，当我查看文件系统时，实际上什么都没有发生，db的当前版本仍然不受影响。我不知道为什么会这样，也不知道缺少什么，因此，我将为您提供一些帮助。

Answer 1

问题可能是，您只是在应添加此名称引用的变量值的位置附加单词“ backupdirpath”？

  public static void restoreDatabase(String backupdirpath) {
    System.out.println("Restoring " + CONNECTION_URL + " from + " + backupdirpath);
    try {
      // I think this:
      DriverManager.getConnection(CONNECTION_URL + ";restoreFrom=backupdirpath");
      // should be this:
      //DriverManager.getConnection(CONNECTION_URL + ";restoreFrom=" + backupdirpath);
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

Answer 2

尝试使用此代码以最小化行并发现错误：

public class Restore {

  public void restoreDatabaseRoutine() {

          String restoreUrl = "jdbc:derby:Test;restoreFrom=/path/to/another/db";
          String driver = "org.apache.derby.jdbc.EmbeddedDriver";
          Class.forName(driver);
          Connection conn = DriverManager.getConnection(restoreUrl);
          conn.close();
          System.out.println("The database has been successfully restored");
  }
}