Event-Driven Log Processing System (Java)

Project Overview

This project implements an event-driven log processing system in Java.It parses structured application logs, converts each log entry into an immutable event, and processes those events through a flexible listener-based architecture.

The goal of this project is to demonstrate:

• Strong object-oriented design

• Event-based architecture

• Proper use of interfaces

• Application of common design patterns

This project follows a generator–event–listener model and is designed to be easily extensible.

Key Concepts & Objectives

• Event-driven programming

• Interface-based design

• Observer (Listener) pattern

• Factory Method pattern

• Singleton pattern

• Immutable domain objects

• File I/O and log parsing

• Clean and maintainable project structure

Architecture Summary

The system is organized into three main roles:

Events

• Represent immutable log entries

• Extend java.util.EventObject

• Expose log data through read-only getters

Generator

• Responsible for creating LogEvent instances

• Maintains a list of subscribed listeners

• Notifies listeners whenever a new event is created

• Implemented as a Singleton

• Acts as a Factory for events

Listeners

• Subscribe to the generator

• React to events independently

• Can filter events or aggregate statistics

• Do not modify events

Processing Flow

1. LogParser reads the application.log file line by line

2. Each line is parsed into typed fields

3. LogGenerator creates a LogEvent

4. The generator notifies all registered listeners

5. Each listener independently reacts to the event

How to Run

1. Clone the repository

2. Open the project in IntelliJ IDEA

3. Ensure application.log is present

4. Run Main.java

5. Check the output/ directory for generated files

Possible Improvements

• Add unit tests (JUnit)

• Support JSON or CSV output formats

• Externalize configuration using a properties file

• Allow listeners to subscribe to multiple filters

• Improve error handling in log parsing