ManyToOne saves null reference - spring-boot

Question

I am learning Springboot/Hibernate and am having some trouble with ManyToOne notation.
I have three models: Order, OrderDetail, and Product. Each Order has several OrderDetails (OneToMany, this works fine) and each OrderDetail holds an id of one Product (products can be repeated, therefore it should be ManyToOne).
What happens is that everytime I try to save an order the details get created and saved but the products (which already exist in my database) within each detail are being set null. I have tried everything I found on the internet for the past 4 hours but haven't found what's causing my issue yet.
Minimal code, let me know if you need more details:
#RestController
public class OrderController {
#Autowired
OrderRepository orderRepository;
#PostMapping("/orders")
public Order addOrder(#RequestBody Order order)
{
return orderRepository.save(order);
}
}
#Entity
#Table(name="orders")
public class Order {
#Id
#GeneratedValue
#Column(name = "order_id")
private Long id;
//...
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
#JoinColumn(name = "order_id")
#Getter
#Setter
private List<OrderDetail> orderDetailList;
//...
^This works just fine
#Entity
#Table(name="order_details")
public class OrderDetail {
#Id
#GeneratedValue
#Column(name = "order_detail_id")
private Long id;
//...
#ManyToOne(/*optional = false, */cascade = CascadeType.ALL, targetEntity=Product.class)
#JoinColumn(name = "product_id")
#Getter
#Setter
private Product product;
//...
^I have commented optional=false otherwise I get a 500 error because of the product being null
#Entity
#Table(name="products")
public class Product {
#Id
#GeneratedValue
#Column(name="product_id")
private Long id;
//...
// #OneToMany(mappedBy = "product", cascade = CascadeType.ALL, orphanRemoval = true)
// private List<OrderDetail> orderDetailList;
//...
}
^ I have tried adding or not adding this side of the relationship, none works; I think I should not need it anyways because I interact with my detail's product and not with my product's details.
And here is my Postman POST Request to /orders:
{
"address": "Dorton Road 80",
"email": "tsayb#opera.com",
"tel": "[phone]",
"schedule": "21:00",
"orderDetailList": [
{ "product_id": 1,
"quantity": 1 },
{ "product_id": 2,
"quantity": 1 }]
}
Which returns
{
"address": "Dorton Road 80",
"email": "tsayb#opera.com",
"tel": "[phone]",
"schedule": "21:00",
"orderDetailList": [
{
"quantity": 1,
"product": null
},
{
"quantity": 1,
"product": null
}
]
}
Note that products are null, but my products id 1 and 2 do exist in the products crud. Why are them not being saved(or returned) ?
Thank you very much for your time.

Answer 1

each OrderDetail holds an id of one Product (products can be repeated, therefore it should be ManyToOne).
I think you are right. Many orderDetail to One product.
Could you check in the database to see if the product_id is inserted into the order_details table? Note that "saved, not fetched" and "not saved, not fetched" are two problems.
Could you add fetch = FetchType.EAGER in the #ManyToOne and #OneToMany annotations to make sure that they are fetched eagerly?
Besides, it is not relevant to your question, but plural forms are conventionally forbidden as table names such as products.