我在使用EntityManager.merge()时遇到了一些非常奇怪的行为。这是发生了什么。我有一个REST API设置，包括Spring MVC，Hibernate和JPA，用于插入，更新和删除MySQL数据库中的项目。插入和更新函数都使用EntityManager.merge()，它们都可以在99％的时间内正常工作。
但是，有一次，似乎是第一次调用更新记录，它会在数据库中创建记录的副本，然后返回原始记录并对其进行更改。
我真的不知道为什么会这样。你会认为如果它创建了一个重复的记录，它会编辑那个，但是nope，在更新时会创建副本，放弃它，然后返回到第一个记录进行更改。
我正在思考它，因为我的实体bean中的哈希码和等于设置的方式可能就是这样。虽然我没有看到任何问题，因为我已经根据唯一的密钥而不是ID。
我的代码如下。关于正在发生的事情的任何想法将是一个很大的帮助。
这是实体：
@Entity
@Table(name = "DAY_ITEM")
public class DayItem implements GtEntity, Serializable{
private Long id;
private String email;
private String name;
private BigDecimal amount;
private Integer modId;
private Integer fmOrder;
private String modName;
private Date daysDate;
private String daysDateString;
private Long foodId;
private Long mealId;
private FoodItem foodItem;
private MealItem mealItem;
private ArrayList<FoodItem> foodItems;
private ArrayList<MealItem> mealItems;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Basic
@Column(name = "EMAIL", nullable = false, length = 50)
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Basic
@Column(name = "NAME", nullable = true, length = 100)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Basic
@Column(name = "AMOUNT", nullable = true)
public BigDecimal getAmount() {
return amount;
}
public void setAmount(BigDecimal amount) {
this.amount = amount;
}
@Basic
@Column(name = "MOD_ID", nullable = false)
public Integer getModId() {
return modId;
}
public void setModId(Integer modId) {
this.modId = modId;
}
@Basic
@Column(name = "FM_ORDER", nullable = false)
public Integer getFmOrder() {
return fmOrder;
}
public void setFmOrder(Integer fmOrder) {
this.fmOrder = fmOrder;
}
@Basic
@Column(name = "MOD_NAME", nullable = true, length = 50)
public String getModName() {
return modName;
}
public void setModName(String modName) {
this.modName = modName;
}
@Basic
@Column(name = "DAYS_DATE", nullable = false)
public Date getDaysDate() {
return daysDate;
}
public void setDaysDate(Date daysDate) {
this.daysDate = daysDate;
}
@Transient
public String getDaysDateString() {
if(daysDateString == null) {
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
return formatter.format(daysDate);
}
return daysDateString;
}
public void setDaysDateString(String daysDateString) {
this.daysDateString = daysDateString;
}
@Basic
@Column(name = "FOOD_ID", nullable = true)
public Long getFoodId() {
return foodId;
}
public void setFoodId(Long foodId) {
this.foodId = foodId;
}
@Basic
@Column(name = "MEAL_ID", nullable = true)
public Long getMealId() {
return mealId;
}
public void setMealId(Long mealId) {
this.mealId = mealId;
}
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "FOOD_ID", referencedColumnName = "ID",
updatable = false, insertable = false)
public FoodItem getFoodItem() {
return foodItem;
}
public void setFoodItem(FoodItem foodItem) {
this.foodItem = foodItem;
}
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "MEAL_ID", referencedColumnName = "ID",
updatable = false, insertable = false)
public MealItem getMealItem() {
return mealItem;
}
public void setMealItem(MealItem mealItem) {
this.mealItem = mealItem;
}
@Transient
public ArrayList<FoodItem> getFoodItems() {
return foodItems;
}
public void setFoodItems(ArrayList<FoodItem> foodItems) {
this.foodItems = foodItems;
}
@Transient
public ArrayList<MealItem> getMealItems() {
return mealItems;
}
public void setMealItems(ArrayList<MealItem> mealItems) {
this.mealItems = mealItems;
}
public void makeDaysDate() throws ParseException{
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
this.daysDate = new Date(formatter.parse(this.daysDateString).getTime());
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof DayItem)) return false;
DayItem dayItem = (DayItem) o;
if (!getEmail().equals(dayItem.getEmail())) return false;
if (!getModId().equals(dayItem.getModId())) return false;
if (!getFmOrder().equals(dayItem.getFmOrder())) return false;
if (!getDaysDateString().equals(dayItem.getDaysDateString())) return false;
if (getFoodId() != null ? !getFoodId().equals(dayItem.getFoodId()) : dayItem.getFoodId() != null) return false;
return getMealId() != null ? getMealId().equals(dayItem.getMealId()) : dayItem.getMealId() == null;
}
@Override
public int hashCode() {
int result = getEmail().hashCode();
result = 31 * result + getModId().hashCode();
result = 31 * result + getFmOrder().hashCode();
result = 31 * result + getDaysDateString().hashCode();
result = 31 * result + (getFoodId() != null ? getFoodId().hashCode() : 0);
result = 31 * result + (getMealId() != null ? getMealId().hashCode() : 0);
return result;
}
}
这是执行初始创建的代码：
@Override
public List<DayItem> saveDayItem(DayItem item) throws Exception {
EntityManager manager = entityManagerFactory.createEntityManager();
EntityTransaction tx = manager.getTransaction();
List<DayItem> results = null;
try {
tx.begin();
manager.merge(item);
manager.flush();
manager.clear();
results = findUserDay(item.getDaysDate(), item.getEmail(), manager);
tx.commit();
} catch (Exception e) {
tx.rollback();
throw e;
} finally {
manager.close();
return results;
}
}
以下是执行更新的代码：
public <T extends GtEntity> T store(T entity) throws Exception {
T managedEntity = null;
EntityManager manager = entityManagerFactory.createEntityManager();
EntityTransaction tx = manager.getTransaction();
try{
tx.begin();
managedEntity = manager.merge(entity);
tx.commit();
}catch(RuntimeException e){
tx.rollback();
throw e;
}finally {
manager.close();
return managedEntity;
}
}
答案 0 :(得分：0)
由于您实现了equals和hasCode，Hibernate将使用这些方法来查找要更新的实体。假设已分离的对象已更改，equals和hasCode将永远不会返回与附加实体相同的值，因此Hibernate将假定它是一个新实例。
您应该阅读有关equals and hasCode。