messages-queue

A simple Java-based message queue implementation with file storage.

Features

• Thread-safe message queue using BlockingQueue
• Unique message IDs - automatically generated UUIDs for each message
• File-based storage - messages survive application restarts
• Producer/Consumer pattern - separate classes for producing and consuming messages

Classes

Message

Represents a message with:

• Unique ID (UUID)
• String payload
• Two constructors:
  • Message(String payload) - creates new message with generated ID
  • Message(String id, String payload) - loads existing message with preserved ID

MessageQueue

The main messages queue implementation with:

• enqueue(Message message) - adds message to queue and saves to file
• dequeue() - removes and returns message from queue
• size() - returns current queue size
• Automatic file loading on startup
• Saves messages to a specified file

Producer

Handles message production with:

• produce(String payload) - creates and enqueues a new message
• Wraps the message creation and enqueuing process

Consumer

Handles message consumption with:

• poll() - retrieves and returns the next message from the queue
• Wraps the message dequeuing process

App

Demo application showing producer/consumer usage pattern

Usage

// Create a message queue with file storage
MessageQueue queue = new MessageQueue("messages.log");

// Create producer and consumer
Producer producer = new Producer(queue);
Consumer consumer = new Consumer(queue);

// Produce messages
producer.produce("Hello, World!");
producer.produce("Second message");

// Consume messages
Message delivered = consumer.poll();
System.out.println("Delivered: " + delivered);

// Check queue size
int size = queue.size();

Building and Running

This is a Maven project. To build and run:

# Compile
mvn compile

# Run the demo
mvn exec:java -Dexec.mainClass="com.ofek.queue.App"

# Run tests
mvn test

File Format

Messages are stored in pipe-delimited format:

UUID|payload
another-uuid|another message

Requirements

• Java 21
• Maven 3.x