SpringDataJPA @ManyToMany crud

Question

我想插入一件货物。

数据库中已经有或没有某些类别。

我见过许多类似的问题和解决方案，看上去像CascadeType

其实我不明白。

这里有两门课和考试

@Entity
@Table(name = "t_goods")
@Data
public class Goods implements Serializable {
    private static final long serialVersionUID = -7781710173608724249L;
    @Id
    @GenericGenerator(name = "goodsid",strategy = "uuid")
    @GeneratedValue(generator = "goodsid")
    private String goodsId;

    private String goodsName;

    @ManyToMany(cascade = {CascadeType.PERSIST})
    private Set<GoodsCate> goodsCateSet;
}

@Entity
@Table(name = "t_category",uniqueConstraints = { @UniqueConstraint(columnNames = "cateName")})
@Getter
@Setter
public class GoodsCate implements Serializable {
    private static final long serialVersionUID = -8990216455436375344L;
    @Id
    @GenericGenerator(name = "goodscateid",strategy = "uuid")
    @GeneratedValue(generator = "goodscateid")
    private String cateId;

    private String cateName;

   @ManyToMany(mappedBy = "goodsCateSet")
   private Set<Goods> goods;
}

@Test
void test(){

    Goods goods = new Goods();
    goods.setGoodsName("apple");

    GoodsCate food = new GoodsCate();
    food.setCateName("food");
    GoodsCate fooddb= goodsCateRepo.findGoodsCateByCateName(food.getCateName());
    if(fooddb!=null){
        food=fooddb;
    }
    GoodsCate vegetable= new GoodsCate();
    vegetable.setCateName("vegetable");
    GoodsCate vegetabledb = goodsCateRepo.findGoodsCateByCateName(vegetable.getCateName());
    if(vegetabledb!=null){
        vegetable = vegetabledb;
    }
    Set<GoodsCate> goodsCates = Sets.newSet(food, vegetable);


     goods.set(goodsCates);
     // goodsRepo is a interface extends jpaReposity
     goodsRepo.save(goods);

}

它抛出

传递给org.springframework.dao.InvalidDataAccessApiUsageException:的persist:com.xx.xxx.GoodsCate分离实体

Answer 1

看起来你还没有把你的分类和商品联系起来。

我建议添加两个实用方法(例如，商品中的addCategory(Category category)和类别中的addGood(Goods good) )，它们用于同步双向关联的双方。当您使用双向关联时，应该始终提供这些方法，否则，您将面临非常微妙的状态传播问题。

在Goods中

public void addCategory(Category category) {
        categories.add(category);
        category.getGoods().add(this);
    }

在Category中

public void addGood(Good good) {
        goods.add(good);
        good.getCategory().add(this);
    }

Note：还不要忘记添加remove实用程序，就像上面的一样。

然后您可以使用下面的代码

@Test
    void test(){

        Goods goods = new Goods();
        goods.setGoodsName("apple");

        GoodsCate food = new GoodsCate();
        food.setCateName("food");
        GoodsCate fooddb= goodsCateRepo.findGoodsCateByCateName(food.getCateName());
        if(fooddb!=null){
            food=fooddb;
        }
        GoodsCate vegetable= new GoodsCate();
        vegetable.setCateName("vegetable");
        GoodsCate vegetabledb = goodsCateRepo.findGoodsCateByCateName(vegetable.getCateName());
        if(vegetabledb!=null){
            vegetable = vegetabledb;
        } 
        //********After adding mentioned utilites********    
         goods.addCategory(food);
         goods.addCategory(vegetable);
         // goodsRepo is a interface extends jpaReposity
         goodsRepo.save(goods);

    }

多到多个最佳实践的文章之一