根据用户输入在 PreparedStatement 中使用 setTime() 或 setNull()

Question

我正在我的 JAVA 应用程序和 PostgreSQL 数据库中进行过滤搜索。

我有以下 PostgreSQL 查询以选择有关航班的数据：

String query =  "SELECT flight.flight_id, route.from_location, route.to_location, flight.base_cost, flight.departure_date, flight.departure_time, flight.arrival_date, flight.arrival_time, aircraft.manufacturer, aircraft.seats " +
                "FROM flight " +
                "INNER JOIN route ON flight.route_id = route.route_id " +
                "INNER JOIN aircraft ON flight.aircraft_id = aircraft.aircraft_id " +
                "WHERE " +
                "(from_location = CASE WHEN ? IS NULL THEN from_location ELSE ? END) AND " +
                "(to_location = CASE WHEN ? IS NULL THEN to_location ELSE ? END) AND " +
                "(base_cost = CASE WHEN ? IS NULL THEN base_cost ELSE ? END) AND " +
                "(departure_date = CASE WHEN ? IS NULL THEN departure_date ELSE ? END) AND " +
                "(departure_time = CASE WHEN ? IS NULL THEN departure_time ELSE ? END) AND " +
                "(arrival_date = CASE WHEN ? IS NULL THEN arrival_date ELSE ? END) AND " +
                "(arrival_time = CASE WHEN ? IS NULL THEN arrival_time ELSE ? END)";

然后我有这样的 Java 代码：

    ResultSet rs = null;
    PreparedStatement prepStatement = connection.prepareStatement(query);
    try {
                if (!showFromTxtField.getText().trim().isEmpty()) {
                    prepStatement.setString(1, showFromTxtField.getText());
                    prepStatement.setString(2, showFromTxtField.getText());
                } else {
                    prepStatement.setNull(1, java.sql.Types.VARCHAR );
                    prepStatement.setNull(2, java.sql.Types.VARCHAR );
                }
                if (!showToTxtField.getText().trim().isEmpty()) {
                    prepStatement.setString(3, showToTxtField.getText());
                    prepStatement.setString(4, showToTxtField.getText());
                } else {
                    prepStatement.setNull(3, java.sql.Types.VARCHAR );
                    prepStatement.setNull(4, java.sql.Types.VARCHAR );
                }
                if (!showCostTxtField.getText().trim().isEmpty()) {
                    prepStatement.setFloat(5, Float.parseFloat(showCostTxtField.getText()));
                    prepStatement.setFloat(6, Float.parseFloat(showCostTxtField.getText()));
                } else {
                    prepStatement.setNull(5, java.sql.Types.FLOAT );
                    prepStatement.setNull(6, java.sql.Types.FLOAT);
                }
                LocalDate depDate = showDepDateDatePicker.getValue();
                if (depDate != null) {
                    prepStatement.setDate(7, Date.valueOf(depDate));
                    prepStatement.setDate(8, Date.valueOf(depDate));
                } else {
                    prepStatement.setNull(7, java.sql.Types.DATE );
                    prepStatement.setNull(8, java.sql.Types.DATE);
                }
                if (!showDepTimeTxtField.getText().trim().isEmpty()) {
                    DateFormat formatter = new SimpleDateFormat("HH:mm:ss");
                    try {
                        Time timeValue = new Time(formatter.parse(showDepTimeTxtField.getText()).getTime());
                        prepStatement.setTime(9, timeValue);
                        prepStatement.setTime(10, timeValue);
                    } catch (ParseException e) {
                        e.printStackTrace();
                    }
                } else {
                    prepStatement.setNull(9, java.sql.Types.TIME );
                    prepStatement.setNull(10, java.sql.Types.TIME );
                }
                LocalDate arrDate = showArrDatePicker.getValue();
                if (arrDate != null) {
                    prepStatement.setDate(11, Date.valueOf(arrDate));
                    prepStatement.setDate(12, Date.valueOf(arrDate));
                } else {
                    prepStatement.setNull(11, java.sql.Types.DATE );
                    prepStatement.setNull(12, java.sql.Types.DATE);
                }
                if (!showArrTimeTxtField.getText().trim().isEmpty()) {
                    DateFormat formatter = new SimpleDateFormat("HH:mm:ss");
                    try {
                        Time timeValue = new Time(formatter.parse(showArrTimeTxtField.getText()).getTime());
                        prepStatement.setTime(13, timeValue);
                        prepStatement.setTime(14, timeValue);
                    } catch (ParseException e) {
                        e.printStackTrace();
                    }
                } else {
                    prepStatement.setNull(13, java.sql.Types.TIME );
                    prepStatement.setNull(14, java.sql.Types.TIME );
                }

                rs = prepStatement.executeQuery();
      } catch (SQLException e) {
                e.printStackTrace();
            }

所以重点是 return 只有那些符合文本字段标准的航班。如果任何文本字段留空，则查询应 return 该特定条件的所有航班，但使用其他非空条件进行过滤。

我在参数 $9 处出错。当我将输入 showDepTimeTxtField 的 String（例如“18:00:00”）转换为 java.sql.Time 对象时，我可以将其用作 prepStatement 方法的输入参数 setTime() 我的查询应该 return 只有航班（满足其他条件） departure_time 与输入文本字段的时间相同。如果文本字段留空且没有 String 输入，我的查询应该 return 航班与他们拥有的任何 departure_time，来自我的数据库。

我的问题是，当我运行我的代码出现以下错误时： org.postgresql.util.PSQLException: 错误：无法确定参数 $9 的数据类型，我在用字符串填充 departureTimeTxtField 或将其留空时得到，因此参数 departure_time 应该设置为 NULL，我的查询应该 return 航班与所有 departure_time。

所以我假设 setTime() 方法参数 timeValue 和从 String 到 java.sql.Time 的转换有问题。

如何进行正确的转换以便消除该错误？

编辑：SQL 查询和 Java 源代码已更新。

Answer 1

错误是由于 SQL 中的无效 CASE 语法（而不是因为时间格式）引起的，请查看 CASE 语法 here。

此外，从这个例子来看，您似乎正在尝试获取起飞时间为空或文本字段中存在时间的所有航班，在这种情况下，我建议采用以下方法：

ResultSet rs = null;
PreparedStatement prepStatement = null;
if (!departureTimeTxtField.getText().trim().isEmpty()) {
    DateFormat formatter = new SimpleDateFormat("HH:mm:ss");
    Time timeValue = new Time(formatter.parse(departureTimeTxtField.getText()).getTime());
    prepStatement  = connection.prepareStatement("SELECT * FROM flights WHERE departure_time = ?");
    prepStatement.setTime(1, timeValue);
}else{
    prepStatement  = connection.prepareStatement("SELECT * FROM flights WHERE departure_time IS NULL");
}
rs = prepStatement.executeQuery();

Answer 2

我使用 COALESCE() 而不是 CASE WHEN ... 解决了这个问题：

String query = "SELECT * FROM flights WHERE departure_time = COALESCE(?, departure_time)";

根据用户输入在 PreparedStatement 中使用 setTime() 或 setNull()

Using setTime() or setNull() in PreparedStatement depending on user input

java

sql

postgresql

jdbc

prepared-statement