Simple Java HTTP Server

This project implements a minimal, educational HTTP server in Java.
The goal is to understand low-level request handling, routing, controllers, and response building without relying on large frameworks.

It includes:

• Socket-based HTTP server
• Basic router and mapping system
• Controllers implementing a RequestHandler interface
• Request parsing (method, path, headers, body)
• Response builder with support for multiple formats
• A complete class diagram for architecture visibility

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🚀 Overview

The server listens on a configurable port and processes each incoming socket by:

1. Parsing the HTTP request into a Request object
2. Passing it to the Router
3. Resolving the appropriate RequestHandler via Routes
4. Building the HTTP response with Response helpers
5. Sending the result back through the socket

The structure is intentionally simple so you can extend it — adding controllers, middleware, or even template rendering.

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📦 Project Structure

java-echo-server/
├── README.md
├── src
│   └── main
│       └── java
│           └── com
│               └── server
│                   ├── controller
│                   │   ├── EchoController.java
│                   │   ├── GreetingController.java
│                   │   ├── NotFoundController.java
│                   │   └── RequestHandler.java
│                   ├── http
│                   │   ├── HttpMethod.java
│                   │   ├── HttpServer.java
│                   │   ├── Request.java
│                   │   └── Response.java
│                   ├── Main.java
│                   ├── router
│                   │   ├── Router.java
│                   │   └── Routes.java
│                   └── utils
│                       └── ResponseTemplate.java
└── tests
    ├── load_get_greeting.sh
    ├── load_post_message.sh
    └── run_all_load_tests.sh

🧩 Class Diagram

Below is a full Mermaid UML diagram representing the architecture:

sequenceDiagram
    autonumber

    participant Client
    participant HttpServer
    participant Router
    participant Routes
    participant Controller
    participant Response

    Client ->> HttpServer: HTTP request
    HttpServer ->> Router: handle(socket)
    Router ->> Routes: getOrNotFound(request)
    Routes -->> Router: handler
    Router ->> Controller: handle(request)
    Controller -->> Router: body
    Router ->> Response: build response
    Response -->> Router: http string
    Router -->> Client: http response

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🧱Architecture Overview

flowchart LR

    Client["Client(curl / browser)"]

    subgraph Server["Java Echo Server"]
        HttpServer["HttpServer(Socket listener)"]
        Router["Router(Request dispatcher)"]
        Routes["Routes(Path → Handler mapping)"]

        subgraph Controllers
            Greeting["GreetingController"]
            Echo["EchoController"]
            NotFound["NotFoundController"]
        end

        subgraph HTTP
            Request["Request(Parsed HTTP)"]
            Response["Response(HTTP builder)"]
            Templates["ResponseTemplate"]
        end
    end

    Client --> HttpServer
    HttpServer --> Router
    Router --> Request
    Router --> Routes
    Routes --> Greeting
    Routes --> Echo
    Routes --> NotFound
    Router --> Response
    Response --> Templates
    Response --> Client

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