Java Community | Help. Code. Learn.•3y ago

What is an order in e-commerce application and how to control it. How is it related with user cart?

I'm training to create my first Food ordering from catering establishments application. I created administrator and his ability to add, edit and delete catering establishments - canteens, cafes, bars etc. Also to add various menu types and dishes into it. To edit it and to delete it. I have also created cart for users to add dishes from menus., edit quantity or to removes products from cart. But now I have to create an order. I kinda know what it is, but I don't know how exactly is it related with other entities. I know that each order should be for each user's cart at that exact time when he presses Checkout or order button. Then in the database there should be an order and all related information about the user and his ordered goods - dishes, quantities, price etc. What is relation between order and cart. For example my cart entity is this:

@Entity
@Table(name="cart_items")
public class CartItem {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    
    @ManyToOne
    @JoinColumn(name = "dish_id")
    private Dish dish;
    
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;
    
    private Integer quantity;
    
    public CartItem() {}

    public CartItem(Dish dish, User user, Integer quantity) {
        super();
        this.dish = dish;
        this.user = user;
        this.quantity = quantity;
    }

@Entity
@Table(name="cart_items")
public class CartItem {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    
    @ManyToOne
    @JoinColumn(name = "dish_id")
    private Dish dish;
    
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;
    
    private Integer quantity;
    
    public CartItem() {}

    public CartItem(Dish dish, User user, Integer quantity) {
        super();
        this.dish = dish;
        this.user = user;
        this.quantity = quantity;
    }

Manager or admin should be able to confirm or cancel the order. I think for the order I will use enum with values such as submitted, approved, withdrawn

21 Replies

JavaBot•3y ago

Hey, @Tomasm21! Please remember to /close this post once your question has been answered!

Tomasm21OP•3y ago

I don't want to reveal User object information that contains password. I will have to use intermediate DTO. But my main question is how to define an order. With what entities it should be related and what is relation type and why? I think that only with CartItem. But I'm not sure. There can be many cart items in an order. So I guess relation should be one-to-many. Or maybe in cart item there should be Many-to-one relation with Order class, I'm not sure about it.

imp_o_rt•3y ago

If you think about it, a cart sort of gets converted into an order. When you shop online you check out the cart which then becomes an order (with an id, line items etc). At that point the cart ceases to exist and you now have an order instead

Tomasm21OP•3y ago

So it's different class then which has additional fields like its own id, date, status( enum which can be - submitted, approved, withdrawn) and all info from CartItem - products, user info. Is it additional class OrderDetails? Or in the same order class? Then Order should not have any link to cart. But CartItemTransferDTO has all required data to make and Order

imp_o_rt•3y ago

Well you can sort of make the order the cart If it's checked out it's an order. If not, cart When it's checked out you can add extra info (method of payment, checkout time etc)

Tomasm21OP•3y ago

And then CartItemDAO entries for this user deleted.

imp_o_rt•3y ago

Well again you can just have an order item

Tomasm21OP•3y ago

User then sees not cart info, but an order which looks different than Admin or manager What is an order item? A class or a property(field) in CartItem?

imp_o_rt•3y ago

An order has many order items (aka line items) The cart contents essentially The product, quantity, maybe other stuff? Can't think of any other stuff

Tomasm21OP•3y ago

So order is a different class entity right?

imp_o_rt•3y ago

Yeah.

Order
- items: List<OrderItem>
- checkedOut: boolean

Order
- items: List<OrderItem>
- checkedOut: boolean

Some other stuff?

OrderItem
- product: Product
- quantity: int

OrderItem
- product: Product
- quantity: int

Tomasm21OP•3y ago

items: List<CartItem>

imp_o_rt•3y ago

That's ok too That's how I'd do it anyway It's got some caveats eg making sure only one non-checked-out order per user (which would be their cart)

Tomasm21OP•3y ago

alright. thanks for info checking message so the post would not be locked...

Unknown User•3y ago

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Tomasm21OP•3y ago

@Andrew Something is not right with my order that is created out of user's cart. The problem is that the database cannot create correct foreign key between Orders ID and Order Items entity field. The column ORDERS_ID at Item entity becomes null. And I think that it should be equal to the Order id for which those items belong to. Look at the picture of the database:

Tomasm21OP•3y ago

Tomasm21OP•3y ago

Something is not right. Maybe I defined entities properties JPA relations wrong. Check it out:

@Entity
public class Orders {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    
    @NotEmpty
    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime submitedAt;
    
    @NotEmpty
    private String orderName;
    
    @NotEmpty
    @Column(name="`User`")
    private String username;
    
    @Enumerated(EnumType.STRING)
    @Column
    private OrderStatus status;
    
    @OneToMany(mappedBy = "orders", cascade = { CascadeType.ALL}, fetch = FetchType.LAZY)
    private Set<Item> items;

@Entity
public class Orders {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    
    @NotEmpty
    @DateTimeFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private LocalDateTime submitedAt;
    
    @NotEmpty
    private String orderName;
    
    @NotEmpty
    @Column(name="`User`")
    private String username;
    
    @Enumerated(EnumType.STRING)
    @Column
    private OrderStatus status;
    
    @OneToMany(mappedBy = "orders", cascade = { CascadeType.ALL}, fetch = FetchType.LAZY)
    private Set<Item> items;

And the Item:

@Entity
public class Item {
    
    @Id
    private Integer id;
    
    @Column(name="`NAME`")
    private String dishName;
    
    @Column(name = "`DESCRIPTION`", length = 2000)
    private String dishDescription;
    
    @Column(name = "`QUANTITY`")
    private Integer quantityInCart;
    
    @Column(name = "`USER`")
    private String username;
    
    @ManyToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH, CascadeType.REFRESH })
    @JoinColumn(name = "ORDERS_ID")
    private Orders orders;

@Entity
public class Item {
    
    @Id
    private Integer id;
    
    @Column(name="`NAME`")
    private String dishName;
    
    @Column(name = "`DESCRIPTION`", length = 2000)
    private String dishDescription;
    
    @Column(name = "`QUANTITY`")
    private Integer quantityInCart;
    
    @Column(name = "`USER`")
    private String username;
    
    @ManyToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.DETACH, CascadeType.REFRESH })
    @JoinColumn(name = "ORDERS_ID")
    private Orders orders;

How to do entities relation correctly? Should it be one direction or two-directional relationship? What are differences of these relations? And what kind of relationship I should use? Why? I was doing JUnit tests for the Orders service methods. It turns out that it can create orders. And Order items from user's cart. But when it is time to show order (GetMapping) then it returns Orders entity with empty items set. Obviously it happens because JPA cannot find foreign key of items field for its designated order. It is null. Can you help me to solve this thing?

Unknown User•3y ago

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Tomasm21OP•3y ago

I provided you with all the necessary information to realize the problem. It only looks too large.

JavaBot•3y ago

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This post has been closed by <@312509109863710732>.

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What is an order in e-commerce application and how to control it. How is it related with user cart?

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