MicroSpringBoot - IoC Framework for Java Web Applications

Project Description

This project implements a custom HTTP web server in Java (without using Spring) with Inversion of Control (IoC) capabilities similar to Spring Boot. The current version focuses on three major goals:

• Concurrent HTTP request handling
• Graceful server shutdown
• Containerized deployment with Docker (local and AWS EC2)

The framework also keeps support for:

• Building web applications from POJOs (Plain Old Java Objects)
• Automatically scanning components with annotations
• Supporting custom annotations: @RestController, @GetMapping, @RequestParam

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Framework Architecture

Main Components

1. HttpServer: HTTP server listening on port 8080

   • Handles HTTP GET requests
   • Routes requests to corresponding controllers
   • Serves static files from /webroot
   • Uses a thread pool to process requests concurrently
   • Registers a JVM shutdown hook for graceful termination

2. ComponentScanner: Automatic classpath scanning

   • Searches for classes annotated with @RestController
   • Registers methods with @GetMapping
   • Processes parameters with @RequestParam

3. Custom Annotations:

   • @RestController: Marks classes as web controllers
   • @GetMapping(path): Maps methods to HTTP routes
   • @RequestParam(value, defaultValue): Injects query parameters

4. WebFramework: Main entry point

   • Initializes ComponentScanner
   • Configures static files
   • Starts the HTTP server

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Implemented Features

1. Concurrent Request Handling

The server now handles multiple client requests at the same time by delegating each accepted socket to an ExecutorService thread pool.

This avoids the old sequential behavior where one slow request could block the next incoming requests.

2. Graceful Shutdown

The framework now supports graceful shutdown using a JVM shutdown hook:

• Stops the accept loop
• Closes the server socket
• Stops receiving new tasks in the thread pool
• Waits for in-flight requests to finish
• Forces shutdown only if timeout is exceeded

This behavior is triggered on controlled JVM termination events (for example, Ctrl + C or System.exit()).

3. Docker Local Workflow

Step 1: Create Dockerfile

Step 2: Build image

docker build --tag microspringbootimage .

Step 3: Run container

docker run -d -p 34000:8080 --name primercontenedordemicrospringboot microspringbootimage

Step 4: Validate locally

Open:

http://localhost:34000/

4. Docker Hub Publication

Step 1: Create Docker Hub repository

Step 2: Tag local image

docker tag microspringbootimage <dockerhub-user>/microspringboot:latest

Step 3: Push image

docker push <dockerhub-user>/microspringboot:latest

5. AWS EC2 Deployment with Docker

Step 1: Connect to EC2 instance

ssh -i your-key.pem ec2-user@your-instance-ip

Step 2: Install Docker in EC2

Step 3: Pull image and run container

docker pull <dockerhub-user>/microspringboot:latest
docker run -d -p 42000:8080 --name microspringboot-aws <dockerhub-user>/microspringboot:latest

Step 4: Open EC2 inbound port

Allow inbound traffic on port 42000 in the Security Group.

Step 5: Validate from browser

Open:

http://your-ec2-public-ip:42000/

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Local Installation and Execution

Prerequisites

• Java 17 or higher
• Maven 3+
• Git

Step 1: Clone the Repository

git clone https://github.com/DASarria/Concurrent-MicroSpringBoot.git
cd Concurrent-MicroSpringBoot

Step 2: Compile the Project

mvn clean compile

Step 3: Run the Server

java -cp target/classes edu.co.escuelaing.arep.WebFramework

Step 4: Access the Application

Open your browser and visit:

http://localhost:8080/

Available Endpoints

Route	Description
/	Welcome page
/pi	Returns the value of PI
/euler	Returns Euler's number
/hello	Simple greeting
/greeting	Greeting with optional parameter ?name=YourName
/newController	Dynamic controller example

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Project Structure

Concurrent-MicroSpringBoot/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── edu/co/escuelaing/arep/
│   │   │       ├── WebFramework.java                 # Entry point
│   │   │       ├── ComponentScanner.java             # Automatic scanning
│   │   │       ├── MicroSpringBoot.java              # Reflection-based launcher
│   │   │       ├── HTTPComponents/
│   │   │       │   ├── HttpServer.java               # Concurrent HTTP server + graceful shutdown
│   │   │       │   ├── HttpRequest.java              # Request wrapper
│   │   │       │   ├── HttpResponse.java             # Response wrapper
│   │   │       │   └── WebMethod.java                # Functional interface
│   │   │       ├── annotations/
│   │   │       │   ├── RestController.java           # Class annotation
│   │   │       │   ├── GetMapping.java               # Method annotation
│   │   │       │   └── RequestParam.java             # Parameter annotation
│   │   │       └── controllers/
│   │   │           ├── HelloController.java          # Example controller
│   │   │           ├── GreetingController.java       # Controller with params
│   │   │           └── NewController.java            # Additional controller example
│   │   └── resources/
│   │       └── webroot/
│   │           └── index.html                        # Static page
│   └── test/
│       └── java/
│           └── edu/co/escuelaing/arep/
│               └── AppTest.java
├── assets/                                           # README images
├── Dockerfile                                        # Container image definition
├── pom.xml                                           # Maven configuration
└── README.md

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Technical Features

Inversion of Control (IoC)

The framework implements IoC through:

• Automatic classpath scanning:

  • Recursively searches all classes in edu.co.escuelaing.arep
  • Filters only classes with @RestController

• Dependency injection:

  • Uses reflection to extract methods with @GetMapping
  • Processes parameters with @RequestParam
  • Injects values from HTTP query parameters

Concurrency and Graceful Termination

• Fixed-size thread pool for request concurrency
• Controlled shutdown flow through JVM shutdown hook
• Proper release of socket and executor resources

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Author

David Sarria - March 2026