Spring JPA hibernate如何从@OneToMany父列中持久化子项（删除、添加或更新）？

Question

我试图解决这个问题已经有一段时间了，但我还没有实现100%的解决方案。首先，我必须描述我的问题。我正在开发一个餐厅应用程序，在所有实体中，我有实体成分，正如你们所知，成分可以由特定数量的其他成分组成。所以我创建了一个实体子成分，带有一个嵌入的Id。

为了保留子成分列表，我尝试了级联和去除孤儿的组合，每种组合对某些操作有效，但对其他操作无效。

我从使用CascadeType开始。所有和新的子成分成功地从@OneToMany属性中保留，但如果我试图从子成分列表中删除子成分并保存，则会出现此错误。

JAVAlang.StackOverflower错误：在com上为空。mysql。希杰。民族复兴。execSQL（NativeSession.java:1109）~[mysql-connector-java-8.0.23.jar:8.0.23]。。。。。。

我在网上登录了一个解决方案，我发现我必须使用孤儿移除=true我试过了，但是它不起作用，直到我把级联从CascadeType. ALL改为CascadeType. PERSIST。但是这一个使得新的子成分的持久性这个错误提前

原因：javax。坚持不懈EntityNotFoundException:找不到com。实例雷斯托。领域id为com的子成分。实例雷斯托。领域SubIngredientKey@51b11186........

以下是我的优点：

@Entity
public class Ingredient {

@Id
@GeneratedValue( strategy = GenerationType.IDENTITY)
@Column(name="ID")
private long id;


@NotNull
@Column(unique=true)
private String name;
private String photoContentType;
@Lob
private byte[] photo;

@JsonIgnoreProperties({"photoContentType","photo"})
@ManyToOne
private IngredientType ingredientType;


@OneToMany(mappedBy = "embId.ingredientId", fetch = FetchType.EAGER,   
cascade = CascadeType.ALL /*or orphanRemoval = true, cascade = CascadeType.PERSIST*/ )
private Set<SubIngredient> subIngredients =  new HashSet<SubIngredient>();

getters and setters.....

和

@Entity
@AssociationOverrides({
@AssociationOverride(name = "embId.ingredientId", 
    joinColumns = @JoinColumn(name = "ING_ID")),
@AssociationOverride(name = "embId.subIngredientId", 
    joinColumns = @JoinColumn(name = "SUB_ING_ID")) })
public class SubIngredient {


@EmbeddedId
private SubIngredientKey embId = new SubIngredientKey();

private double quantity;

getters and setters....

和

@Embeddable
public class SubIngredientKey implements Serializable{

@ManyToOne(cascade = CascadeType.ALL)
private Ingredient ingredientId;


@ManyToOne(cascade = CascadeType.ALL)
private Ingredient subIngredientId;

getters and setters...

Answer 1

感谢Pilpo，我对may实体进行了一些更改，并重写了equals/hashcode方法，从而解决了这个问题。

@Embeddable
public class SubIngredientKey implements Serializable{


private Long ingredientId;


private Long subIngredientId;
/**
 * @return the ingredientId
 */


@Override
public int hashCode() {
    return Objects.hash(ingredientId, subIngredientId);
}
@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (!(obj instanceof SubIngredientKey)) {
        return false;
    }
    SubIngredientKey other = (SubIngredientKey) obj;
    return Objects.equals(ingredientId, other.ingredientId)
            && Objects.equals(subIngredientId, other.subIngredientId);
}

}



@Entity
public class SubIngredient {


@EmbeddedId
private SubIngredientKey embId = new SubIngredientKey();

@ManyToOne(fetch = FetchType.LAZY)
@MapsId("ingredientId")
private Ingredient ingredient;

@ManyToOne(fetch = FetchType.LAZY)
@MapsId("subIngredientId")
private Ingredient subIngredient;

private double quantity;

@JsonIgnore
public SubIngredientKey getId() {
    return embId;
}
public void setId(SubIngredientKey id) {
    this.embId = id;
}


@JsonIgnoreProperties({"subIngredients","photo","photoContentType","ingredientType"})
public Ingredient getIngredient() {
    return ingredient;
}
public void setIngredient(Ingredient ingredient) {
    this.ingredient = ingredient;
}



@JsonIgnoreProperties({"subIngredients","photo","photoContentType","ingredientType"})
public Ingredient getSubIngredient() {
    return subIngredient;
}
public void setSubIngredient(Ingredient subIngredient) {
    this.subIngredient = subIngredient;
}

public double getQuantity() {
    return quantity;
}

public void setQuantity(double quantity) {
    this.quantity = quantity;
}

@Override
public String toString() {
    return "subIngredient= " + getSubIngredient().getName() + " , quantity=  " + getQuantity();
}


@Override
public int hashCode() {
    return Objects.hash(ingredient,subIngredient);
}
@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (!(obj instanceof SubIngredient)) {
        return false;
    }
    SubIngredient other = (SubIngredient) obj;
    return Objects.equals(ingredient, other.ingredient) && Objects.equals(subIngredient, other.subIngredient);
}

}



@Entity
public class Ingredient {

@Id
@GeneratedValue( strategy = GenerationType.IDENTITY)
@Column(name="ID")
private long id;


@NotNull
@Column(unique=true)
private String name;
private String photoContentType;
@Lob
private byte[] photo;

@JsonIgnoreProperties({"photoContentType","photo"})
@ManyToOne
private IngredientType ingredientType;


@OneToMany(mappedBy = "embId.ingredientId", fetch = FetchType.EAGER, cascade = 
CascadeType.ALL, orphanRemoval = true)
private Set<SubIngredient> subIngredients =  new HashSet<SubIngredient>();



public long getId() {
    return id;
}

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

public String getName() {
    return this.name;
}

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

public String getPhotoContentType() {
    return photoContentType;
}



public void setPhotoContentType(String photoContentType) {
    this.photoContentType = photoContentType;
}

public byte[] getPhoto() {
    return photo;
}

public void setPhoto(byte[] photo) {
    this.photo = photo;
}


public IngredientType getIngredientType() {
    return this.ingredientType;
}
public void setIngredientType(IngredientType ingredientType) {
    this.ingredientType = ingredientType;
}



public Set<SubIngredient> getSubIngredients() {
    return subIngredients;
}

public void setSubIngredients(Set<SubIngredient> subIngredients) {
    this.subIngredients = subIngredients;
}

public void addSubIngredient(SubIngredient subIngredient) {
    this.subIngredients.add(subIngredient);
}

@Override
public String toString() {
     String subIngsText = "";
     for(var subIngredient:this.subIngredients) {
         subIngsText = subIngsText + ", " +  subIngredient.toString();
     }
    return "{id= "+id+",name=" + name +", ingredients="+subIngsText+"}";
}

@Override
public int hashCode() {
    
    return Objects.hash(name);
}

@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (!(obj instanceof Ingredient)) {
        return false;
    }
    Ingredient other = (Ingredient) obj;
    return Objects.equals(name, other.name);
}
}

Answer 2

stackoverflow之所以发生，是因为您使用了集合

hashcode Ingredient -> hashcode SubIngredient -> hashcode Ingredient 

这将导致无限次调用hashcode方法。这就是为什么会出现堆栈溢出错误。

同样的事情也会发生在equals/toString上。

因此，为了避免这样的问题，最好重写hashcode，等于和toString。