Hexagonal architecture: a quick and practical example

hexagonal-architecture-poc/pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+   	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.0.5.RELEASE</version>
+		<relativePath />
+	</parent>
+	<groupId>com.baeldung</groupId>
+	<artifactId>hexagonal-architecture-poc</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>hexagonal-architecture-poc</name>
+	<description>Demo project for Hexagonal Architecture POC</description>
+
+	<properties>
+		<java.version>1.8</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+		<dependency>
+		    <groupId>com.h2database</groupId>
+		    <artifactId>h2</artifactId>
+		    <scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+</project>

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/HexagonalArchitecturePocApplication.java

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+package com.baeldung.hexagonal;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class HexagonalArchitecturePocApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(HexagonalArchitecturePocApplication.class, args);
+	}
+
+}

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/boundary/input/OrderService.java

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+package com.baeldung.hexagonal.boundary.input;
+
+import org.springframework.stereotype.Service;
+
+import com.baeldung.hexagonal.core.entities.Order;
+
+@Service public interface OrderService {
+	Iterable<Order> getOrders();
+	Order createOrder(Double total);
+	boolean registerOrder(Order order);
+}

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/boundary/output/OrderRepository.java

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+package com.baeldung.hexagonal.boundary.output;
+
+import java.util.List;
+
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.stereotype.Repository;
+
+import com.baeldung.hexagonal.core.entities.Order;
+
+@Repository public interface OrderRepository extends CrudRepository<Order, Long>{
+}

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/core/entities/Order.java

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+package com.baeldung.hexagonal.core.entities;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Table;
+
+@Entity @Table(name="Orders") public class Order {
+	@Id @GeneratedValue(strategy = GenerationType.IDENTITY) Long id;
+	Double total;
+	
+	public Order() {
+		super();
+	}
+	public Double getTotal() {
+		return total;
+	}
+	public void setTotal(Double total) {
+		this.total = total;
+	}
+	public Long getId() {
+		return id;
+	}
+	
+	
+}

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/core/services/OrderServiceImpl.java

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+package com.baeldung.hexagonal.core.services;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import com.baeldung.hexagonal.boundary.input.OrderService;
+import com.baeldung.hexagonal.boundary.output.OrderRepository;
+import com.baeldung.hexagonal.core.entities.Order;
+
+@Service public class OrderServiceImpl implements OrderService {
+
+	@Autowired OrderRepository orderRepository;
+	
+	@Override
+	public Iterable<Order> getOrders() {
+		return orderRepository.findAll();
+	}
+
+	@Override
+	public boolean registerOrder(Order order) {
+		if (order.getTotal() > 0)
+			orderRepository.save(order);
+		else
+			return false;
+		
+		return true;
+	}
+	
+	@Override
+	public Order createOrder(Double total) {
+		Order order = new Order();
+		order.setTotal(total);	
+		return order;
+	}
+}

hexagonal-architecture-poc/src/main/java/com/baeldung/hexagonal/outside/OrderController.java

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+package com.baeldung.hexagonal.outside;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import com.baeldung.hexagonal.boundary.input.OrderService;
+import com.baeldung.hexagonal.core.entities.Order;
+
+@RestController public class OrderController {
+
+	@Autowired OrderService orderService;
+	
+	@GetMapping(path = "/orders/list")
+	public Iterable<Order> getOrders(){
+		return orderService.getOrders();
+	}
+	
+	@GetMapping(path = "/orders/add")
+	public String placeOrder(@RequestParam Double total) {
+		boolean isPlaced = orderService.registerOrder(orderService.createOrder(total));	
+		return isPlaced ? "Ok" : "Nok";
+	}
+	
+	@GetMapping(path = "/orders/add-commission")
+	public String placeCommissionOrder(@RequestParam Double total) {
+		boolean isPlaced = orderService.registerOrder(orderService.createOrder(total*1.05));		
+		return isPlaced ? "Ok" : "Nok";
+	}
+
+}

hexagonal-architecture-poc/src/main/resources/application.properties

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+spring.datasource.url=jdbc:h2:mem:testdb
+spring.datasource.driverClassName=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=password
+spring.jpa.database-platform=org.hibernate.dialect.H2Dialect