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;
}
现在,当上述方法完成时,hibernate 会执行某些冗余更新查询,如下所述:
假设我向购物车添加了 2 件商品,所以...
DEBUG PaymentService - Number of items in cart - 2
接下来,在 RENTALS
表中插入一行(预期)
insert
into
rentals
(bookingDate, userID, addressID, rentalID)
values
(?, ?, ?, ?)
USER
和 ADDRESS
表自在 RENTALS
中插入 1 行后更新一次(冗余)
update
users
set
userName=?,
password=?,
firstName=?,
lastName=?,
email=?,
addressID=?
where
userID=?
update
addresses
set
line1=?,
line2=?,
city=?,
state=?,
pincode=?
where
addressID=?
MOVIES
表更新次数与购物车中的商品数量相同(本例中为 2 次,同样是多余的)
update
movies
set
movieName=?,
releaseYear=?,
rating=?,
nCopies=?,
imageUri=?,
plotLine=?
where
movieID=?
/* And another query with different movieID */
在 RENTED_MOVIE
表中插入 2 条记录(预期)
insert
into
rented_movie
(rentalID, returnDate, movieID)
values
(?, ?, ?)
/* And one more with same rentalID and diff. movieID */
最后但并非最不重要的一点是,对 RENTALS
表进行选择查询(为什么??)
上述冗余查询的原因是什么?
我正在使用 Hibernate 4.2.1 和 MySQL 5.5
<小时/>链接到User.hbm.xml
<小时/>更新:似乎无论我尝试什么可能的逆
组合,我似乎都无法避免这些n+2更新(n =购物车):(
有人可以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?
最佳答案
我终于解决了我的问题。问题在于级联设置。我已将其设置为 cascasde="all"
在所有协会中。
我对 Rental.hbm.xml 进行了更改为关联设置特定级联选项:
<!-- 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 <many-to-one name="movie" ../>
中删除了级联因为我通过传递 ID 列表来通过 HQL 更新库存计数,而不是更新对象本身的属性,因为后者会导致 N 个更新语句。
关于java - 当这些表的值没有更改时,为什么 hibernate 会执行冗余更新语句?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16876172/