Lernmaterialien

Grid

A simple Grid in Vaadin is the easiest way to show data as a table without any customization.

You just tell Vaadin:

• which class to display

• what data to show

And Vaadin does everything automatically.

Service

PizzaOrderService.java

    public ArrayList<PizzaOrder> findAll (){
        ArrayList<PizzaOrder> copy = new ArrayList<PizzaOrder>(orders);
        return copy;
    }

Return all pizza orders, but as a copy of the list.

Step-by-step explanation

ArrayList<PizzaOrder> copy = new ArrayList<PizzaOrder>(orders);

• creates a new ArrayList

• copies all elements from orders into it

return copy;

• returns the new list instead of the original one

Why not return orders directly?

return orders;

then outside code could do:

service.findAll().clear();

❌ This would delete your internal data!

Why this version is better

return new ArrayList<>(orders);

✅ protects your internal list
✅ prevents external modification of the original list

Important detail

This is a shallow copy:

• the list is new ✅

• but the objects inside are the same ❗

So:

PizzaOrder p = service.findAll().get(0);
p.setSize("XL");

👉 still changes the original object

Simplest possible Grid

public class OrdersView extends VerticalLayout {
    private final Grid<PizzaOrder> grid = new Grid<>(PizzaOrder.class, true);
    private final PizzaOrderService pizzaOrderService;

    public OrdersView(@Autowired PizzaOrderService pizzaOrderService) {
        this.pizzaOrderService = pizzaOrderService;
        setSpacing(true);

        setSizeFull();
        grid.setSizeFull();
        add(grid);
        reload();
    }

    private void reload() {
        grid.setItems(pizzaOrderService.findAll());
    }
}

Let’s go through your code step by step in a simple way 👇

Class definition

public class OrdersView extends VerticalLayout {

👉 OrdersView is a UI class (View) in Vaadin
👉 It extends VerticalLayout → components are arranged from top to bottom

Grid field

private final Grid<PizzaOrder> grid = new Grid<>(PizzaOrder.class, true);

👉 Creates a table (Grid) to display PizzaOrder objects

• PizzaOrder.class → tells Vaadin what data type to show

• true → automatically shows all fields as columns

✔ No need to define columns manually

Service field

private final PizzaOrderService pizzaOrderService;

👉 This is your service (business logic layer)
👉 It provides the data (list of orders)

Constructor (important part)

public OrdersView(@Autowired PizzaOrderService pizzaOrderService) {

👉 Spring gives you the PizzaOrderService automatically

Equivalent idea:

new OrdersView(new PizzaOrderService());

Inside the constructor:

this.pizzaOrderService = pizzaOrderService;

👉 Saves the service in the class so you can use it later

Spacing

setSpacing(true);

👉 Adds spacing between UI elements

Full screen size

setSizeFull();
grid.setSizeFull();

👉 Makes the layout and grid use full screen size

add

add(grid);

👉 Adds the grid to the UI
👉 Now it becomes visible

reload

reload();

👉 Loads data into the grid

reload() method

private void reload() {
    grid.setItems(pizzaOrderService.findAll());
}

👉 This is the key logic:

1. Calls the service:

   pizzaOrderService.findAll()

   → returns all orders

2. Sets data into the grid:

   grid.setItems(...)

   → grid displays the data

What happens when the view opens?

Step-by-step:

1. Vaadin creates OrdersView

2. Spring injects PizzaOrderService

3. Constructor runs

4. Grid is added to layout

5. reload() is called

6. Data is loaded into the grid

7. User sees a table with pizza orders

Domain

Add a no-argument constructor for JPA

Because of @Entity, JPA requires a constructor without arguments.

Current constructor:

    public PizzaOrder() throws PizzaOrderException {
        setOrderId();
        setOrderDate(LocalDate.now());
        setPizza("Margherita");
        setSize("Large");
        setPrice(14.0);
        setQuantity(1);
        setGarlic(true);
    }

is not good for JPA, because JPA expects a simple no-arg constructor.

Use:

public PizzaOrder() {
}

OR

@NoArgsConstructor

If you want default values, it is better to set them elsewhere, not in the JPA default constructor.

GIT!!!