Add the hexagonal module: Hexagonal Architecture (Ports and Adapters) in Spring Boot 4

2026-10-03 20:28:16 +00:00
parent ae681f85c4
commit fd6d0fa1e7
33 changed files with 1297 additions and 2 deletions
@@ -0,0 +1,39 @@
+package com.ankurm.hexagonal.app;
+
+import com.ankurm.hexagonal.WalletService;
+import com.ankurm.hexagonal.ports.WalletRepository;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.persistence.autoconfigure.EntityScan;
+import org.springframework.context.annotation.Bean;
+import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
+
+/**
+ * The composition root. Everything above this point in the article -- the domain, the ports,
+ * both adapters -- is wired together in exactly one place, and this is it.
+ * {@code WalletService} carries no {@code @Service} annotation, so without the {@code @Bean}
+ * method below, Spring would never construct it; the wiring is explicit, not discovered.
+ *
+ * <p>{@code scanBasePackages} covers {@code @Component}-style scanning, but Spring Data JPA's
+ * repository scan and JPA's entity scan each use their own default -- the package of this
+ * class, {@code com.ankurm.hexagonal.app} -- not {@code scanBasePackages}. That default is a
+ * sibling of {@code com.ankurm.hexagonal.persistence}, not an ancestor of it, so without the
+ * two annotations below Spring Data JPA silently finds zero repositories and the
+ * {@code JpaWalletRepositoryAdapter} bean fails to wire: see HexagonalApplicationTest's build
+ * log for the "No qualifying bean of type SpringDataWalletRepository" failure this caused.
+ */
+@SpringBootApplication(scanBasePackages = "com.ankurm.hexagonal")
+@EnableJpaRepositories(basePackages = "com.ankurm.hexagonal.persistence")
+@EntityScan(basePackages = "com.ankurm.hexagonal.persistence")
+public class HexagonalApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(HexagonalApplication.class, args);
+    }
+
+    @Bean
+    public WalletService walletService(WalletRepository walletRepository) {
+        return new WalletService(walletRepository);
+    }
+}
@@ -0,0 +1,3 @@
+spring.application.name=hexagonal
+spring.datasource.url=jdbc:h2:mem:hexagonaldb;DB_CLOSE_DELAY=-1
+spring.jpa.hibernate.ddl-auto=update
@@ -0,0 +1,80 @@
+package com.ankurm.hexagonal.app;
+
+import java.util.UUID;
+
+import com.ankurm.hexagonal.domain.Wallet;
+import com.ankurm.hexagonal.ports.WalletRepository;
+import com.ankurm.hexagonal.web.WalletController.BalanceResponse;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.resttestclient.TestRestTemplate;
+import org.springframework.boot.resttestclient.autoconfigure.AutoConfigureTestRestTemplate;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.test.context.DynamicPropertyRegistry;
+import org.springframework.test.context.DynamicPropertySource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * The whole stack, really wired, really running: a real embedded web server, a real H2
+ * database through the real persistence adapter, and HTTP requests that cross every
+ * boundary this article draws. If any of the wiring in {@link HexagonalApplication} were
+ * wrong, this is the test that would fail, not a unit test of any single class.
+ *
+ * <p>{@code @AutoConfigureTestRestTemplate} is required explicitly in Spring Boot 4 -- unlike
+ * Boot 3, a {@code @SpringBootTest(webEnvironment = RANDOM_PORT)} no longer auto-configures a
+ * {@code TestRestTemplate} bean on its own.
+ */
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@AutoConfigureTestRestTemplate
+class HexagonalApplicationTest {
+
+    @Autowired
+    TestRestTemplate rest;
+
+    @Autowired
+    WalletRepository walletRepository;
+
+    @DynamicPropertySource
+    static void datasource(DynamicPropertyRegistry registry) {
+        registry.add("spring.datasource.url",
+                () -> "jdbc:h2:mem:" + UUID.randomUUID() + ";DB_CLOSE_DELAY=-1");
+    }
+
+    @Test
+    void depositThenWithdrawOverHttpEndsAtTheRightBalanceThroughTheRealDatabase() {
+        walletRepository.save(new Wallet("w1", 1000));
+
+        ResponseEntity<BalanceResponse> afterDeposit = rest.postForEntity(
+                "/wallets/w1/deposit?amountCents=500", null, BalanceResponse.class);
+        System.out.println("After deposit: " + afterDeposit.getStatusCode() + " " + afterDeposit.getBody());
+
+        ResponseEntity<BalanceResponse> afterWithdraw = rest.postForEntity(
+                "/wallets/w1/withdraw?amountCents=200", null, BalanceResponse.class);
+        System.out.println("After withdraw: " + afterWithdraw.getStatusCode() + " " + afterWithdraw.getBody());
+
+        assertThat(afterDeposit.getBody().balanceCents()).isEqualTo(1500);
+        assertThat(afterWithdraw.getBody().balanceCents()).isEqualTo(1300);
+
+        // Reload straight from the real repository bean -- not from the HTTP response -- to
+        // prove the number actually landed in H2, not just in the controller's return value.
+        long persisted = walletRepository.findById("w1").orElseThrow().balanceCents();
+        System.out.println("Balance reloaded directly from WalletRepository: " + persisted);
+        assertThat(persisted).isEqualTo(1300);
+    }
+
+    @Test
+    void withdrawingTooMuchReturns409() {
+        walletRepository.save(new Wallet("w2", 100));
+
+        ResponseEntity<String> response = rest.postForEntity(
+                "/wallets/w2/withdraw?amountCents=101", null, String.class);
+        System.out.println("Overdraft attempt: " + response.getStatusCode());
+
+        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.CONFLICT);
+    }
+}