How to convert Datetime to Date in JPA query

Question

I'm writing complicated queries using Spring data JPA, let's say a statistics query.

@Data
@AllArgsConstructor
@NoArgsConstructor
public class StatisticsPair {
  private LocalDateTime time;
  private BigDecimal balance;
}

@Data
@Entity
@Table(name="t_order")
public class Order {
  private LocalDateTime createdTime;
  private BigDecimal amount;
  private OrderStatus status;
}

query in a repository:

@Query("select new xxx.StatisticsPair(createdTime, sum(amount)) from Order where createdTime >= ?1 and createdTime <= ?2 and status = xxx.OrderStatus.COMPLETED group by createdTime")
List<StatisticsPair> statAmountByDay(LocalDateTime from, LocalDateTime to);

method statAmountByDay gives me a result like:

[
  {"time": "2006-01-02 15:04:05", "balance": 100.00}
  {"time": "2006-01-02 16:04:05", "balance": 200.00}
  {"time": "2006-01-03 15:04:05", "balance": 200.00}
]

but I want statistics by day, only need date, time is useless, expected result:

[
  {"time": "2006-01-02", "balance": 300.00}
  {"time": "2006-01-03", "balance": 200.00}
]

so I want to know how to convert createdTime (datetime type) to Date type, like function DATE(createdTime) in mysql, but I don't wanna use native query, because my code runs on different ENV, use different databases.

Answer 1

I know it's not the best way to do it, but until I find a better solution, you can manipulate the returned time as a String (using SUBSTRING )

xxx.StatisticsPair(substring(cast(createdTime as nvarchar(19)), 1, 10), sum(amount))

or try:

xxx.StatisticsPair(cast(createdTime as date), sum(amount))

Answer 2

You have two possible solutions:

1. Change LocalDateTime in object StatisticsPair to have LocalDate instead of LocalDateTime and hopefully spring JPA will take only the date component:

....

@Data
@AllArgsConstructor
@NoArgsConstructor
public class StatisticsPair {
    private LocalDate date;
    private BigDecimal balance;
}

2. Second solution is to manipulate with java and java streams over the list of StatisticsPair:

....

List<StatisticsPair> list = ... ;
List<StatisticsPairWithDate> listWithDate;
listWithDate = list
            .stream()
            .map(sp-> 
                    new StatisticsPairWithDate(
                            sp.getTime().toLocalDate(), 
                            sp.getBalance()))
            .collect(Collectors.toList()); 

....

@Data
@AllArgsConstructor
@NoArgsConstructor
public class StatisticsPairWithDate {
  private LocalDate date;
  private BigDecimal balance;
}

=============================================

@Query("select new xxx.StatisticsPair(createdTime, sum(amount)) from Order where createdTime >= ?1 and createdTime <= ?2 and status = xxx.OrderStatus.COMPLETED group by createdTime")
List<StatisticsPair> statAmountByDay(LocalDate from, LocalDate to);