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Objects and Their Relationships - Task Tracker

Overview

This document describes the domain objects, entities, DTOs (Data Transfer Objects), and their relationships within the Task Tracker application. The system follows a typical Spring Boot architecture with JPA entities, service layers, and RESTful APIs.

Core Domain Entities

1. User Entity

Location: com.example.tasktracker.entity.User

Purpose: Represents authenticated users in the system.

Attributes:

  • id: Long (Primary Key, Auto-generated)
  • username: String (Unique, Required, Max 50 chars)
  • password: String (Required, Encrypted)
  • email: String (Unique, Required)
  • enabled: Boolean (Default: true)
  • accountNonExpired: Boolean (Default: true)
  • accountNonLocked: Boolean (Default: true)
  • credentialsNonExpired: Boolean (Default: true)
  • role: String (Default: "USER", Max 20 chars)

Relationships:

  • One-to-One with Profile (User has one profile)
  • One-to-Many with Task (User owns multiple tasks)
  • One-to-Many with Tag (User owns multiple tags)

Security Features:

  • Implements Spring Security UserDetails interface requirements
  • Supports role-based access control
  • Account status tracking (enabled, locked, expired)

2. Task Entity

Location: com.example.tasktracker.entity.Task

Purpose: Represents individual tasks/todos in the system.

Attributes:

  • id: Long (Primary Key, Auto-generated)
  • title: String (Required, Non-blank)
  • description: String (Optional)
  • status: TaskStatus enum (Default: TODO)
  • createdAt: LocalDateTime (Auto-generated)
  • updatedAt: LocalDateTime (Auto-updated)

Relationships:

  • Many-to-One with User (Task belongs to one user)
  • Many-to-Many with Tag (Task can have multiple tags, tags can be on multiple tasks)

Business Rules:

  • Tasks are user-specific (multi-tenant by user)
  • Automatic timestamp management (creation/update)
  • Tag association through join table task_tags

3. Tag Entity

Location: com.example.tasktracker.entity.Tag

Purpose: Represents categorization labels for tasks.

Attributes:

  • id: Long (Primary Key, Auto-generated)
  • name: String (Required, 1-50 chars)
  • color: String (Hex color code, Default: "#3B82F6", Max 7 chars)
  • createdAt: LocalDateTime (Auto-generated)
  • updatedAt: LocalDateTime (Auto-updated)

Relationships:

  • Many-to-One with User (Tag belongs to one user)
  • Many-to-Many with Task (Tag can be applied to multiple tasks)

Constraints:

  • Unique constraint on (name, user_id) - users cannot have duplicate tag names
  • Color validation for hex color codes
  • User-scoped tags (multi-tenant by user)

4. Profile Entity

Location: com.example.tasktracker.entity.Profile

Purpose: Extended user information and preferences.

Attributes:

  • id: Long (Primary Key, Auto-generated)
  • firstName: String (Optional)
  • lastName: String (Optional)
  • email: String (Optional, may duplicate User.email for display)

Relationships:

  • One-to-One with User (Profile extends User information)

Usage:

  • Stores additional user information beyond authentication data
  • Allows for user profile management without affecting core auth data

5. TaskStatus Enum

Location: com.example.tasktracker.entity.TaskStatus

Purpose: Defines the possible states of a task.

Values:

  • TODO: Initial state for new tasks
  • IN_PROGRESS: Task is being worked on
  • DONE: Task has been completed

Usage:

  • Used in Task entity to track task progression
  • Supports typical Kanban-style workflow

Data Transfer Objects (DTOs)

Request DTOs

1. TaskRequest

Location: com.example.tasktracker.dto.TaskRequest

Purpose: Handles task creation and update requests.

Attributes:

  • title: String (Required, validated)
  • description: String (Optional)
  • status: TaskStatus (Default: TODO)
  • tagIds: List <Long> (List of tag IDs to associate)

2. TagRequest

Location: com.example.tasktracker.dto.TagRequest

Purpose: Handles tag creation and update requests.

3. ProfileRequest

Location: com.example.tasktracker.dto.ProfileRequest

Purpose: Handles profile update requests.

4. LoginRequest & RegisterRequest

Location: com.example.tasktracker.dto.LoginRequest, RegisterRequest

Purpose: Handle authentication requests.

Response DTOs

1. TaskResponse

Location: com.example.tasktracker.dto.TaskResponse

Purpose: Returns task data with associated tags.

Attributes:

  • id: Long
  • title: String
  • description: String
  • status: TaskStatus
  • createdAt: LocalDateTime
  • updatedAt: LocalDateTime
  • tags: List <TagResponse> (Associated tags)

2. TagResponse

Location: com.example.tasktracker.dto.TagResponse

Purpose: Returns tag data for client consumption.

3. ProfileResponse

Location: com.example.tasktracker.dto.ProfileResponse

Purpose: Returns user profile information.

4. AuthResponse

Location: com.example.tasktracker.dto.AuthResponse

Purpose: Returns authentication results and user session data.

Database Schema Relationships

Key Constraints

  1. Unique Constraints:

    • users.username (globally unique)
    • users.email (globally unique)
    • (tags.name, tags.user_id) (unique per user)

  2. Foreign Key Constraints:

    • profiles.user_id → users.id
    • tasks.user_id → users.id
    • tags.user_id → users.id
    • task_tags.task_id → tasks.id
    • task_tags.tag_id → tags.id

  3. Cascade Rules:

    • Tag associations: PERSIST, MERGE (no automatic deletion)
    • User deletion would cascade to tasks, tags, and profile

Object Lifecycle

Task Lifecycle

  1. Creation: User creates task → Status: TODO
  2. Progress: User updates task → Status: IN_PROGRESS
  3. Completion: User completes task → Status: DONE
  4. Tag Management: Users can add/remove tags at any stage
  5. Deletion: User can delete their own tasks

Tag Lifecycle

  1. Creation: User creates tag with name and color
  2. Association: Tags can be associated with multiple tasks
  3. Modification: User can update tag name and color
  4. Deletion: User can delete tags (removes associations)

User/Profile Lifecycle

  1. Registration: Creates User + empty Profile
  2. Authentication: Login/logout with session management
  3. Profile Updates: Modify profile information independently
  4. Account Management: Enable/disable, role changes

API Layer Mapping

Controllers → Services → Repositories

TaskController → TaskService → TaskRepository
TagController → TagService → TagRepository  
ProfileController → ProfileService → ProfileRepository
AuthController → AuthService → UserRepository

DTO Conversion

  • Request DTOs → Entities (in Service layer)
  • Entities → Response DTOs (in Service layer)
  • Validation applied at DTO level (Jakarta Validation)
  • Business Logic applied at Service level

Design Patterns Used

  1. Repository Pattern: Data access abstraction
  2. Service Layer Pattern: Business logic encapsulation
  3. DTO Pattern: Data transfer and API contracts
  4. Entity Pattern: Domain model representation
  5. MVC Pattern: Web layer organization
  6. Dependency Injection: Spring's IoC container