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CRUD 101 — Java + Spring Boot Onboarding Task

Assignee: @team Sprint: Backlog (onboarding) Estimated effort: 4–6h Generated: 2026-03-02 Last updated: 2026-03-02

Task · INFRA · EP-011

Title: [TASK][INFRA] CRUD 101 — Spring Boot + MongoDB + REST API warm-up Labels: task onboarding backend java spring Type: ⚙️ Configuration / Setup Sprint: Backlog (no sprint) Estimate: 4–6h

Objective

Build a minimal but complete CRUD REST API using Java 17 + Spring Boot 3.2.2 + MongoDB. This task has no business logic — it exists purely as a warm-up exercise so the team can validate the local dev setup, get comfortable with the Spring Boot project structure, and practice writing basic unit/integration tests before working on real features.

Stack: Java 17 · Spring Boot 3.2.2 · Spring Data MongoDB · JUnit 5 · Mockito · Flapdoodle Embedded MongoDB (tests)

Context

You will build a simple Book resource with full CRUD backed by MongoDB (already configured in this repo) and a few automated tests. At the end you should be able to:

  • Run the app locally and hit all endpoints via Postman or curl
  • See documents persisted in MongoDB (ecolink_db)
  • Have at least one passing unit test and one passing integration test

Subtasks

1 — Project Setup

  • Project already exists at ecolink-api-java — skip generation from start.spring.io
  • Imported into VS Code
  • pom.xml already contains: spring-boot-starter-web, spring-boot-starter-data-mongodb, spring-boot-starter-validation, lombok, spring-boot-starter-test
  • application.properties already configured for MongoDB: 
    spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=ecolink_db
  • Add the Flapdoodle Embedded MongoDB dependency to pom.xml for integration tests: 
    <dependency>
  <groupId>de.flapdoodle.embed</groupId>
  <artifactId>de.flapdoodle.embed.mongo.spring3x</artifactId>
  <version>4.13.1</version>
  <scope>test</scope>
</dependency>
  • Make sure MongoDB is running locally: mongod --dbpath /your/data/path
  • Confirm the app starts without errors: ./mvnw spring-boot:run

2 — Document (Model)

  • Create Book.java in the model/ package (package exists but is empty — only a .gitkeep file):
    • id (String, auto-generated by MongoDB)
    • title (String, not null, max 200 chars)
    • author (String, not null)
    • publishedYear (Integer)
    • isbn (String, unique)
  • Annotate with @Document(collection = "books"), @Id, @Field, @NotBlank
  • Use Lombok: @Data, @NoArgsConstructor, @AllArgsConstructor, @Builder

3 — Repository

  • Create BookRepository.java in the repository/ package (package exists but is empty — only a .gitkeep file)
  • Extend MongoRepository<Book, String>
  • Add one custom query method: List<Book> findByAuthorIgnoreCase(String author)

4 — Service

  • Create BookService.java in the service/ package (package exists but is empty — only a .gitkeep file)
  • Implement methods: findAll(), findById(String id), findByAuthor(String author), create(Book book), update(String id, Book book), delete(String id)
  • Throw ResponseStatusException(HttpStatus.NOT_FOUND) when a book is not found by ID

5 — Controller

  • Create BookController.java in the controller/ package (package exists but is empty — only a .gitkeep file) with @RestController and @RequestMapping("/api/books")

  • Implement endpoints:

    Method Path Description Success status
    GET /api/books List all books 200
    GET /api/books/{id} Get book by ID 200
    GET /api/books?author={name} Filter by author 200
    POST /api/books Create book 201
    PUT /api/books/{id} Full update 200
    DELETE /api/books/{id} Delete book 204

  • Use @Valid on @RequestBody to trigger Bean Validation

  • Return a meaningful 404 response when a book is not found

6 — Unit Tests

  • Create BookServiceTest.java in src/test/ (test directory exists but has no test files)
  • Use @ExtendWith(MockitoExtension.class) and @Mock BookRepository
  • Write at least 3 test cases:
    • findById_existingId_returnsBook()
    • findById_notFound_throwsException()
    • delete_existingId_callsRepository()

7 — API / Integration Tests

  • Create BookControllerTest.java using @SpringBootTest + @AutoConfigureMockMvc (no test files exist yet)
  • Tests will run against Flapdoodle Embedded MongoDB (added in step 1 — no extra config file needed)
  • Create src/test/resources/application-test.properties to isolate the test database: 
    spring.data.mongodb.database=ecolink_test_db
  • Annotate the test class with @ActiveProfiles("test")
  • Write at least 3 integration test cases using MockMvc:
    • POST /api/books with valid payload → 201 + body contains id
    • GET /api/books/{id} for existing book → 200 + correct fields
    • GET /api/books/{id} for non-existing ID → 404

8 — Manual API Test via MongoDB

  • With the app running against the local MongoDB instance, use Postman or curl to:
    • Create 3 books via POST /api/books
    • Retrieve the list via GET /api/books
    • Update one book via PUT /api/books/{id}
    • Delete one book via DELETE /api/books/{id}
  • Open MongoDB Compass or mongosh and confirm the books collection in ecolink_db reflects the operations

Sample Payloads

POST /api/books

{
  "title": "Clean Code",
  "author": "Robert C. Martin",
  "publishedYear": 2008,
  "isbn": "978-0132350884"
}

Expected 201 response

{
  "id": "6630f1a2b3c4d5e6f7a8b9c0",
  "title": "Clean Code",
  "author": "Robert C. Martin",
  "publishedYear": 2008,
  "isbn": "978-0132350884"
}

GET /api/books/000000000000000000000099 (not found)

{
  "status": 404,
  "error": "Not Found",
  "message": "Book with id 000000000000000000000099 not found"
}

Definition of Done

  • Flapdoodle Embedded MongoDB dependency added to pom.xml
  • App starts cleanly against local MongoDB with no errors
  • All 6 REST endpoints respond correctly (manually verified via Postman/curl)
  • Documents visible in MongoDB (ecolink_db.books) after POST/PUT/DELETE operations
  • All unit tests pass: ./mvnw test
  • All integration tests pass using Embedded MongoDB
  • No compiler warnings related to unchecked types or deprecated APIs
  • Code pushed to a feature branch and PR opened for review

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