Java 无法在Hibernate中保存多个关系

这真让我困惑

我有以下课程：

component.java

@Entity
@Table(name = "INGREDIENTS", uniqueConstraints = 
{@UniqueConstraint(columnNames = "NAME")})
public class Ingredient implements Serializable{

@Id
@GeneratedValue
@Column(name = "ingredient_id")
private Long id;

@Column(nullable = false, name = "name")
private String name;

@Column(nullable = false, name = "name")
private Long calories;

public Ingredient() {
}

public Ingredient(String name, Long calories) {
    this.name = name;
    this.calories = calories;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Long getCalories() {
    return calories;
}

public void setCalories(Long calories) {
    this.calories = calories;
}

public Long getId(){
    return this.id;
}

public void setId(Long id) {
    this.id = id;
}

@Entity
@Table(name = "MEALS")
public class Meal implements Serializable {

@ManyToOne
private User user;

@Id
@GeneratedValue
@Column(name = "meal_id")
private Long id;

@ElementCollection(targetClass = Ingredient.class)
private Set<Ingredient> ingredients = new HashSet<>(0);

//More fields and constructors

@ManyToMany(targetEntity = Ingredient.class, cascade = CascadeType.ALL)
@JoinTable(name = "ingredient_meal", joinColumns = {@JoinColumn(name = "meal_id")}, inverseJoinColumns = {@JoinColumn(name = "ingredient_id")})
public List<Ingredient> getIngredients() {
    return ingredients;
}

public void setIngredients(List<Ingredient> ingredients) {
    this.ingredients = ingredients;
}


public Long getId(){
    return this.id;
}

public void setId(Long id) {
    this.id = id;
}

}

fine.java

@Entity
@Table(name = "INGREDIENTS", uniqueConstraints = 
{@UniqueConstraint(columnNames = "NAME")})
public class Ingredient implements Serializable{

@Id
@GeneratedValue
@Column(name = "ingredient_id")
private Long id;

@Column(nullable = false, name = "name")
private String name;

@Column(nullable = false, name = "name")
private Long calories;

public Ingredient() {
}

public Ingredient(String name, Long calories) {
    this.name = name;
    this.calories = calories;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Long getCalories() {
    return calories;
}

public void setCalories(Long calories) {
    this.calories = calories;
}

public Long getId(){
    return this.id;
}

public void setId(Long id) {
    this.id = id;
}

@Entity
@Table(name = "MEALS")
public class Meal implements Serializable {

@ManyToOne
private User user;

@Id
@GeneratedValue
@Column(name = "meal_id")
private Long id;

@ElementCollection(targetClass = Ingredient.class)
private Set<Ingredient> ingredients = new HashSet<>(0);

//More fields and constructors

@ManyToMany(targetEntity = Ingredient.class, cascade = CascadeType.ALL)
@JoinTable(name = "ingredient_meal", joinColumns = {@JoinColumn(name = "meal_id")}, inverseJoinColumns = {@JoinColumn(name = "ingredient_id")})
public List<Ingredient> getIngredients() {
    return ingredients;
}

public void setIngredients(List<Ingredient> ingredients) {
    this.ingredients = ingredients;
}


public Long getId(){
    return this.id;
}

public void setId(Long id) {
    this.id = id;
}

但我一直得到这样一个例外：

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: calories.tracker.app.model.Ingredient
at org.hibernate.engine.internal.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:294)
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:537)
at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:165)
at org.hibernate.persister.collection.AbstractCollectionPersister.writeElement(AbstractCollectionPersister.java:899)
at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1308)
at org.hibernate.action.internal.CollectionRecreateAction.execute(CollectionRecreateAction.java:67)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:463)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:349)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:350)
at 

但是，如果以这种方式保留对象：

    Ingredient i1 = new Ingredient("Potatoes2", 100L);
    session.persist(i1);
    Meal coolMeal = new Meal(user, new Date(115, 0, 8), new Time(19, 0, 0), 
    "8 -  Moules Frites", 1000L);
    coolMeal.getIngredients().add(i1);

---

它很好用，为什么？所有内容都完全相同。

您为

成分

字段声明了两个映射。
一个在字段中，另一个在getter中：

@ElementCollection(targetClass = Ingredient.class)
private Set<Ingredient> ingredients = new HashSet<>(0);    
 ....        
@ManyToMany(targetEntity = Ingredient.class, cascade = CascadeType.ALL)
@JoinTable(name = "ingredient_meal", joinColumns = {@JoinColumn(name = "meal_id")}, inverseJoinColumns = {@JoinColumn(name = "ingredient_id")})
public List<Ingredient> getIngredients() {
    return ingredients;
}

@ElementCollection

设计用于映射非实体类，而

component

是一个实体：

根据Javadoc：

元素集合

定义基本类型或可嵌入类的实例集合

---

您必须使用

@OneToMany（mappedBy=“Ord”，cascade=CascadeType.ALL，fetch=FetchType.LAZY）

，用您的实体名称替换

Ord

。

首先，访问类型要一致，即将所有注释放在字段或属性中，不要混合。然后让我们再看一看。声明的

成分

属于

集合

类型，但getter返回

列表

？抱歉，在尝试使用列表而不是集合时，复制/粘贴会出错，如示例中所示。这不是一个单一的，而是多个单向的