hi guys i have a problem i have two entities product and category i want to add a category and multiple product in the same form like that in this capture

this is my entity Category

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class Category {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long idcategory;
    
    private String nom;
    
    @JsonManagedReference("category")
    @OneToMany(mappedBy = "category", fetch = FetchType.LAZY,cascade = {CascadeType.PERSIST,CascadeType.MERGE,CascadeType.REMOVE})
    private List<Product> products= new ArrayList<>();
    
     public void add(Product item) {

            if (item != null) {
                if (products == null) {
                    products= new ArrayList<>();
                }

                products.add(item);
                item.setCategory(this);
            }
        }

}

and this is entity Product

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class Product {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long idproduct;
    
    private String nom;
    
    private Integer prix;
    
    @JsonBackReference("category")
    
    @ManyToOne(fetch = FetchType.LAZY)  
    @JoinColumn(name = "categoryproduct", referencedColumnName = "idcategory")
    
    private Category category;

}

and this is my controller

@RequestMapping(method = RequestMethod.POST)
    public void addcategory(@RequestBody Category c) throws IOException {
 
        List<Product> products = c.getProducts();
        products.forEach(item -> c.add(item)
                                
                );  
            
            categorieRepository.save(c);
                
        }

when i try to post a category and multiple product it shows this problem

java.util.ConcurrentModificationException\\r\\n\\tat java.base/java.util.ArrayList.forEach(ArrayList.java:1513)\\r\\n\\tat com.example.users.controller.CategoryController.addcategory(CategoryController.java:46)\\r\\n\\tat java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

i want to know whats wrong with my code and how to fix that guys

CodePudding user response：

You just need to save c, as it already contains everything to save. Ain't need no loop whatsoever. ConcurrentModificationException is when you alter entity while in for-loop. This question here would have helped you:

Hibernate throwing a ConcurrentModificationException

CodePudding user response：

List<Product> products = c.getProducts();
products.forEach(item -> c.add(item));

The problem is here. You are trying to iterate over the list and trying to add items to the same list. It is not possible. You can add a temporary list to add the items.

CodePudding user response：

i fix that i changed List to Set and i changed @Data annotation to @getter and @setter cuz i faced a new error (java.util.AbstractSet.hashCode) and it works now