Pelaksanaan E-Dagang Mudah dengan Musim Semi

1. Gambaran Keseluruhan Aplikasi E-dagang Kami

Dalam tutorial ini, kami akan melaksanakan aplikasi e-commerce yang mudah. Kami akan mengembangkan API menggunakan Spring Boot dan aplikasi klien yang akan menggunakan API menggunakan Angular.

Pada dasarnya, pengguna akan dapat menambah / membuang produk dari senarai produk ke / dari troli membeli-belah dan membuat pesanan.

2. Bahagian Backend

Untuk mengembangkan API, kami akan menggunakan Spring Boot versi terbaru. Kami juga menggunakan pangkalan data JPA dan H2 untuk aspek kegigihan.

Untuk mengetahui lebih lanjut mengenai Spring Boot, anda boleh melihat siri artikel Spring Boot kami dan jika anda ingin membiasakan diri dengan membina REST API, sila lihat siri lain .

2.1. Ketergantungan Maven

Mari siapkan projek kami dan import kebergantungan yang diperlukan ke pom.xml kami .

Kami memerlukan beberapa pergantungan Spring Boot teras:

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

Kemudian, pangkalan data H2:

 com.h2database h2 1.4.197 runtime 

Dan akhirnya - perpustakaan Jackson:

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

Kami telah menggunakan Spring Initializr untuk cepat menyiapkan projek dengan pergantungan yang diperlukan.

2.2. Menyiapkan Pangkalan Data

Walaupun kami dapat menggunakan pangkalan data H2 dalam memori dengan Spring Boot, kami masih akan melakukan beberapa penyesuaian sebelum kami mulai mengembangkan API kami.

Kami akan mengaktifkan konsol H2 dalam fail application.properties kami sehingga kami benar-benar dapat memeriksa keadaan pangkalan data kami dan melihat apakah semuanya berjalan seperti yang kami harapkan .

Juga, berguna untuk memasukkan pertanyaan SQL ke konsol semasa mengembangkan:

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

Selepas menambah tetapan ini, kami akan dapat mengakses pangkalan data pada // localhost: 8080 / h2 konsol menggunakan JDBC: h2: mem: ecommercedb sebagai JDBC URL dan pengguna sa tanpa kata laluan.

2.3. Struktur Projek

Projek ini akan disusun dalam beberapa pakej standard, dengan aplikasi Angular dimasukkan ke dalam folder 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

Kita harus perhatikan bahawa semua antara muka dalam pakej repositori mudah dan memperluas CrudRepository Spring Data, jadi kami tidak akan memaparkannya di sini.

2.4. Pengendalian Pengecualian

Kami memerlukan pengendali pengecualian untuk API kami untuk menangani pengecualian akhirnya.

Anda boleh mendapatkan lebih banyak butiran mengenai topik tersebut dalam Ralat Pengendalian REST kami dengan Spring dan Custom Error Message Handling untuk artikel REST API .

Di sini, kami memberi tumpuan kepada ConstraintViolationException dan ResourceNotFoundException tersuai kami :

@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. Produk

Sekiranya anda memerlukan lebih banyak pengetahuan mengenai kegigihan di Spring, terdapat banyak artikel berguna dalam siri Spring Persistence .

Aplikasi kami akan menyokong hanya membaca produk dari pangkalan data , jadi kami perlu menambahkannya terlebih dahulu.

Mari buat kelas Produk mudah :

@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 }

Walaupun pengguna tidak berpeluang menambahkan produk melalui aplikasi, kami akan menyokong menyimpan produk dalam pangkalan data untuk mengisi senarai produk.

Perkhidmatan sederhana akan mencukupi untuk keperluan kami:

@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); } }

Pengawal sederhana akan menangani permintaan untuk mendapatkan senarai produk:

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

All we need now in order to expose the product list to the user – is to actually put some products in the database. Therefore, we'll make a use of CommandLineRunner class to make a Bean in our main application class.

This way, we'll insert products into the database during the application startup:

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

If we now start our application, we could retrieve product list via //localhost:8080/api/products. Also, if we go to //localhost:8080/h2-console and log in, we'll see that there is a table named PRODUCT with the products we've just added.

2.6. Orders

On the API side, we need to enable POST requests to save the orders that the end-user will make.

Let's first create the model:

@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

Dalam artikel ini, kami membuat aplikasi e-commerce sederhana. Kami membuat API di backend menggunakan Spring Boot dan kemudian kami menggunakannya di aplikasi frontend kami yang dibuat di Angular. Kami menunjukkan cara membuat komponen yang kami perlukan, membuatnya berkomunikasi antara satu sama lain dan mengambil / menghantar data dari / ke API.

Akhirnya, kami menunjukkan bagaimana menggabungkan kedua-dua aplikasi tersebut menjadi satu, aplikasi web yang dikemas dalam folder statik.

Seperti biasa, projek lengkap yang kami terangkan dalam artikel ini boleh didapati di projek GitHub.