Java 为什么hibernate在没有更改这些表的值的情况下执行冗余的update语句？

我有以下代码：

public int makePayment(User forUser, Collection<Movie> cartItems, 
     Address deliverTo) 
{
   int returnCode = 0;

   LOGGER.debug("Number of items in cart - {}", cartItems.size());

   Rental rental = new Rental();
   rental.setRentalID(RandomStringUtils.randomAlphanumeric(ID_LENGTH).toUpperCase());
   rental.setUser(forUser); // Update reference to parent
   rental.setAddress(deliverTo);

   // Each rental has its own set of rented movies
   Set<RentedMovie> rentedMovies = new HashSet<>(cartItems.size());
   for (Iterator<Movie> iterator = cartItems.iterator(); iterator.hasNext();)
   {
      Movie movie = iterator.next();
      RentedMovie rentedMovie = new RentedMovie();
      rentedMovie.setMovie(movie);
      rentedMovie.setRental(rental); // Update reference to parent
      rentedMovies.add(rentedMovie);
   }

   rental.setRentedMovies(rentedMovies);
   rentalDAO.create(rental);

   Set<Rental> userRentals = userDAO.findById(forUser.getUserID()).getRentals();
   userRentals.add(rental); // Add to existing set of rentals

   try
   {
      String addressID = addressDAO.create(deliverTo);
      LOGGER.debug("Delivery Address successfully inserted. Generated address ID - {}", addressID);

      forUser.setRentals(userRentals);
      userDAO.update(forUser); // Internally calls session.merge()
   }
   catch (Exception e) {
      returnCode = -1;
      LOGGER.error("Exception during payment - {}", e.getMessage(), e);
   }

   return returnCode;
}

接下来，在

RENTALS

表中插入一行（预期）

用户

和

地址

表在

租赁中插入1行后更新一次（冗余）

MOVIES
表的更新次数与购物车中的项目数相同（在这种情况下为2，同样是多余的）

在
u电影
表中插入2条记录（预计）

最后，但并非最不重要的一点是，对
RENTALS
表的select查询（为什么？？）

上述冗余查询的原因是什么

我正在使用Hibernate4.2.1和MySQL5.5


链接到

链接到

链接到


更新：似乎无论我尝试的是
反向
的任何可能组合，我似乎都无法避免这些n+2次更新（n=购物车中的电影数量）：(

有人能告诉我这是否是已知行为吗？如果是，可能的解决方法是什么？
我终于设法解决了我的问题。问题在于层叠设置。我在所有关联中将其设置为
cascascascade=“all”

我对设置关联的特定级联选项进行了更改：

<!-- n:1 mapping with User -->
<many-to-one name="user"
   column="userID"
   class="User"
   not-null="true"
   fetch="join"
   cascade="none" /> <!-- No cascading required for User -->

<!-- 1:1 mapping with Address. Association is MANDATORY. -->
<many-to-one name="address"
      column="addressID"
      class="Address"
      unique="true"
      not-null="true"
      cascade="persist"/> <!-- Either create a new delivery address or use an existing user address -->

<!-- m:n mapping with Movie -->
<set name="rentedMovies" table="rented_movie" lazy="true" 
    cascade="save-update, delete-orphan"> <!-- Selective update / delete -->
   <key column="rentalID"/>
   <composite-element class="RentedMovie">
      <parent name="rental"/>
      <property name="returnDate" column="returnDate" type="date" not-null="true"/>
      <many-to-one name="movie" column="movieID" class="Movie" not-null="true" fetch="join"/>
   </composite-element>
</set>



我从
中删除了级联，因为我正在通过HQL更新库存计数，方法是传递ID列表，而不是更新对象本身中的属性，因为后者会导致N个update语句

insert 
into
  rentals
  (bookingDate, userID, addressID, rentalID) 
values
  (?, ?, ?, ?)

update
  users 
set
  userName=?,
  password=?,
  firstName=?,
  lastName=?,
  email=?,
  addressID=? 
where
  userID=?

update
  addresses 
set
  line1=?,
  line2=?,
  city=?,
  state=?,
  pincode=? 
where
  addressID=?

update
  movies 
set
  movieName=?,
  releaseYear=?,
  rating=?,
  nCopies=?,
  imageUri=?,
  plotLine=? 
where
  movieID=?

/* And another query with different movieID */

insert 
into
  rented_movie
  (rentalID, returnDate, movieID) 
values
  (?, ?, ?)

/* And one more with same rentalID and diff. movieID */

<!-- n:1 mapping with User -->
<many-to-one name="user"
   column="userID"
   class="User"
   not-null="true"
   fetch="join"
   cascade="none" /> <!-- No cascading required for User -->

<!-- 1:1 mapping with Address. Association is MANDATORY. -->
<many-to-one name="address"
      column="addressID"
      class="Address"
      unique="true"
      not-null="true"
      cascade="persist"/> <!-- Either create a new delivery address or use an existing user address -->

<!-- m:n mapping with Movie -->
<set name="rentedMovies" table="rented_movie" lazy="true" 
    cascade="save-update, delete-orphan"> <!-- Selective update / delete -->
   <key column="rentalID"/>
   <composite-element class="RentedMovie">
      <parent name="rental"/>
      <property name="returnDate" column="returnDate" type="date" not-null="true"/>
      <many-to-one name="movie" column="movieID" class="Movie" not-null="true" fetch="join"/>
   </composite-element>
</set>