Add springdata JPA persistence example

.gitignore

@@ -1,7 +1,7 @@
 build/
 .gradle/
 .idea/
-
+.vscode/
 /.classpath
 /.project
 /bin/

build.gradle

@@ -14,6 +14,9 @@ repositories {
 dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-web'
     testImplementation('org.springframework.boot:spring-boot-starter-test')
+    implementation('org.springframework.boot:spring-boot-starter-data-jpa')
+    implementation('org.flywaydb:flyway-core')
+    runtimeOnly('com.h2database:h2')
 }
 
 test {

src/main/java/com/wilkins/showcase/controller/JsonUser.java

@@ -0,0 +1,11 @@
+package com.wilkins.showcase.controller;
+
+import com.wilkins.showcase.domain.User;
+
+import java.time.LocalDateTime;
+
+public record JsonUser(String externalId, String name, LocalDateTime createdAt) {
+    public static JsonUser from(User user) {
+        return new JsonUser(user.getExternalId(), user.getName(), user.getCreatedAt());
+    }
+}

src/main/java/com/wilkins/showcase/controller/UserController.java

@@ -0,0 +1,29 @@
+package com.wilkins.showcase.controller;
+
+import com.wilkins.showcase.service.UserService;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.Optional;
+
+@RestController
+@RequestMapping("/users")
+public class UserController {
+
+    private final UserService userService;
+
+    public UserController(UserService userService) {
+        this.userService = userService;
+    }
+
+    @PostMapping
+    ResponseEntity<JsonUser> createUser(@RequestBody String name) {
+        return Optional.of(userService.create(name))
+                .map(JsonUser::from)
+                .map(ResponseEntity::ok)
+                .orElseThrow();
+    }
+}

src/main/java/com/wilkins/showcase/domain/User.java

@@ -0,0 +1,85 @@
+package com.wilkins.showcase.domain;
+
+import jakarta.persistence.*;
+import org.hibernate.annotations.CreationTimestamp;
+
+import java.time.LocalDateTime;
+import java.util.Comparator;
+
+import static java.util.UUID.randomUUID;
+
+@Entity
+@Table(name = "users")
+public class User {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+    private String externalId;
+    private String name;
+    @CreationTimestamp
+    private LocalDateTime createdAt;
+
+    public User() {
+    }
+
+    public User(Long id, String externalId, String name, LocalDateTime createdAt) {
+        this.id = id;
+        this.externalId = externalId;
+        this.name = name;
+        this.createdAt = createdAt;
+    }
+
+    public static User with(String name) {
+        return new User(null, randomUUID().toString(), name, null);
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getExternalId() {
+        return externalId;
+    }
+
+    public void setExternalId(String externalId) {
+        this.externalId = externalId;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public LocalDateTime getCreatedAt() {
+        return createdAt;
+    }
+
+    public void setCreatedAt(LocalDateTime createdAt) {
+        this.createdAt = createdAt;
+    }
+
+    public static Comparator<User> userComparator() {
+        return (a, b) -> {
+            if (!a.getId().equals(b.getId())) {
+                return a.getId().compareTo(b.getId());
+            }
+            if (!a.getExternalId().equals(b.getExternalId())) {
+                return a.getExternalId().compareTo(b.getExternalId());
+            }
+            if (!a.getName().equals(b.getName())) {
+                return a.getName().compareTo(b.getName());
+            }
+            if (!a.getCreatedAt().isEqual(b.getCreatedAt())) {
+                return a.getCreatedAt().compareTo(b.getCreatedAt());
+            }
+            return 0;
+        };
+    }
+}

src/main/java/com/wilkins/showcase/service/DefaultUserService.java

@@ -0,0 +1,12 @@
+package com.wilkins.showcase.service;
+
+import com.wilkins.showcase.domain.User;
+import org.springframework.stereotype.Component;
+
+@Component
+public record DefaultUserService(UserRepository userRepository) implements UserService {
+    @Override
+    public User create(String name) {
+        return userRepository.save(User.with(name));
+    }
+}

src/main/java/com/wilkins/showcase/service/UserRepository.java

@@ -0,0 +1,9 @@
+package com.wilkins.showcase.service;
+
+import com.wilkins.showcase.domain.User;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface UserRepository extends CrudRepository<User, Long> {
+}

src/main/java/com/wilkins/showcase/service/UserService.java

@@ -0,0 +1,7 @@
+package com.wilkins.showcase.service;
+
+import com.wilkins.showcase.domain.User;
+
+public interface UserService {
+    User create(String name);
+}

src/main/resources/application.yml

@@ -0,0 +1,8 @@
+spring:
+  h2:
+    console:
+      enabled: true
+  datasource:
+    url: jdbc:h2:mem:showcase
+    username: showcase
+    password: Passw0rd!

src/main/resources/db/migration/V0__add_user_table.sql

@@ -0,0 +1,7 @@
+create table users
+(
+    id          bigint       not null auto_increment,
+    external_id varchar(120) not null,
+    name        varchar(120),
+    created_at  timestamp    not null default (current_timestamp)
+);

src/test/java/com/wilkins/showcase/service/DefaultUserServiceIntegrationTest.java

@@ -0,0 +1,39 @@
+package com.wilkins.showcase.service;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import java.time.LocalDateTime;
+
+import static com.wilkins.showcase.domain.User.userComparator;
+import static org.assertj.core.api.Assertions.assertThat;
+
+
+@SpringBootTest
+public class DefaultUserServiceIntegrationTest {
+
+    @Autowired
+    UserService underTest;
+    @Autowired
+    UserRepository userRepository;
+
+    @BeforeEach
+    void beforeEach() {
+        userRepository.deleteAll();
+    }
+
+    @Test
+    void canCreateUser() {
+        var bobFish = underTest.create("bob fish");
+
+        assertThat(bobFish.getCreatedAt()).isBeforeOrEqualTo(LocalDateTime.now());
+        assertThat(bobFish.getId()).isNotEqualTo(0);
+
+        assertThat(userRepository.findAll()).hasSize(1);
+        assertThat(userRepository.findById(bobFish.getId()))
+                .usingValueComparator(userComparator())
+                .hasValue(bobFish);
+    }
+}