Short URL Management features:

• Generate unique short URLs for given long URLs.
• Allow users to define custom short codes (if not already in use).
• Track click statistics for each URL.
• URLs can have an optional expiration date.
• Support for active and expired URL statuses.

REST API:

• Fully-documented API using Springdoc OpenAPI.
• RESTful endpoints for creating, reading, updating, and deleting URLs.
• Pagination support for listing URLs.

Security:

• User authentication using JWT (JSON Web Tokens).
• Endpoints for user registration and login:
  • /api/v1/signup - Register a new user.
  • /api/v1/login - Authenticate a user and generate a JWT.
• Passwords are securely hashed using BCryptPasswordEncoder.
• Stateless, token-based session management.

REST API: CRUD endpoints for managing notes with operations like GET, POST, PUT, DELETE.

• Query-based searching to locate notes by a keyword.
• Data frequently reused within a request (e.g., fetched user details) is temporarily cached.

Security:

• Each user's notes are isolated and private.
• New users can sign up via /api/v1/signup.
• Endpoints /api/v1/signup and /api/v1/login are publicly accessible, while all other endpoints require authentication.
• Stateless architecture is implemented with JWT authentication for secure token-based sessions.
• Passwords are hashed using a secure PasswordEncoder implementation.
• Failed login attempts are tracked, with accounts locked temporarily after 3 unsuccessful login attempts.

Database:

• Managed with Spring Data JPA and PostgreSQL.
• Flyway handles schema migrations and initial data seeding.

Open API Documentation: Provides interactive Swagger UI for testing endpoints.

Web Application:

• Implements user-friendly navigation using the Thymeleaf template engine.
• Provides forms for login, signup, and note operations with dynamic content rendering.

Computation Strategies: Multiple approaches for calculating Fibonacci numbers, each optimised for different use cases:

• Recursive (O(2ⁿ)): Simple and educational, suitable for small inputs.
• Iterative (O(n), O(1) space): Efficient for medium-sized inputs.
• Dynamic Programming (O(n)): Uses bounded memoization for improved performance.
• Matrix Exponentiation: Supports both linear and logarithmic implementations, enabling efficient large-scale computations.

High-Precision Calculations:

• Supports BigInteger and BigDecimal for handling extremely large Fibonacci numbers.
• Configurable precision using MathContext for fine-grained control in calculations.

Performance Analysis:

• Execution time is logged for each computation strategy.
• Benchmarks implemented with JMH provide detailed insights, including:
  • Throughput (operations per millisecond)
  • Memory allocation rates
  • Garbage collection frequency and duration
• Results are exported (CSV/JSON) for further analysis.

Optimisation Insights:

• Identifies performance bottlenecks through collected metrics.
• Enables comparison of algorithm efficiency under different workloads.

Command-Line Interface:

• Interactive input for selecting computation strategy and Fibonacci index.
• Designed for experimentation and comparative analysis.

• Provides backend services to manage clients, planets, and tickets through HTTP.
• DAO layer is used to manage database transactions.
• DTO pattern is used for fetching and presenting a subset of entity attributes.
• The IGenericService interface and GenericService class define reusable CRUD methods that can handle any type of entity.
• TicketService uses Hibernate Query Language to execute custom queries for data fetching by joining multiple tables and selecting specific fields.
• Servlet is used to translate HTTP requests into service calls following the MVC design pattern.
• Thymeleaf templates to render responses.

• Returns pictures of the cute cats.
• Uses HttpFilter checking requests to /time endpoint to validate timezone parameter.
• Uses Thymeleaf to render response pages (for both success and error).
• You can deploy the application using Docker with the official Tomcat 10 image from Docker Hub.

• This is an exercise in web server implementation based on com.sun.net.httpserver.HttpServer.
• Before downloading images from http.cat API, the application sends a HEAD request to ensure the image exists at the source.
• For image handling optimization, caching is implemented at two levels:
  1. In-Memory Caching: To minimize file system access and API calls, recently requested images are stored as CachedImage objects, which include the image bytes and a timestamp.
  2. File System Caching: Before fetching an image from the remote API, the file system is checked for a locally stored copy to avoid repeated downloads.
• During the download, images are written to temporary files to avoid partial downloads in case of network errors.
• Added custom cat-like fonts as a cute extra feature.

• Used Flyway Gradle Plugin for DB migrations.
• Used Template Method Pattern to implement AbstractGenericService. The class works as a template and provides methods that represent steps for CRUD operations (preparing statements, executing queries, handling result sets) that vary by entity type, so they are implemented in subclasses.
• Created 2 mappers: EntityMapper - to map domain objects to SQL statements and vice versa, isolating SQL interactions from business logic, and JsonEntityMapper - to handle JSON data conversion, allowing the API to send and receive JSON-formatted data.
• MyHttpServer handles HTTP requests by checking the HTTP method (GET, POST, PUT, DELETE) and routing the request to the appropriate service method. Includes error handling for unsupported methods (405), missing resources (404), invalid requests (400).
• HttpServerFactory registers context paths (endpoints) for each service, enabling the API to expose different resources (e.g., /client, /worker). In this way, each service operates within a defined context path to provide clear routing based on resource type.

• Real-Time Currency Rates: Fetches and displays the latest exchange rates from multiple banks.
• User Settings:
  • Allows users to customise their settings, including preferred currencies and notification times.
  • Settings are loaded from storage during initialisation, allowing the bot to resume with the same settings as before a shutdown.
  • User settings can be stored in a JSON file and updated once the user clicks on a specific button. If the user doesn't choose any settings, default settings will be applied.
• Notifications:
  • Bot sends notifications to users based on their settings.
  • User can choose the convenient for them time for notifications.
• Scalability: Designed to be easily extendable for adding new banks or currencies, using external storage for user settings.