Una semplice implementazione dell'e-commerce con la primavera

1. Panoramica della nostra applicazione e-commerce

In questo tutorial implementeremo una semplice applicazione di e-commerce. Svilupperemo un'API utilizzando Spring Boot e un'applicazione client che utilizzerà l'API utilizzando Angular.

Fondamentalmente, l'utente sarà in grado di aggiungere / rimuovere prodotti da un elenco di prodotti a / da un carrello della spesa e di effettuare un ordine.

2. Parte backend

Per sviluppare l'API, utilizzeremo l'ultima versione di Spring Boot. Usiamo anche il database JPA e H2 per il lato della persistenza delle cose.

Per saperne di più su Spring Boot, puoi consultare la nostra serie di articoli Spring Boot e se desideri acquisire familiarità con la creazione di un'API REST, controlla un'altra serie .

2.1. Dipendenze di Maven

Prepariamo il nostro progetto e importiamo le dipendenze richieste nel nostro pom.xml .

Avremo bisogno di alcune dipendenze fondamentali di Spring Boot:

 org.springframework.boot spring-boot-starter-data-jpa 2.2.2.RELEASE   org.springframework.boot spring-boot-starter-web 2.2.2.RELEASE  

Quindi, il database H2:

 com.h2database h2 1.4.197 runtime 

E infine - la biblioteca di Jackson:

 com.fasterxml.jackson.datatype jackson-datatype-jsr310 2.9.6 

Abbiamo utilizzato Spring Initializr per impostare rapidamente il progetto con le dipendenze necessarie.

2.2. Configurazione del database

Anche se potremmo utilizzare il database H2 in memoria fuori dalla scatola con Spring Boot, faremo comunque alcune modifiche prima di iniziare a sviluppare la nostra API.

Ci permettiamo console H2 nel nostro application.properties di file in modo che possiamo effettivamente controllare lo stato della nostra banca dati e vedere se tutto sta andando come ci si aspetterebbe .

Inoltre, potrebbe essere utile registrare le query SQL nella console durante lo sviluppo:

spring.datasource.name=ecommercedb spring.jpa.show-sql=true #H2 settings spring.h2.console.enabled=true spring.h2.console.path=/h2-console

Dopo aver aggiunto queste impostazioni, saremo in grado di accedere al database su // localhost: 8080 / h2-console utilizzando jdbc: h2: mem: ecommercedb come URL JDBC e utente sa senza password.

2.3. La struttura del progetto

Il progetto sarà organizzato in diversi pacchetti standard, con l'applicazione Angular inserita nella cartella frontend:

├───pom.xml ├───src ├───main │ ├───frontend │ ├───java │ │ └───com │ │ └───baeldung │ │ └───ecommerce │ │ │ EcommerceApplication.java │ │ ├───controller │ │ ├───dto │ │ ├───exception │ │ ├───model │ │ ├───repository │ │ └───service │ │ │ └───resources │ │ application.properties │ ├───static │ └───templates └───test └───java └───com └───baeldung └───ecommerce EcommerceApplicationIntegrationTest.java

Dobbiamo notare che tutte le interfacce nel pacchetto del repository sono semplici ed estendono il CrudRepository di Spring Data, quindi ometteremo di visualizzarle qui.

2.4. La gestione delle eccezioni

Avremo bisogno di un gestore di eccezioni per la nostra API al fine di gestire correttamente eventuali eccezioni.

Puoi trovare maggiori dettagli sull'argomento nei nostri articoli sulla gestione degli errori per REST con Spring e sulla gestione dei messaggi di errore personalizzati per l'API REST .

Qui, ci concentriamo su ConstraintViolationException e sulla nostra ResourceNotFoundException personalizzata :

@RestControllerAdvice public class ApiExceptionHandler { @SuppressWarnings("rawtypes") @ExceptionHandler(ConstraintViolationException.class) public ResponseEntity handle(ConstraintViolationException e) { ErrorResponse errors = new ErrorResponse(); for (ConstraintViolation violation : e.getConstraintViolations()) { ErrorItem error = new ErrorItem(); error.setCode(violation.getMessageTemplate()); error.setMessage(violation.getMessage()); errors.addError(error); } return new ResponseEntity(errors, HttpStatus.BAD_REQUEST); } @SuppressWarnings("rawtypes") @ExceptionHandler(ResourceNotFoundException.class) public ResponseEntity handle(ResourceNotFoundException e) { ErrorItem error = new ErrorItem(); error.setMessage(e.getMessage()); return new ResponseEntity(error, HttpStatus.NOT_FOUND); } }

2.5. Prodotti

Se hai bisogno di maggiori conoscenze sulla persistenza in Spring, ci sono molti articoli utili nella serie Spring Persistence .

La nostra applicazione supporterà solo la lettura di prodotti dal database , quindi dobbiamo prima aggiungerne alcuni.

Creiamo una semplice classe Product :

@Entity public class Product { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @NotNull(message = "Product name is required.") @Basic(optional = false) private String name; private Double price; private String pictureUrl; // all arguments contructor // standard getters and setters }

Sebbene l'utente non abbia la possibilità di aggiungere prodotti tramite l'applicazione, supporteremo il salvataggio di un prodotto nel database per prepopolare l'elenco dei prodotti.

Un semplice servizio sarà sufficiente per le nostre esigenze:

@Service @Transactional public class ProductServiceImpl implements ProductService { // productRepository constructor injection @Override public Iterable getAllProducts() { return productRepository.findAll(); } @Override public Product getProduct(long id) { return productRepository .findById(id) .orElseThrow(() -> new ResourceNotFoundException("Product not found")); } @Override public Product save(Product product) { return productRepository.save(product); } }

Un semplice controller gestirà le richieste di recupero dell'elenco dei prodotti:

@RestController @RequestMapping("/api/products") public class ProductController { // productService constructor injection @GetMapping(value = { "", "/" }) public @NotNull Iterable getProducts() { return productService.getAllProducts(); } }

Tutto ciò di cui abbiamo bisogno ora per esporre l'elenco dei prodotti all'utente è di mettere effettivamente alcuni prodotti nel database. Pertanto, utilizzeremo la classe CommandLineRunner per creare un Bean nella nostra classe dell'applicazione principale.

In questo modo, inseriremo i prodotti nel database durante l'avvio dell'applicazione:

@Bean CommandLineRunner runner(ProductService productService) { return args -> { productService.save(...); // more products }

Se ora avviamo la nostra applicazione, potremmo recuperare l'elenco dei prodotti tramite // localhost: 8080 / api / products. Inoltre, se andiamo su // localhost: 8080 / h2-console e accediamo, vedremo che c'è una tabella denominata PRODUCT con i prodotti che abbiamo appena aggiunto.

2.6. Ordini

Sul lato API, dobbiamo abilitare le richieste POST per salvare gli ordini che l'utente finale effettuerà.

Creiamo prima il modello:

@Entity @Table(name = "orders") public class Order { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @JsonFormat(pattern = "dd/MM/yyyy") private LocalDate dateCreated; private String status; @JsonManagedReference @OneToMany(mappedBy = "pk.order") @Valid private List orderProducts = new ArrayList(); @Transient public Double getTotalOrderPrice() { double sum = 0D; List orderProducts = getOrderProducts(); for (OrderProduct op : orderProducts) { sum += op.getTotalPrice(); } return sum; } @Transient public int getNumberOfProducts() { return this.orderProducts.size(); } // standard getters and setters }

We should note a few things here. Certainly one of the most noteworthy things is to remember to change the default name of our table. Since we named the class Order, by default the table named ORDER should be created. But because that is a reserved SQL word, we added @Table(name = “orders”) to avoid conflicts.

Furthermore, we have two @Transient methods that will return a total amount for that order and the number of products in it. Both represent calculated data, so there is no need to store it in the database.

Finally, we have a @OneToMany relation representing the order's details. For that we need another entity class:

@Entity public class OrderProduct { @EmbeddedId @JsonIgnore private OrderProductPK pk; @Column(nullable = false) private Integer quantity; // default constructor public OrderProduct(Order order, Product product, Integer quantity) { pk = new OrderProductPK(); pk.setOrder(order); pk.setProduct(product); this.quantity = quantity; } @Transient public Product getProduct() { return this.pk.getProduct(); } @Transient public Double getTotalPrice() { return getProduct().getPrice() * getQuantity(); } // standard getters and setters // hashcode() and equals() methods }

We have a composite primary keyhere:

@Embeddable public class OrderProductPK implements Serializable { @JsonBackReference @ManyToOne(optional = false, fetch = FetchType.LAZY) @JoinColumn(name = "order_id") private Order order; @ManyToOne(optional = false, fetch = FetchType.LAZY) @JoinColumn(name = "product_id") private Product product; // standard getters and setters // hashcode() and equals() methods }

Those classes are nothing too complicated, but we should note that in OrderProduct class we put @JsonIgnore on the primary key. That's because we don't want to serialize Order part of the primary key since it'd be redundant.

We only need the Product to be displayed to the user, so that's why we have transient getProduct() method.

Next what we need is a simple service implementation:

@Service @Transactional public class OrderServiceImpl implements OrderService { // orderRepository constructor injection @Override public Iterable getAllOrders() { return this.orderRepository.findAll(); } @Override public Order create(Order order) { order.setDateCreated(LocalDate.now()); return this.orderRepository.save(order); } @Override public void update(Order order) { this.orderRepository.save(order); } }

And a controller mapped to /api/orders to handle Order requests.

Most important is the create() method:

@PostMapping public ResponseEntity create(@RequestBody OrderForm form) { List formDtos = form.getProductOrders(); validateProductsExistence(formDtos); // create order logic // populate order with products order.setOrderProducts(orderProducts); this.orderService.update(order); String uri = ServletUriComponentsBuilder .fromCurrentServletMapping() .path("/orders/{id}") .buildAndExpand(order.getId()) .toString(); HttpHeaders headers = new HttpHeaders(); headers.add("Location", uri); return new ResponseEntity(order, headers, HttpStatus.CREATED); }

First of all, we accept a list of products with their corresponding quantities. After that, we check if all products exist in the database and then create and save a new order. We're keeping a reference to the newly created object so we can add order details to it.

Finally, we create a “Location” header.

The detailed implementation is in the repository – the link to it is mentioned at the end of this article.

3. Frontend

Now that we have our Spring Boot application built up, it's time to move the Angular part of the project. To do so, we'll first have to install Node.js with NPM and, after that, an Angular CLI, a command line interface for Angular.

It's really easy to install both of those as we could see in the official documentation.

3.1. Setting Up the Angular Project

As we mentioned, we'll use Angular CLI to create our application. To keep things simple and have all in one place, we'll keep our Angular application inside the /src/main/frontend folder.

To create it, we need to open a terminal (or command prompt) in the /src/main folder and run:

ng new frontend

This will create all the files and folders we need for our Angular application. In the file pakage.json, we can check which versions of our dependencies are installed. This tutorial is based on Angular v6.0.3, but older versions should do the job, at least versions 4.3 and newer (HttpClient that we use here was introduced in Angular 4.3).

We should note that we'll run all our commands from the /frontend folder unless stated differently.

This setup is enough to start the Angular application by running ng serve command. By default, it runs on //localhost:4200 and if we now go there we'll see base Angular application loaded.

3.2. Adding Bootstrap

Before we proceed with creating our own components, let's first add Bootstrap to our project so we can make our pages look nice.

We need just a few things to achieve this. First, we need torun a command to install it:

npm install --save bootstrap

and then to say to Angular to actually use it. For this, we need to open a file src/main/frontend/angular.json and add node_modules/bootstrap/dist/css/bootstrap.min.css under “styles” property. And that's it.

3.3. Components and Models

Before we start creating the components for our application, let's first check out how our app will actually look like:

Now, we'll create a base component, named ecommerce:

ng g c ecommerce

This will create our component inside the /frontend/src/app folder. To load it at application startup, we'llinclude itinto the app.component.html:

Next, we'll create other components inside this base component:

ng g c /ecommerce/products ng g c /ecommerce/orders ng g c /ecommerce/shopping-cart

Certainly, we could've created all those folders and files manually if preferred, but in that case, we'd need to remember to register those components in our AppModule.

We'll also need some models to easily manipulate our data:

export class Product { id: number; name: string; price: number; pictureUrl: string; // all arguments constructor }
export class ProductOrder { product: Product; quantity: number; // all arguments constructor }
export class ProductOrders { productOrders: ProductOrder[] = []; }

The last model mentioned matches our OrderForm on the backend.

3.4. Base Component

At the top of our ecommerce component, we'll put a navbar with the Home link on the right:

 Baeldung Ecommerce 
    
  • Home (current)

We'll also load other components from here:

We should keep in mind that, in order to see the content from our components, since we are using the navbar class, we need to add some CSS to the app.component.css:

.container { padding-top: 65px; }

Let's check out the .ts file before we comment most important parts:

@Component({ selector: 'app-ecommerce', templateUrl: './ecommerce.component.html', styleUrls: ['./ecommerce.component.css'] }) export class EcommerceComponent implements OnInit { private collapsed = true; orderFinished = false; @ViewChild('productsC') productsC: ProductsComponent; @ViewChild('shoppingCartC') shoppingCartC: ShoppingCartComponent; @ViewChild('ordersC') ordersC: OrdersComponent; toggleCollapsed(): void { this.collapsed = !this.collapsed; } finishOrder(orderFinished: boolean) { this.orderFinished = orderFinished; } reset() { this.orderFinished = false; this.productsC.reset(); this.shoppingCartC.reset(); this.ordersC.paid = false; } }

As we can see, clicking on the Home link will reset child components. We need to access methods and a field inside child components from the parent, so that's why we are keeping references to the children and use those inside the reset() method.

3.5. The Service

In order for siblings components to communicate with each otherand to retrieve/send data from/to our API, we'll need to create a service:

@Injectable() export class EcommerceService { private productsUrl = "/api/products"; private ordersUrl = "/api/orders"; private productOrder: ProductOrder; private orders: ProductOrders = new ProductOrders(); private productOrderSubject = new Subject(); private ordersSubject = new Subject(); private totalSubject = new Subject(); private total: number; ProductOrderChanged = this.productOrderSubject.asObservable(); OrdersChanged = this.ordersSubject.asObservable(); TotalChanged = this.totalSubject.asObservable(); constructor(private http: HttpClient) { } getAllProducts() { return this.http.get(this.productsUrl); } saveOrder(order: ProductOrders) { return this.http.post(this.ordersUrl, order); } // getters and setters for shared fields }

Relatively simple things are in here, as we could notice. We're making a GET and a POST requests to communicate with the API. Also, we make data we need to share between components observable so we can subscribe to it later on.

Nevertheless, we need to point out one thing regarding the communication with the API. If we run the application now, we would receive 404 and retrieve no data. The reason for this is that, since we are using relative URLs, Angular by default will try to make a call to //localhost:4200/api/products and our backend application is running on localhost:8080.

We could hardcode the URLs to localhost:8080, of course, but that's not something we want to do. Instead, when working with different domains, we should create a file named proxy-conf.json in our /frontend folder:

{ "/api": { "target": "//localhost:8080", "secure": false } }

And then we need to open package.json and change scripts.start property to match:

"scripts": { ... "start": "ng serve --proxy-config proxy-conf.json", ... }

And now we just should keep in mind to start the application with npm start instead ng serve.

3.6. Products

In our ProductsComponent, we'll inject the service we made earlier and load the product list from the API and transform it into the list of ProductOrders since we want to append a quantity field to every product:

export class ProductsComponent implements OnInit { productOrders: ProductOrder[] = []; products: Product[] = []; selectedProductOrder: ProductOrder; private shoppingCartOrders: ProductOrders; sub: Subscription; productSelected: boolean = false; constructor(private ecommerceService: EcommerceService) {} ngOnInit() { this.productOrders = []; this.loadProducts(); this.loadOrders(); } loadProducts() { this.ecommerceService.getAllProducts() .subscribe( (products: any[]) => { this.products = products; this.products.forEach(product => { this.productOrders.push(new ProductOrder(product, 0)); }) }, (error) => console.log(error) ); } loadOrders() { this.sub = this.ecommerceService.OrdersChanged.subscribe(() => { this.shoppingCartOrders = this.ecommerceService.ProductOrders; }); } }

We also need an option to add the product to the shopping cart or to remove one from it:

addToCart(order: ProductOrder) { this.ecommerceService.SelectedProductOrder = order; this.selectedProductOrder = this.ecommerceService.SelectedProductOrder; this.productSelected = true; } removeFromCart(productOrder: ProductOrder) { let index = this.getProductIndex(productOrder.product); if (index > -1) { this.shoppingCartOrders.productOrders.splice( this.getProductIndex(productOrder.product), 1); } this.ecommerceService.ProductOrders = this.shoppingCartOrders; this.shoppingCartOrders = this.ecommerceService.ProductOrders; this.productSelected = false; }

Finally, we'll create a reset() method we mentioned in Section 3.4:

reset() { this.productOrders = []; this.loadProducts(); this.ecommerceService.ProductOrders.productOrders = []; this.loadOrders(); this.productSelected = false; }

We'll iterate through the product list in our HTML file and display it to the user:

{{order.product.name}}

${{order.product.price}}

3.8. Orders

We'll keep things as simple as we can and in the OrdersComponent simulate paying by setting the property to true and saving the order in the database. We can check that the orders are saved either via h2-console or by hitting //localhost:8080/api/orders.

We need the EcommerceService here as well in order to retrieve the product list from the shopping cart and the total amount for our order:

export class OrdersComponent implements OnInit { orders: ProductOrders; total: number; paid: boolean; sub: Subscription; constructor(private ecommerceService: EcommerceService) { this.orders = this.ecommerceService.ProductOrders; } ngOnInit() { this.paid = false; this.sub = this.ecommerceService.OrdersChanged.subscribe(() => { this.orders = this.ecommerceService.ProductOrders; }); this.loadTotal(); } pay() { this.paid = true; this.ecommerceService.saveOrder(this.orders).subscribe(); } }

And finally we need to display info to the user:

ORDER

  • {{ order.product.name }} - ${{ order.product.price }} x {{ order.quantity}} pcs.

Total amount: ${{ total }}

Pay Congratulation! You successfully made the order.

4. Merging Spring Boot and Angular Applications

We finished development of both our applications and it is probably easier to develop it separately as we did. But, in production, it would be much more convenient to have a single application so let's now merge those two.

What we want to do here is to build the Angular app which calls Webpack to bundle up all the assets and push them into the /resources/static directory of the Spring Boot app. That way, we can just run the Spring Boot application and test our application and pack all this and deploy as one app.

To make this possible, we need to open ‘package.json‘ again add some new scripts after scripts.build:

"postbuild": "npm run deploy", "predeploy": "rimraf ../resources/static/ && mkdirp ../resources/static", "deploy": "copyfiles -f dist/** ../resources/static",

We're using some packages that we don't have installed, so let's install them:

npm install --save-dev rimraf npm install --save-dev mkdirp npm install --save-dev copyfiles

The rimraf command is gonna look at the directory and make a new directory (cleaning it up actually), while copyfiles copies the files from the distribution folder (where Angular places everything) into our static folder.

Now we just need to run npm run build command and this should run all those commands and the ultimate output will be our packaged application in the static folder.

Then we run our Spring Boot application at the port 8080, access it there and use the Angular application.

5. Conclusion

In questo articolo abbiamo creato una semplice applicazione di e-commerce. Abbiamo creato un'API sul backend usando Spring Boot e poi l'abbiamo consumata nella nostra applicazione frontend realizzata in Angular. Abbiamo dimostrato come creare i componenti di cui abbiamo bisogno, farli comunicare tra loro e recuperare / inviare dati da / all'API.

Infine, abbiamo mostrato come unire entrambe le applicazioni in un'unica app Web in pacchetto all'interno della cartella statica.

Come sempre, il progetto completo che abbiamo descritto in questo articolo può essere trovato nel progetto GitHub.