Spring Boot: Found shared references to a collection error - mysql

Question

I'm trying to build a small Spring Boot CRUD app with some basic e-commerce functionality (i.e. add to cart, etc.). My Basic entities are customer, cheese, roles and orders.
Customer's have a many-to-many relationship with Cheese (the fictional object I'm selling) objects. In addition, Orders have a many-to-many relationship with Cheese objects. When my customer checks out, I am intending to transfer the cart contents (i.e. the list of Cheeses) to the Order object, along with customer id, total price, etc. I want the "Orders" to be able to be logged by myself, as well as to provide an order history for the customer. The instantiating of the order object with customer.getCheeses() is what is giving me the shared collection error.
I can somewhat get around this by creating new Cheese items, however, that messes up my database, creating duplicates upon every new order.
The processing of orders is done in the completeOrder() function in UserController. All of the html/thymeleaf seems to be working - I can post it if it will help.
Cheese
package com.example.demo.models;
import javax.persistence.*;
import javax.validation.constraints.DecimalMax;
import javax.validation.constraints.DecimalMin;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
#Entity
public class Cheese {
#NotNull
#Size(min=2, max=20)
private String name;
#NotNull
#Size(min=2, max=20)
private String description;
#NotNull
#DecimalMax("10000.0") #DecimalMin("0.0")
private BigDecimal price;
#Id
#GeneratedValue
private int id;
#ManyToMany(mappedBy = "cheeses")
private List<Customer> customers = new ArrayList<>();
#ManyToMany(mappedBy = "cheeses")
private List<Orders> orders = new ArrayList<>();
public Cheese() {}
public Cheese(String name, String description, BigDecimal price) {
this.name = name;
this.description = description;
this.price = price;
}
public BigDecimal getPrice() {
return price;
}
public void setPrice(BigDecimal price) {
this.price = price;
}
public int getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public List<Orders> getOrders() {
return orders;
}
public void setOrders(List<Orders> orders) {
this.orders = orders;
}
}
Customer
package com.example.demo.models;
import javax.persistence.*;
import javax.validation.constraints.Email;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import java.io.Serializable;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
#Entity
public class Customer implements Serializable {
#NotNull
#Size(min = 2, max = 25)
private String name;
#GeneratedValue
#Id
private int accountNumber;
private BigDecimal accountFunds;
#NotNull
#Size(min = 2)
private String password;
#NotNull
#Size(min = 2, max = 25)
#Email
private String email;
#ManyToMany(cascade=CascadeType.ALL)
#JoinTable(name="user_roles",
joinColumns={#JoinColumn(name="CUSTOMER_EMAIL", referencedColumnName = "email")},
inverseJoinColumns={#JoinColumn(name="ROLE_ID", referencedColumnName="id")})
private List<Role> roles;
//#ElementCollection
#ManyToMany(cascade=CascadeType.ALL)
#JoinTable(name="cheese_customers",
joinColumns={#JoinColumn(name="CUSTOMER_ID", referencedColumnName = "accountNumber")},
inverseJoinColumns={#JoinColumn(name="PRODUCT_ID", referencedColumnName="id")})
private List<Cheese> cheeses = new ArrayList<>();
public Customer(String name, String password, String email) {
this.name = name;
this.password = password;
this.email = email;
this.accountFunds = new BigDecimal(225.00);
}
public Customer() {}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAccountNumber() {
return accountNumber;
}
public List<Role> getRoles() {
return roles;
}
public void setRoles(List<Role> roles) {
this.roles = roles;
}
public BigDecimal getAccountFunds() {
return accountFunds;
}
public void setAccountFunds(BigDecimal accountFunds) {
this.accountFunds = accountFunds;
}
public List<Cheese> getCheeses() {
return cheeses;
}
public void setCheeses(List<Cheese> cheeses) {
this.cheeses = cheeses;
}
}
Orders
package com.example.demo.models;
import javax.persistence.*;
import java.math.BigDecimal;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
#Entity
public class Orders {
#GeneratedValue
#Id
private int orderId;
#ManyToMany(cascade= CascadeType.ALL)
#JoinTable(name="customer_orders",
joinColumns={#JoinColumn(name="ORDER_ID", referencedColumnName = "orderId")},
inverseJoinColumns={#JoinColumn(name="PRODUCT_ID", referencedColumnName="id")})
private List<Cheese> cheeses = new ArrayList<>();
private int customerId;
private BigDecimal totalPrice;
private Date date;
public Orders() {}
public Orders(List<Cheese> cheeses, int customerId, BigDecimal totalPrice) {
this.cheeses = cheeses;
this.customerId = customerId;
this.totalPrice = totalPrice;
this.date = new Date();
}
private String getFormattedDate() {
DateFormat format = new SimpleDateFormat("yyyy-MM-dd");
return format.format(this.date);
}
public int getOrderId() {
return orderId;
}
public List<Cheese> getCheeses() {
return cheeses;
}
public void setCheeses(List<Cheese> cheeses) {
this.cheeses = cheeses;
}
public int getCustomerId() {
return customerId;
}
public void setCustomerId(int customerId) {
this.customerId = customerId;
}
public BigDecimal getTotalPrice() {
return totalPrice;
}
public void setTotalPrice(BigDecimal totalPrice) {
this.totalPrice = totalPrice;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
}
UserController
package com.example.demo.controllers;
import com.example.demo.models.Customer;
import com.example.demo.models.Orders;
import com.example.demo.models.data.CheeseDao;
import com.example.demo.models.data.CustomerDao;
import com.example.demo.models.data.OrdersDAO;
import com.example.demo.models.services.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.Errors;
import org.springframework.web.bind.annotation.*;
import java.math.BigDecimal;
import java.util.List;
#Controller
#RequestMapping("cheese")
public class UserController {
#Autowired
private CustomerDao customerDao;
#Autowired
UserService userService;
#Autowired
CheeseDao cheeseDao;
#Autowired
OrdersDAO ordersDAO;
#RequestMapping(value = "login")
public String loginPage(Model model) {
model.addAttribute("title", "Login Page");
model.addAttribute("customer", new Customer());
return "cheese/login";
}
#RequestMapping(value = "account")
public String accountInfo(Model model) {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
Customer customer = customerDao.findByEmail(authentication.getName());
model.addAttribute("name", customer.getName());
model.addAttribute("funds", customer.getAccountFunds());
model.addAttribute("customer", customer);
model.addAttribute("cheeses", customer.getCheeses());
model.addAttribute("total", userService.getCartTotal(customer));
return "cheese/account";
}
#PostMapping(value = "account")
public String removeItem(#RequestParam int cheeseId) {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
Customer customer = customerDao.findByEmail(authentication.getName());
if (customer.getCheeses().contains(cheeseDao.getCheeseById(cheeseId))) {
customer.getCheeses().remove(cheeseDao.getCheeseById(cheeseId));
}
customerDao.save(customer);
return "redirect:/cheese/account";
}
#RequestMapping(value = "checkout")
public String orderCheckout(Model model) {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
Customer customer = customerDao.findByEmail(authentication.getName());
model.addAttribute("cheeses", customer.getCheeses());
model.addAttribute("total", userService.getCartTotal(customer));
return "cheese/checkout";
}
#GetMapping("signup")
public String displaySignUpForm(Model model) {
model.addAttribute("title", "Sign Up");
model.addAttribute("customer", new Customer());
return "cheese/signup";
}
#PostMapping(value = "signup")
public String processSignUp(Model model, #ModelAttribute Customer customer, Errors errors) {
if (errors.hasErrors()) {
return "cheese/signup";
}
userService.createUser(customer);
return "cheese/success";
}
#GetMapping("ordersuccess")
public String showForm() {
return "cheese/ordersuccess";
}
#PostMapping("checkout")
public String completeOrder() {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
Customer customer = customerDao.findByEmail(authentication.getName());
double accountFunds = customer.getAccountFunds().doubleValue();
double cartTotal = userService.getCartTotal(customer).doubleValue();
if (accountFunds >= cartTotal) {
accountFunds = accountFunds - cartTotal;
customer.setAccountFunds(new BigDecimal(accountFunds));
Orders order = new Orders(customer.getCheeses(), customer.getAccountNumber(), new BigDecimal(cartTotal));
customer.getCheeses().clear();
customerDao.save(customer);
ordersDAO.save(order);
return "redirect:/cheese/ordersuccess";
}
return "redirect:cheese/checkout";
}
#GetMapping("orders")
public String viewOrderHistory(Model model) {
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
Customer customer = customerDao.findByEmail(authentication.getName());
List<Orders> orders = ordersDAO.findOrdersByCustomerId(customer.getAccountNumber());
model.addAttribute("orders", orders);
return "cheese/orders";
}
}

Answer 1

So what you are trying to do is fetch and fill the cheese collection when you get a customer? Normally, in order to do that, you must set lazy loading to false, otherwise the session closes before you can fetch the collection.
To be able to load the customer with it's cheese collection, you must got to your Hibernate query and use a "join fetch" command. Something like this.
sessionFactory.getCurrentSession().createQuery("from Customer C join fetch C.cheeses").list();
This will force the query to fetch the cheese collection before the session closes. Also, one more thing, normally I would use a Set to avoid duplicates in the collection. I hope this helps.