[Spring Boot Basics] Quan hệ giữa các entity trong JPA: @OneToOne, @OneToMany, @ManyToOne, @ManyToMany, cascade và FetchType

package com.example.demo.product;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "categories")
public class Category {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @Column(nullable = false, unique = true)
    private String name;
 
    protected Category() {
    }
 
    public Category(String name) {
        this.name = name;
    }
 
    public Long getId() {
        return id;
    }
 
    public String getName() {
        return name;
    }
}

package com.example.demo.product;
 
import java.math.BigDecimal;
import java.util.ArrayList; 
import java.util.List; 
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.JoinColumn; 
import jakarta.persistence.JoinTable; 
import jakarta.persistence.ManyToMany; 
import jakarta.persistence.ManyToOne; 
import jakarta.persistence.Table;
 
@Entity
@Table(name = "products")
public class Product {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @Column(nullable = false)
    private String name;
 
    @Column(nullable = false, unique = true)
    private String sku;
 
    @Column(nullable = false, precision = 12, scale = 2)
    private BigDecimal price;
 
    @Column(nullable = false)
    private int stock;
 
    private String category; 
    @ManyToOne
    @JoinColumn(name = "category_id") 
    private Category category; 
 
    @ManyToMany
    @JoinTable(name = "product_tags", 
            joinColumns = @JoinColumn(name = "product_id"), 
            inverseJoinColumns = @JoinColumn(name = "tag_id")) 
    private List<Tag> tags = new ArrayList<>(); 
 
    protected Product() {
    }
 
    public Product(String name, String sku, BigDecimal price, int stock, String category) { 
    public Product(String name, String sku, BigDecimal price, int stock, Category category) { 
        this.name = name;
        this.sku = sku;
        this.price = price;
        this.stock = stock;
        this.category = category;
    }
 
    // getters for id, name, sku, price and stock, and setStock(int)
 
    public String getCategory() { 
    public Category getCategory() { 
        return category;
    }
 
    public List<Tag> getTags() { 
        return tags; 
    } 
}

package com.example.demo.product;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "tags")
public class Tag {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @Column(nullable = false, unique = true)
    private String name;
 
    protected Tag() {
    }
 
    public Tag(String name) {
        this.name = name;
    }
 
    public Long getId() {
        return id;
    }
 
    public String getName() {
        return name;
    }
}

package com.example.demo.order;
 
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
 
import com.example.demo.customer.Customer;
 
import jakarta.persistence.CascadeType;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.JoinColumn;
import jakarta.persistence.ManyToOne;
import jakarta.persistence.OneToMany;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "orders")
public class Order {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @ManyToOne
    @JoinColumn(name = "customer_id")
    private Customer customer;
 
    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL)
    private List<OrderLine> lines = new ArrayList<>();
 
    protected Order() {
    }
 
    public Order(Customer customer) {
        this.customer = customer;
    }
 
    public BigDecimal total() {
        return lines.stream()
                .map(OrderLine::lineTotal)
                .reduce(BigDecimal.ZERO, BigDecimal::add);
    }
 
    public Long getId() {
        return id;
    }
 
    public Customer getCustomer() {
        return customer;
    }
 
    public List<OrderLine> getLines() {
        return lines;
    }
}

package com.example.demo.order;
 
import java.math.BigDecimal;
 
import com.example.demo.product.Product;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.JoinColumn;
import jakarta.persistence.ManyToOne;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "order_lines")
public class OrderLine {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @ManyToOne
    @JoinColumn(name = "order_id")
    private Order order;
 
    @ManyToOne
    @JoinColumn(name = "product_id")
    private Product product;
 
    @Column(nullable = false)
    private int quantity;
 
    @Column(nullable = false, precision = 12, scale = 2)
    private BigDecimal unitPrice;
 
    protected OrderLine() {
    }
 
    public OrderLine(Product product, int quantity) {
        this.product = product;
        this.quantity = quantity;
        this.unitPrice = product.getPrice();
    }
 
    public BigDecimal lineTotal() {
        return unitPrice.multiply(BigDecimal.valueOf(quantity));
    }
 
    void setOrder(Order order) {
        this.order = order;
    }
 
    // getters for id, order, product, quantity and unitPrice
}

package com.example.demo.customer;
 
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.JoinColumn;
import jakarta.persistence.OneToOne;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "customer_profiles")
public class CustomerProfile {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @OneToOne
    @JoinColumn(name = "customer_id")
    private Customer customer;
 
    @Column(nullable = false)
    private String fullName;
 
    private String phone;
 
    protected CustomerProfile() {
    }
 
    public CustomerProfile(String fullName, String phone) {
        this.fullName = fullName;
        this.phone = phone;
    }
 
    void setCustomer(Customer customer) {
        this.customer = customer;
    }
 
    // getters for id, customer, fullName and phone
}

package com.example.demo.customer;
 
import jakarta.persistence.CascadeType;
import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.OneToOne;
import jakarta.persistence.Table;
 
@Entity
@Table(name = "customers")
public class Customer {
 
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
 
    @Column(nullable = false, unique = true)
    private String email;
 
    @OneToOne(mappedBy = "customer", cascade = CascadeType.ALL)
    private CustomerProfile profile;
 
    protected Customer() {
    }
 
    public Customer(String email) {
        this.email = email;
    }
 
    public void setProfile(CustomerProfile profile) {
        this.profile = profile;
        profile.setCustomer(this);
    }
 
    // getters for id, email and profile
}

spring.application.name=demo
logging.level.org.hibernate.SQL=debug

spring.datasource.url=jdbc:postgresql://localhost:55428/shop
spring.datasource.username=shop
spring.datasource.password=secret
spring.jpa.hibernate.ddl-auto=create

docker run -d --name sb-a28-pg -e POSTGRES_USER=shop -e POSTGRES_PASSWORD=secret -e POSTGRES_DB=shop -p 55428:5432 postgres:18

./gradlew -q bootJar

java -jar build/libs/demo-0.0.1-SNAPSHOT.jar --spring.profiles.active=postgres --server.port=8128

docker exec sb-a28-pg psql -U shop -d shop -c '\d products'

create table products (
    price numeric(12,2) not null,
    stock integer not null,
    category_id bigint,
    id bigint generated by default as identity,
    name varchar(255) not null,
    sku varchar(255) not null unique,
    primary key (id)
)
 
alter table if exists products add constraint FKog2rp4qthbtt2lfyhfo32lsw9 foreign key (category_id) references categories

                                    Table "public.products"
   Column    |          Type          | Collation | Nullable |             Default
-------------+------------------------+-----------+----------+----------------------------------
 price       | numeric(12,2)          |           | not null |
 stock       | integer                |           | not null |
 category_id | bigint                 |           |          |
 id          | bigint                 |           | not null | generated by default as identity
 name        | character varying(255) |           | not null |
 sku         | character varying(255) |           | not null |
Indexes:
    "products_pkey" PRIMARY KEY, btree (id)
    "products_sku_key" UNIQUE CONSTRAINT, btree (sku)
Foreign-key constraints:
    "fkog2rp4qthbtt2lfyhfo32lsw9" FOREIGN KEY (category_id) REFERENCES categories(id)
Referenced by:
    TABLE "product_tags" CONSTRAINT "fk5rk6s19k3risy7q7wqdr41uss" FOREIGN KEY (product_id) REFERENCES products(id)
    TABLE "order_lines" CONSTRAINT "fk5v1oeejtgtf2n3toppm3tkuhh" FOREIGN KEY (product_id) REFERENCES products(id)

create table customer_profiles (
    customer_id bigint unique,
    id bigint generated by default as identity,
    full_name varchar(255) not null,
    phone varchar(255),
    primary key (id)
)
 
alter table if exists customer_profiles add constraint FKnjy1dugyof18fa21tu22fu98j foreign key (customer_id) references customers

                                Table "public.customer_profiles"
   Column    |          Type          | Collation | Nullable |             Default
-------------+------------------------+-----------+----------+----------------------------------
 customer_id | bigint                 |           |          |
 id          | bigint                 |           | not null | generated by default as identity
 full_name   | character varying(255) |           | not null |
 phone       | character varying(255) |           |          |
Indexes:
    "customer_profiles_pkey" PRIMARY KEY, btree (id)
    "customer_profiles_customer_id_key" UNIQUE CONSTRAINT, btree (customer_id)
Foreign-key constraints:
    "fknjy1dugyof18fa21tu22fu98j" FOREIGN KEY (customer_id) REFERENCES customers(id)

                                 Table "public.customers"
 Column |          Type          | Collation | Nullable |             Default
--------+------------------------+-----------+----------+----------------------------------
 id     | bigint                 |           | not null | generated by default as identity
 email  | character varying(255) |           | not null |
Indexes:
    "customers_pkey" PRIMARY KEY, btree (id)
    "customers_email_key" UNIQUE CONSTRAINT, btree (email)
Referenced by:
    TABLE "customer_profiles" CONSTRAINT "fknjy1dugyof18fa21tu22fu98j" FOREIGN KEY (customer_id) REFERENCES customers(id)
    TABLE "orders" CONSTRAINT "fkpxtb8awmi0dk6smoh2vp1litg" FOREIGN KEY (customer_id) REFERENCES customers(id)

create table product_tags (
    product_id bigint not null,
    tag_id bigint not null
)
 
alter table if exists product_tags add constraint FKpur2885qb9ae6fiquu77tcv1o foreign key (tag_id) references tags
alter table if exists product_tags add constraint FK5rk6s19k3risy7q7wqdr41uss foreign key (product_id) references products

             Table "public.product_tags"
   Column   |  Type  | Collation | Nullable | Default
------------+--------+-----------+----------+---------
 product_id | bigint |           | not null |
 tag_id     | bigint |           | not null |
Foreign-key constraints:
    "fk5rk6s19k3risy7q7wqdr41uss" FOREIGN KEY (product_id) REFERENCES products(id)
    "fkpur2885qb9ae6fiquu77tcv1o" FOREIGN KEY (tag_id) REFERENCES tags(id)

    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL) 
    @OneToMany(cascade = CascadeType.ALL) 
    private List<OrderLine> lines = new ArrayList<>();

    @ManyToOne
    @JoinColumn(name = "order_id") 
    private Order order; 

               List of tables
 Schema |       Name        | Type  | Owner
--------+-------------------+-------+-------
 public | categories        | table | shop
 public | customer_profiles | table | shop
 public | customers         | table | shop
 public | order_lines       | table | shop
 public | orders            | table | shop
 public | orders_lines      | table | shop
 public | product_tags      | table | shop
 public | products          | table | shop
 public | tags              | table | shop
(9 rows)

create table orders_lines (
    lines_id bigint not null unique,
    order_id bigint not null
)
 
alter table if exists orders_lines add constraint FK6odyxaaebqswyy8yhp9wtfsn4 foreign key (lines_id) references order_lines
alter table if exists orders_lines add constraint FKahmp9mk9umvxbsm32o7m2pt5q foreign key (order_id) references orders

                              Table "public.order_lines"
   Column   |     Type      | Collation | Nullable |             Default
------------+---------------+-----------+----------+----------------------------------
 quantity   | integer       |           | not null |
 unit_price | numeric(12,2) |           | not null |
 id         | bigint        |           | not null | generated by default as identity
 product_id | bigint        |           |          |
Indexes:
    "order_lines_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "fk5v1oeejtgtf2n3toppm3tkuhh" FOREIGN KEY (product_id) REFERENCES products(id)
Referenced by:
    TABLE "orders_lines" CONSTRAINT "fk6odyxaaebqswyy8yhp9wtfsn4" FOREIGN KEY (lines_id) REFERENCES order_lines(id)

Order order = new Order(customer);
order.getLines().add(new OrderLine(keyboard, 1));
order.getLines().add(new OrderLine(mouse, 2));
orderRepository.save(order);

insert into orders (customer_id,id) values (?,default)
insert into order_lines (product_id,quantity,unit_price,id) values (?,?,?,default)
insert into order_lines (product_id,quantity,unit_price,id) values (?,?,?,default)
insert into orders_lines (order_id,lines_id) values (?,?)
insert into orders_lines (order_id,lines_id) values (?,?)

Order order = new Order(customer);
OrderLine line = new OrderLine(keyboard, 1);
order.getLines().add(line);
orderRepository.save(order);

insert into orders (customer_id,id) values (?,default)
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)

jdbcTemplate.queryForList("select id, order_id, product_id, quantity from order_lines where id = (select max(id) from order_lines)");

[{ID=23, ORDER_ID=null, PRODUCT_ID=1, QUANTITY=1}]

org.springframework.dao.DataIntegrityViolationException: could not execute statement [NULL not allowed for column "ORDER_ID"; SQL statement:
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default) [23502-240]] [insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)]; SQL [insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)]; constraint [ORDER_ID]

    public Order(Customer customer) {
        this.customer = customer;
    }
 
    public void addLine(OrderLine line) { 
        lines.add(line); 
        line.setOrder(this); 
    } 
 
    public void removeLine(OrderLine line) { 
        lines.remove(line); 
        line.setOrder(null); 
    } 
 
    public BigDecimal total() {

Order order = new Order(customer);
order.addLine(new OrderLine(keyboard, 1));
order.addLine(new OrderLine(mouse, 2));
orderRepository.save(order);

insert into orders (customer_id,id) values (?,default)
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)

select p1_0.id,c1_0.id,c1_0.name,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 left join categories c1_0 on c1_0.id=p1_0.category_id where p1_0.id=?

select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0
select c1_0.id,c1_0.name from categories c1_0 where c1_0.id=?
select c1_0.id,c1_0.name from categories c1_0 where c1_0.id=?
select c1_0.id,c1_0.name from categories c1_0 where c1_0.id=?

select o1_0.id,c1_0.id,c1_0.email,p1_0.id,p1_0.full_name,p1_0.phone from orders o1_0 left join customers c1_0 on c1_0.id=o1_0.customer_id left join customer_profiles p1_0 on c1_0.id=p1_0.customer_id where o1_0.id=?
select l1_0.order_id,l1_0.id,p1_0.id,c1_0.id,c1_0.name,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock,l1_0.quantity,l1_0.unit_price from order_lines l1_0 left join products p1_0 on p1_0.id=l1_0.product_id left join categories c1_0 on c1_0.id=p1_0.category_id where l1_0.order_id=?

    @ManyToOne
    @JoinColumn(name = "category_id") 
    @ManyToOne(fetch = FetchType.LAZY, optional = false) 
    @JoinColumn(name = "category_id", nullable = false) 
    private Category category;

    @ManyToOne
    @JoinColumn(name = "order_id") 
    @ManyToOne(fetch = FetchType.LAZY, optional = false) 
    @JoinColumn(name = "order_id", nullable = false) 
    private Order order;
 
    @ManyToOne
    @JoinColumn(name = "product_id") 
    @ManyToOne(fetch = FetchType.LAZY, optional = false) 
    @JoinColumn(name = "product_id", nullable = false) 
    private Product product;

    @OneToOne
    @JoinColumn(name = "customer_id") 
    @OneToOne(fetch = FetchType.LAZY, optional = false) 
    @JoinColumn(name = "customer_id", nullable = false) 
    private Customer customer;

    @OneToOne(mappedBy = "customer", cascade = CascadeType.ALL) 
    @OneToOne(mappedBy = "customer", cascade = CascadeType.ALL, fetch = FetchType.LAZY) 
    private CustomerProfile profile;

 category_id | bigint                 |           | not null |

select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where p1_0.id=?
select c1_0.id,c1_0.name from categories c1_0 where c1_0.id=?

Product keyboard = productRepository.findById(1L).orElseThrow();
Tag rgb = tagRepository.findByName("rgb").orElseThrow();
keyboard.getTags().remove(rgb);

delete from product_tags where product_id=?
insert into product_tags (product_id,tag_id) values (?,?)
insert into product_tags (product_id,tag_id) values (?,?)

import java.math.BigDecimal;
import java.util.ArrayList; 
import java.util.List; 
import java.util.HashSet; 
import java.util.Set; 
 
// ...
 
    @ManyToMany
    @JoinTable(name = "product_tags",
            joinColumns = @JoinColumn(name = "product_id"),
            inverseJoinColumns = @JoinColumn(name = "tag_id"))
    private List<Tag> tags = new ArrayList<>(); 
    private Set<Tag> tags = new HashSet<>(); 
 
// ...
 
    public List<Tag> getTags() { 
    public Set<Tag> getTags() { 
        return tags;
    }

delete from product_tags where product_id=? and tag_id=?

             Table "public.product_tags"
   Column   |  Type  | Collation | Nullable | Default
------------+--------+-----------+----------+---------
 product_id | bigint |           | not null |
 tag_id     | bigint |           | not null |
Indexes:
    "product_tags_pkey" PRIMARY KEY, btree (product_id, tag_id)
Foreign-key constraints:
    "fk5rk6s19k3risy7q7wqdr41uss" FOREIGN KEY (product_id) REFERENCES products(id)
    "fkpur2885qb9ae6fiquu77tcv1o" FOREIGN KEY (tag_id) REFERENCES tags(id)

    @Query("select o from Order o left join fetch o.lines l left join fetch l.product p left join fetch p.tags")
    List<Order> findAllWithLinesAndTags();

org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags: [com.example.demo.product.Product.tags, com.example.demo.order.Order.lines]

select o1_0.id,o1_0.customer_id,l1_0.order_id,l1_0.id,l1_0.product_id,p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock,t1_0.product_id,t1_1.id,t1_1.name,l1_0.quantity,l1_0.unit_price from orders o1_0 left join order_lines l1_0 on o1_0.id=l1_0.order_id left join products p1_0 on p1_0.id=l1_0.product_id left join product_tags t1_0 on p1_0.id=t1_0.product_id left join tags t1_1 on t1_1.id=t1_0.tag_id

package com.example.demo.order;
 
import java.util.List;
 
import com.example.demo.customer.Customer;
import com.example.demo.customer.CustomerNotFoundException;
import com.example.demo.customer.CustomerRepository;
import com.example.demo.product.Product;
import com.example.demo.product.ProductService;
 
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
 
@Service
public class OrderService {
 
    private final OrderRepository orders;
    private final CustomerRepository customers;
    private final ProductService productService;
 
    public OrderService(OrderRepository orders, CustomerRepository customers, ProductService productService) {
        this.orders = orders;
        this.customers = customers;
        this.productService = productService;
    }
 
    @Transactional
    public Order place(Long customerId, List<OrderItem> items) {
        Customer customer = customers.findById(customerId)
                .orElseThrow(() -> new CustomerNotFoundException(customerId));
        Order order = new Order(customer);
        for (OrderItem item : items) {
            Product product = productService.reserveStock(item.productId(), item.quantity());
            order.addLine(new OrderLine(product, item.quantity()));
        }
        return orders.save(order);
    }
 
    @Transactional(readOnly = true)
    public Order findById(Long id) {
        return orders.findById(id).orElseThrow(() -> new OrderNotFoundException(id));
    }
 
    @Transactional(readOnly = true)
    public List<Order> findAll() {
        return orders.findAll();
    }
}

package com.example.demo.order;
 
public record OrderItem(Long productId, int quantity) {
}

    public Product reserveStock(Long id, int quantity) {
        Product product = findById(id);
        if (product.getStock() < quantity) {
            throw new InsufficientStockException(product.getSku(), product.getStock(), quantity);
        }
        product.setStock(product.getStock() - quantity);
        return product;
    }

select c1_0.id,c1_0.email from customers c1_0 where c1_0.id=?
select cp1_0.id,cp1_0.customer_id,cp1_0.full_name,cp1_0.phone from customer_profiles cp1_0 where cp1_0.customer_id=?
select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where p1_0.id=?
select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where p1_0.id=?
insert into orders (customer_id,id) values (?,default)
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)
insert into order_lines (order_id,product_id,quantity,unit_price,id) values (?,?,?,?,default)
update products set category_id=?,name=?,price=?,sku=?,stock=? where id=?
update products set category_id=?,name=?,price=?,sku=?,stock=? where id=?

    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL) 
    @OneToMany(mappedBy = "order") 
    private List<OrderLine> lines = new ArrayList<>();

insert into orders (customer_id,id) values (?,default)

Order order = orderRepository.findById(1L).orElseThrow();
OrderLine first = order.getLines().get(0);
order.removeLine(first);
entityManager.flush();

update order_lines set order_id=?,product_id=?,quantity=?,unit_price=? where id=?

org.hibernate.exception.ConstraintViolationException: could not execute statement [NULL not allowed for column "ORDER_ID"; SQL statement:
update order_lines set order_id=?,product_id=?,quantity=?,unit_price=? where id=? [23502-240]] [update order_lines set order_id=?,product_id=?,quantity=?,unit_price=? where id=?]

    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL) 
    @OneToMany(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true) 
    private List<OrderLine> lines = new ArrayList<>();

delete from order_lines where id=?

    @ManyToOne(fetch = FetchType.LAZY, optional = false) 
    @ManyToOne(fetch = FetchType.LAZY, optional = false, cascade = CascadeType.ALL) 
    @JoinColumn(name = "category_id", nullable = false)
    private Category category;
 
    @ManyToMany
    @ManyToMany(cascade = CascadeType.ALL) 
    @JoinTable(name = "product_tags",

select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where p1_0.id=?
select t1_0.product_id,t1_1.id,t1_1.name from product_tags t1_0 join tags t1_1 on t1_1.id=t1_0.tag_id where t1_0.product_id=?
select c1_0.id,c1_0.name from categories c1_0 where c1_0.id=?
delete from product_tags where product_id=?
delete from tags where id=?
delete from products where id=?
delete from categories where id=?

categories: [Keyboards, Mice, Accessories, Webcams]
tags: [wireless, bestseller, usb-c, rgb, mechanical, streaming]

categories: [Keyboards, Mice, Accessories]
tags: [wireless, bestseller, usb-c, rgb, mechanical]

delete from product_tags where product_id=?
delete from tags where id=?

org.springframework.dao.DataIntegrityViolationException: could not execute statement [Referential integrity constraint violation: "FKPUR2885QB9AE6FIQUU77TCV1O: PUBLIC.PRODUCT_TAGS FOREIGN KEY(TAG_ID) REFERENCES PUBLIC.TAGS(ID) (CAST(1 AS BIGINT))"; SQL statement:
delete from tags where id=? [23503-240]] [delete from tags where id=?]; SQL [delete from tags where id=?]; constraint [FKPUR2885QB9AE6FIQUU77TCV1O]

select p1_0.id,p1_0.category_id,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where p1_0.id=?
delete from product_tags where product_id=?
delete from products where id=?

select c1_0.id,c1_0.email from customers c1_0
select cp1_0.id,c1_0.id,c1_0.email,cp1_0.full_name,cp1_0.phone from customer_profiles cp1_0 left join customers c1_0 on c1_0.id=cp1_0.customer_id where cp1_0.customer_id=?
select cp1_0.id,c1_0.id,c1_0.email,cp1_0.full_name,cp1_0.phone from customer_profiles cp1_0 left join customers c1_0 on c1_0.id=cp1_0.customer_id where cp1_0.customer_id=?
select cp1_0.id,c1_0.id,c1_0.email,cp1_0.full_name,cp1_0.phone from customer_profiles cp1_0 left join customers c1_0 on c1_0.id=cp1_0.customer_id where cp1_0.customer_id=?

select c1_0.id,c1_0.email from customers c1_0 where c1_0.id=?
select cp1_0.id,cp1_0.customer_id,cp1_0.full_name,cp1_0.phone from customer_profiles cp1_0 where cp1_0.customer_id=?

package com.example.demo.order;
 
import java.util.List;
 
import jakarta.validation.Valid;
import jakarta.validation.constraints.NotEmpty;
import jakarta.validation.constraints.NotNull;
import jakarta.validation.constraints.Positive;
 
public record PlaceOrderRequest(@NotEmpty List<@Valid Line> lines) {
 
    public record Line(@NotNull Long productId, @NotNull @Positive Integer quantity) {
    }
}

package com.example.demo.order;
 
import java.math.BigDecimal;
import java.util.List;
 
public record OrderResponse(Long id, Long customerId, List<OrderLineResponse> lines, BigDecimal total) {
 
    public record OrderLineResponse(Long productId, int quantity, BigDecimal unitPrice, BigDecimal lineTotal) {
 
        static OrderLineResponse from(OrderLine line) {
            return new OrderLineResponse(line.getProduct().getId(), line.getQuantity(),
                    line.getUnitPrice(), line.lineTotal());
        }
    }
 
    public static OrderResponse from(Order order) {
        return new OrderResponse(order.getId(), order.getCustomer().getId(),
                order.getLines().stream().map(OrderLineResponse::from).toList(), order.total());
    }
}

package com.example.demo.order;
 
import java.net.URI;
import java.util.List;
 
import jakarta.validation.Valid;
 
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
 
@RestController
public class OrderController {
 
    private final OrderService service;
 
    public OrderController(OrderService service) {
        this.service = service;
    }
 
    @PostMapping("/api/customers/{customerId}/orders")
    public ResponseEntity<OrderResponse> place(@PathVariable Long customerId,
                                               @Valid @RequestBody PlaceOrderRequest request) {
        List<OrderItem> items = request.lines().stream()
                .map(line -> new OrderItem(line.productId(), line.quantity()))
                .toList();
        Order order = service.place(customerId, items);
        URI location = ServletUriComponentsBuilder.fromCurrentContextPath()
                .path("/api/orders/{id}")
                .buildAndExpand(order.getId())
                .toUri();
        return ResponseEntity.created(location).body(OrderResponse.from(order));
    }
 
    @GetMapping("/api/orders/{id}")
    public OrderResponse findById(@PathVariable Long id) {
        return OrderResponse.from(service.findById(id));
    }
 
    @GetMapping("/api/orders")
    public List<OrderResponse> findAll() {
        return service.findAll().stream().map(OrderResponse::from).toList();
    }
}

curl -s -i http://localhost:8128/api/orders/1

HTTP/1.1 500
Content-Type: application/json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:25:15 GMT
Connection: close
 
{"timestamp":"2026-09-13T09:25:15.863Z","status":500,"error":"Internal Server Error","path":"/api/orders/1"}

o.s.web.servlet.DispatcherServlet        : GET "/api/orders/1", parameters={}
o.s.orm.jpa.JpaTransactionManager        : Creating new transaction with name [com.example.demo.order.OrderService.findById]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly
o.s.orm.jpa.JpaTransactionManager        : Opened new EntityManager [SessionImpl(651741364<open>)] for JPA transaction
org.hibernate.SQL                        : select o1_0.id,o1_0.customer_id from orders o1_0 where o1_0.id=?
o.s.orm.jpa.JpaTransactionManager        : Committing JPA transaction on EntityManager [SessionImpl(651741364<open>)]
o.s.orm.jpa.JpaTransactionManager        : Closing JPA EntityManager after transaction
o.s.web.servlet.DispatcherServlet        : Failed to complete request: org.hibernate.LazyInitializationException: Cannot lazily initialize collection of role 'com.example.demo.order.Order.lines' with key '1' (no session)

org.hibernate.LazyInitializationException: Cannot lazily initialize collection of role 'com.example.demo.order.Order.lines' with key '1' (no session)
	at org.hibernate.collection.spi.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:664) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
	at org.hibernate.collection.spi.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:239) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
	at org.hibernate.collection.spi.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:624) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
	at org.hibernate.collection.spi.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
	at org.hibernate.collection.spi.PersistentBag.iterator(PersistentBag.java:419) ~[hibernate-core-7.4.5.Final.jar!/:7.4.5.Final]
	at com.example.demo.order.OrderResponse.from(OrderResponse.java:18) ~[!/:0.0.1-SNAPSHOT]
	at com.example.demo.order.OrderController.findById(OrderController.java:41) ~[!/:0.0.1-SNAPSHOT]

o.s.web.servlet.DispatcherServlet        : GET "/api/orders/1", parameters={}
o.j.s.OpenEntityManagerInViewInterceptor : Opening JPA EntityManager in OpenEntityManagerInViewInterceptor
o.s.orm.jpa.JpaTransactionManager        : Creating new transaction with name [com.example.demo.order.OrderService.findById]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly
org.hibernate.SQL                        : select o1_0.id,o1_0.customer_id from orders o1_0 where o1_0.id=?
o.s.orm.jpa.JpaTransactionManager        : Committing JPA transaction on EntityManager [SessionImpl(1177722833<open>)]
o.s.orm.jpa.JpaTransactionManager        : Not closing pre-bound JPA EntityManager after transaction
org.hibernate.SQL                        : select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
o.j.s.OpenEntityManagerInViewInterceptor : Closing JPA EntityManager in OpenEntityManagerInViewInterceptor
o.s.web.servlet.DispatcherServlet        : Completed 200 OK

    @EntityGraph(attributePaths = "lines")
    Optional<Order> findWithLinesById(Long id);

    @Transactional(readOnly = true)
    public Order findById(Long id) {
        return orders.findById(id).orElseThrow(() -> new OrderNotFoundException(id)); 
        return orders.findWithLinesById(id).orElseThrow(() -> new OrderNotFoundException(id)); 
    }

select o1_0.id,o1_0.customer_id,l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from orders o1_0 left join order_lines l1_0 on o1_0.id=l1_0.order_id where o1_0.id=?

select o1_0.id,o1_0.customer_id from orders o1_0
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?
select l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from order_lines l1_0 where l1_0.order_id=?

    @Query("select o from Order o left join fetch o.lines order by o.id")
    List<Order> findAllWithLines();

    @Transactional(readOnly = true)
    public List<Order> findAll() {
        return orders.findAll(); 
        return orders.findAllWithLines(); 
    }

select o1_0.id,o1_0.customer_id,l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from orders o1_0 left join order_lines l1_0 on o1_0.id=l1_0.order_id order by o1_0.id

package com.example.demo.order;
 
import java.util.List;
import java.util.Optional;
 
import org.springframework.data.jpa.repository.EntityGraph;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
 
public interface OrderRepository extends JpaRepository<Order, Long> {
 
    @Query("select o from Order o left join fetch o.lines order by o.id")
    List<Order> findAllWithLines();
 
    @Override
    @EntityGraph(attributePaths = "lines") 
    List<Order> findAll(); 
 
    @EntityGraph(attributePaths = "lines")
    Optional<Order> findWithLinesById(Long id);
}

select o1_0.id,o1_0.customer_id,l1_0.order_id,l1_0.id,l1_0.product_id,l1_0.quantity,l1_0.unit_price from orders o1_0 left join order_lines l1_0 on o1_0.id=l1_0.order_id

@GetMapping("/lab/orders/{id}/entity")
Order entity(@PathVariable Long id) {
    return service.findById(id);
}

curl -s -i http://localhost:8128/lab/orders/1/entity

HTTP/1.1 200
Content-Type: application/json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:25:12 GMT
 
{"customer":{"email":"an@example.com","hibernateLazyInitializer":{},"id":1,"profile":{"fullName":"Nguyen Van An","phone":"0901000001","customer":{"email":"an@example.com","hibernateLazyInitializer":{},"id":1,"profile":{"fullName":"Nguyen Van An","phone":"0901000001",

"phone":"0901000001","customer":{"email":"an@example.com","hibernateLazyInitializer":}}}}}}}}}}}}}

.w.s.m.s.DefaultHandlerExceptionResolver : Ignoring exception, response committed already: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Document nesting depth (501) exceeds the maximum allowed (500, from `StreamWriteConstraints.getMaxNestingDepth()`)
.w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Document nesting depth (501) exceeds the maximum allowed (500, from `StreamWriteConstraints.getMaxNestingDepth()`)]
o.s.web.servlet.DispatcherServlet        : Completed 200 OK

.w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Could not initialize proxy [com.example.demo.customer.Customer#1] - no session]

curl -s -i http://localhost:8128/api/orders/1

HTTP/1.1 200
Content-Type: application/json
Content-Length: 178
Date: Sun, 13 Sep 2026 09:25:19 GMT
 
{"id":1,"customerId":1,"lines":[{"productId":1,"quantity":1,"unitPrice":89.90,"lineTotal":89.90},{"productId":2,"quantity":2,"unitPrice":24.50,"lineTotal":49.00}],"total":138.90}

curl -s -i -H 'Content-Type: application/json' -d '{"lines":[{"productId":1,"quantity":1},{"productId":2,"quantity":2}]}' http://localhost:8128/api/customers/1/orders

HTTP/1.1 201
Location: http://localhost:8128/api/orders/11
Content-Type: application/json
Transfer-Encoding: chunked
Date: Sun, 13 Sep 2026 09:25:19 GMT
 
{"id":11,"customerId":1,"lines":[{"productId":1,"quantity":1,"unitPrice":89.90,"lineTotal":89.90},{"productId":2,"quantity":2,"unitPrice":24.50,"lineTotal":49.00}],"total":138.90}