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执行查询[重复]后立即关闭结果集

resultset prepared-statement jdbc sqlite java

Samuel Ludwig · 技术社区 · 8 年前

我使用以下方法在JavaFX应用程序中显示来自数据库的信息

public void showFirstSix() {
    PreparedStatement takeFields = null;
    ResultSet rs = null;
    String sqlTakeFields = "SELECT * FROM VirtualProductTable WHERE VirtualProductTable MATCH name=? ORDER BY rank DESC";
    try {
        takeFields = this.newSearchModel.connection.prepareStatement(sqlTakeFields);
        takeFields.setString(1, nameSearch.getText());
        rs = takeFields.executeQuery();
    } catch (SQLException e1) {
        e1.printStackTrace();
    }

    // gets a sorted list of matching products, next we just need to print them out entry by entry //
    // we'll traverse every row in the result set, and print all needed values before moving to the next row //

    try {

        // first entry
        String id = rs.getString(2);
        String name = rs.getString(3);
        String description = rs.getString(4);
        String price = rs.getString(5);
        String length = rs.getString(6);
        String width = rs.getString(7);
        String height = rs.getString(8);
        String dateAdded = rs.getString(9);
        Blob image = rs.getBlob(14);

        id1.setText(id);
        name1.setText(name);
        description1.setText(description);
        dateAdded1.setText(dateAdded);
        price1.setText(price);
        length1.setText(length);
        width1.setText(width);
        height1.setText(height);
        image1.setImage((Image) image);

        // second entry
        rs.next();

        id = rs.getString(2);
        name = rs.getString(3);
        description = rs.getString(4);
        price = rs.getString(5);
        length = rs.getString(6);
        width = rs.getString(7);
        height = rs.getString(8);
        dateAdded = rs.getString(9);
        image = rs.getBlob(14);

        id2.setText(id);
        name2.setText(name);
        description2.setText(description);
        dateAdded2.setText(dateAdded);
        price2.setText(price);
        length2.setText(length);
        width2.setText(width);
        height2.setText(height);
        image2.setImage((Image) image);

        ...

    } catch (SQLException e1) {
        e1.printStackTrace();
    } 

}

执行此方法后,我在第二个try块中得到一个指向第一个rs.getString()行的错误,声称ResultSet已关闭

我真正的问题似乎发生在第一个try块中,紧接着 rs = takeFields.executeQuery() - 我用一些 System.out.println(rs.isClosed()) 和 System.out.println(takeFields.isClosed()) 在上述查询之后,并确认准备好的语句takeFields实际上仍然处于打开状态,但结果集rs在查询执行后立即关闭。

我在研究类似的问题,我已经确认,这个特定的准备好的语句从未在其他任何地方使用或引用过,也从未关闭过,所以我试图弄清楚为什么这个结果集总是立即关闭,以及如何使其配合。

1 回复 | 直到 8 年前

Adrian 8 年前

典型的处理结果集迭代器使用下一个方法调用,如下所示:

  ResultSet rs = stmt.executeQuery(query);
  while (rs.next()) {

    //read record
  }

在您的情况下,请确保在阅读第一条记录之前拨打next:

  ResultSet rs = stmt.executeQuery(query);
  if(! rs.next()) {
    return;
  }
  //read first reacord

   if(! rs.next()) {
    return;
  }
  //read second reacord