flush() doesn't work by default in @Transaction

[chikacow]

Hi, I noticed a problem that when I am not manually using entityManager.flush() below, the result i got for tableNo in return statement and what I have in the database(which got the data updated) is different. For example, my input for tableNo is "a b c" and my expected result both for in database and the return is "abc". However I only have "abc" in the database and still "a b c" in the return statement. When I uncomment the entityManager.flush() things work perfectly, but do I have to do so since the flush() should be automatically done?

Seat.java

  @PreUpdate
    private void preUpdate() {
        this.tableNo = this.tableNo.trim().replaceAll("\\s+", "");;
    } 

SeatService.java

  @Transactional
      public Seat.SeatResponseDTO updateSeat(Long id, Seat.SeatRequestDTO requestDTO) {
          Seat seat = getSeatById(id); //which called
  
          if (!seat.getTableNo().equals(requestDTO.getTableNo())) {
              if (seatRepository.existsByTableNo(requestDTO.getTableNo())) {
                  throw new IllegalArgumentException("Table number already exists");
              }
              seat.setTableNo(requestDTO.getTableNo());
          }
  
          seat.setDescription(requestDTO.getDescription());
          seat.setStatus(TableStatus.fromString(requestDTO.getStatus()));
  
          /**
           * bug, this should be automatically called but i have to do it manually to achieve something obvious
           */
          entityManager.flush();
          
          return Seat.SeatResponseDTO.builder()
                  .tableNo(seat.getTableNo())
                  .description(seat.getDescription())
                  .status(seat.getStatus())
                  .build();
      }

[schauder]

This is not a bug but normal JPA behavior. And completely unrelated to Spring Data JPA.

The life cycle event happens when data gets flushed to the database.
This happens at the end of the transaction or when you explicitly call flush.

In the first case you construct your DTO before the event handling happens, since you see the unmodified data.

[chikacow]

Thanks for your response!

I have resolved this. The problem is caused by the difference between @PrePersist and @PreUpdate.

When I call entityManager.persist(), the @PrePersist seems to work immediately while the @PreUpdate will only work until the flush() is activated.

That's why the result in my response DTO is different between my 2 methods updateSeat() and createSeat() (Which drove me crazy because the 2 functions basically does the same thing)