Question

我一直试图用Play Framework 2.5学习Ebean几天。我可以做我想做的一切，除了删除一个实体（我不想使用sql，除非有必要）。每次我尝试删除商品（myoffer.delete()）时，都会抛出此异常：

[RuntimeException: get author on [model.Offer] type[null] threw error.]

优惠类是：

@Entity
public class Offer extends Model {

    //Basic Fields
    @Id
    public Long id;

    @Constraints.Required
    @Column(nullable = false)
    public String title;

    @Constraints.Required
    @Column(nullable = false)
    public String description;


    @Column(nullable = false)
    public Date publishDate;

    public Date startDate;

    public Date finishDate;

    @Column(nullable = false)
    public boolean sold;

    //Relations
    @JoinColumn(nullable = false)
    @ManyToOne(cascade = CascadeType.ALL)
    public User author;

    @JoinColumn(nullable = false)
    @ManyToOne(cascade = CascadeType.ALL)
    public OfferCategory category;

    @ManyToMany(cascade = CascadeType.ALL, mappedBy="offers")
    public List<Image> images;

    //Finder
    public static Finder<Long, Offer> find = new Finder<>(Offer.class);

    @PreRemove
    protected void preRemove() {
        for(Image img:this.images){
            img.offers.remove(this);
        }
        this.author.offers.remove(this);
    }
    //Constructors
    public Offer(){}
}

我在这里做错了什么？

编辑1：

在这种情况下，由于删除方法的使用非常少，我使用的是纯SQL查询。我知道方法性能可能不是最好的，但至少它起作用了：

@Override
public void delete(Long... idsLongArray) {
    StringBuilder deleteImages = new StringBuilder("DELETE FROM image_offer WHERE offer_id IN (?)");
    StringBuilder deleteOffer = new StringBuilder("DELETE FROM offer WHERE id IN (?)");
    int j;
    int k;
    for (int i = 1; i < idsLongArray.length; i++) {
        j = deleteImages.lastIndexOf("?");
        k = deleteOffer.lastIndexOf("?");
        deleteImages.replace(j, j + 1, "?,?");
        deleteOffer.replace(k, k + 1, "?,?");
    }
    SqlUpdate imgQuery = Ebean.createSqlUpdate(deleteImages.toString());
    SqlUpdate offerQuery = Ebean.createSqlUpdate(deleteOffer.toString());
    for (int i = 0; i < idsLongArray.length; i++) {
        imgQuery.setParameter(i + 1, idsLongArray[i]);
        offerQuery.setParameter(i + 1, idsLongArray[i]);
    }
    imgQuery.execute();
    offerQuery.execute();

    /*List<Offer> offers = Offer.find.select("id").where().in("id", idsLongArray).findList();
    for(Offer offer: offers){
        offer.save();
        offer.delete();
    }*/
}

EDIT2：

使用@Salem在评论中告诉我的建议，我们使其成功。我只需要从多对一关系中移除cascade=CascadeType.ALL参数。

@JoinColumn(nullable = false)
@ManyToOne
public User author;

@JoinColumn(nullable = false)
@ManyToOne
public OfferCategory category;

我的最终删除方法如下所示：

public void delete(Long... idsLongArray) {
    for(Long id: idsLongArray){
        Offer.find.byId(id).delete();
    }
}

在Play-Framework中删除Ebean模型

编辑1：

EDIT2：

0 个答案: