JavaSpringJDBC

我是java和spring的新手，我知道jdbc已經過時了，但我想掌握這項技術，為什么當我使用ResultSet生成請求時，我遇到了問題，我完全不明白發生了什么

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盡管如果您通過控制臺重復相同的請求，則一切正常

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查詢：

private final static String CREATE_CAR_QUERY = "insert into cars values(default,?,?,?,?,?,?,?,?,?)";

private final static String CREATE_DRIVER_CAR_QUERY = "insert into driver_car values(?,?)";

private final static String FIND_CAR_ID_BY_CAR_NUMBER_QUERY = "select id from cars where car_number = ";

功能：

> public void create(Car entity, Long driverId) {
>         Long carId = 0L;
>         try (PreparedStatement preparedStatement = jpaConfig.getConnection().prepareStatement(CREATE_CAR_QUERY)) {
>             preparedStatement.setTimestamp(1, new Timestamp(entity.getCreated().getTime()));
>             preparedStatement.setTimestamp(2, new Timestamp(entity.getUpdated().getTime()));
>             preparedStatement.setBoolean(3, entity.getVisible());
>             preparedStatement.setString(4, entity.getCarName());
>             preparedStatement.setString(5, entity.getImageUrl());
>             preparedStatement.setString(6, entity.getColor());
>             preparedStatement.setInt(7, entity.getYearsOfIssue());
>             preparedStatement.setDouble(8, entity.getEngineCapacity());
>             preparedStatement.setString(9, entity.getCarNumber());
>             preparedStatement.execute();
>         } catch (SQLException e) {
>             e.printStackTrace();
>         }
> 
> 
>         try (ResultSet resultSet = jpaConfig.getStatement().executeQuery(FIND_CAR_ID_BY_CAR_NUMBER_QUERY
>   entity.getCarNumber())){
>             carId = resultSet.getLong("id");
>         } catch (SQLException e) {
>             System.out.println("problem: = "   e.getMessage());
>         }
> 
> 
>         try (PreparedStatement preparedStatement = jpaConfig.getConnection().prepareStatement(CREATE_DRIVER_CAR_QUERY)) {
>             preparedStatement.setLong(1, driverId);
>             preparedStatement.setLong(2, carId);
>             preparedStatement.execute();
>         } catch (SQLException e) {
>             e.printStackTrace();
>         }
>     }

到達的物體：

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雖然功能幾乎相同，但它使用相同的查詢，但一次是按 car_number 搜索，另一次是按 driver_id：

查詢：private final static String FIND_ALL_SIMPLE_CARS_BY_DRIVER_ID_QUERY = "select id，cars_name，color，years_of_issue，engine_of_capacity，car_number from cars left join driver_car ab on cars.id = ab.car_id where ab.driver_id = ";

    public Map<Long, String> findByDriverId(Long driverId) {
        Map<Long, String> map = new HashMap<>();
        try (ResultSet resultSet = jpaConfig.getStatement().executeQuery(FIND_ALL_SIMPLE_CARS_BY_DRIVER_ID_QUERY
  driverId)) {
            while (resultSet.next()) {
                long id = resultSet.getLong("id");
                String carName = resultSet.getString("cars_name");
                map.put(id, carName);
            }
        } catch (SQLException e) {
            System.out.println("problem: = "   e.getMessage());
        }
        return map;
    }

uj5u.com熱心網友回復：

正如@DaveNewton 已經評論過的那樣，您應該使用 a PreparedStatementforFIND_CAR_ID_BY_CAR_NUMBER_QUERY類似于您已經為插入陳述句執行的方式。這確保了查詢值的正確參考和轉義，從而使您的生活更輕松，您的代碼受 sql 注入攻擊的影響更小。

private final static String FIND_CAR_ID_BY_CAR_NUMBER_QUERY = "select id from cars where car_number = ?";

try (PreparedStatement preparedStatement = jpaConfig.getConnection().prepareStatement(FIND_CAR_ID_BY_CAR_NUMBER_QUERY)) {
  preparedStatement.setString(entity.getCarNumber());
  try (ResultSet resultSet = preparedStatement.executeQuery()) {
    carId = resultSet.getLong("id");
  }
} catch (SQLException e) {
  System.out.println("problem: = "   e.getMessage());
}

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