Activity Tracker API

A small Spring Boot backend for tracking activities such as running, cycling, walking, jump rope, and strength training.

I built this project to practise and demonstrate clean first-version backend fundamentals while improving my Spring Boot skills. It focuses on a simple CRUD API, request/response DTOs, validation, layered application structure, JPA persistence, and controller testing.

Request Flow Diagram

Learning Goals

• Build a Spring Boot CRUD REST API.
• Use DTOs to separate incoming requests and outgoing responses from JPA entities.
• Validate request data with Bean Validation.
• Keep a clear controller, service, and repository structure.
• Persist activity data using Spring Data JPA with an H2 in-memory database.
• Test controller behaviour with MockMvc.

Tech Stack

• Java 21
• Spring Boot 4.0.6
• Spring Web MVC
• Spring Data JPA
• Bean Validation
• H2 database
• Maven Wrapper
• JUnit and MockMvc

Project Structure

activity-tracker/
├── pom.xml
├── mvnw
├── mvnw.cmd
├── src/
│   ├── main/
│   │   ├── java/com/andrew/activity_tracker/
│   │   │   ├── ActivityTrackerApplication.java
│   │   │   ├── controller/
│   │   │   │   └── ActivityController.java
│   │   │   ├── dto/
│   │   │   │   ├── ActivityRequest.java
│   │   │   │   └── ActivityResponse.java
│   │   │   ├── model/
│   │   │   │   ├── Activity.java
│   │   │   │   └── ActivityType.java
│   │   │   ├── repository/
│   │   │   │   └── ActivityRepository.java
│   │   │   └── service/
│   │   │       └── ActivityService.java
│   │   └── resources/
│   │       └── application.properties
│   └── test/
│       └── java/com/andrew/activity_tracker/
│           ├── ActivityTrackerApplicationTests.java
│           └── controller/
│               └── ActivityControllerTests.java

Running Tests

./mvnw clean test

Running Locally

./mvnw spring-boot:run

By default, the API runs on:

http://localhost:8080

API Endpoints

Method	Path	Purpose
POST	/api/activities	Create a new activity
GET	/api/activities	Get all activities
GET	/api/activities/{id}	Get one activity by ID
PUT	/api/activities/{id}	Update an existing activity
DELETE	/api/activities/{id}	Delete an activity

Supported Activity Types

• RUNNING
• CYCLING
• JUMP_ROPE
• WALKING
• STRENGTH

Example Create Request

{
	"activityType": "RUNNING",
	"activityDate": "2026-06-01",
	"durationMinutes": 30,
	"distanceMiles": 3.2,
	"notes": "Easy run"
}

Example Response

{
	"id": 1,
	"activityType": "RUNNING",
	"activityDate": "2026-06-01",
	"durationMinutes": 30,
	"distanceMiles": 3.2,
	"notes": "Easy run",
	"createdAt": "2026-06-01T10:15:30",
	"updatedAt": "2026-06-01T10:15:30"
}

Validation Rules

Field	Rule
activityType	Required. Must be one of the supported activity types.
activityDate	Required. Uses ISO date format, for example 2026-06-01.
durationMinutes	Required. Must be at least 1.
distanceMiles	Optional. Must be zero or positive if supplied.
notes	Optional. Maximum length is 500 characters.

Invalid requests return a 400 Bad Request response.

Test Coverage Summary

The project includes:

• A Spring Boot context-load smoke test.
• MockMvc controller tests for creating activities.
• MockMvc controller tests for listing activities.
• MockMvc controller tests for getting an activity by ID.
• MockMvc controller tests for updating activities.
• MockMvc controller tests for deleting activities.
• MockMvc coverage for selected validation and not-found cases.

What I Learned

This project helped me structure a small Spring Boot backend around clear responsibilities: controllers handle HTTP requests, DTOs define the API contract, validation protects incoming data, services contain application logic, and repositories manage persistence.

It also gave me practice using MockMvc to test REST endpoints without manually running the application.