Hotaru Web Framework

Small, sweet, easy framework for full-stack Rust web applications

Former Codebase

We rebased our code since July this year. Please refer to the following link if you are interested in our history of building the framework

https://github.com/Redstone-D/starberry

📋 Overview

Hotaru is a lightweight, intuitive web framework focused on simplicity and productivity. It supports regex-based routing, tree-structured URLs, and integrates seamlessly with the Akari templating system.

Example Project

MSRV: 1.86

✨ Key Features

Simple API: Intuitive request/response handling with minimal boilerplate
Full-Stack: Built-in template rendering with Akari templates
Flexible Routing: Support for regex patterns, literal URLs, and nested routes
Asynchronous: Built with Tokio for efficient async handling
Form Handling: Easy processing of form data and file uploads
Middleware Support: Create reusable request processing chains
Multi-Protocol Support: Handle HTTP/HTTPS, WebSocket, and custom TCP protocols
Security: Built-in request validation, size limits, and safety controls
Client Information: Access client IP addresses and connection details directly from handlers

🚀 Quick Start

use hotaru::prelude::*;

pub static APP: SApp = Lazy::new(|| {
    App::new()
        .binding("127.0.0.1:3000")
        .build()
});

#[tokio::main]
async fn main() {
    APP.clone().run().await;
}

endpoint! {
    APP.url("/"),
    pub index<HTTP> {
        text_response("Hello, Hotaru!")
    }
}

📦 Installation

Using the CLI Tool (Recommended)

Install the Hotaru CLI tool:

cargo install hotaru

Create a new project:

hotaru new my_app

cd my_app

cargo run

Manual Installation

Add to your Cargo.toml:

[dependencies]

hotaru = "0.7.3"

tokio = { version = "1", features = ["full"] }

Optional Features

Hotaru supports the following optional features:

debug: Enable debug logging for development and troubleshooting
external-ctor: Use the external ctor crate instead of Hotaru's built-in constructor implementation

Note: When enabling external-ctor, you must also add ctor to your dependencies:
```
[dependencies]

hotaru = { version = "0.7.3", features = ["external-ctor"] }

ctor = "0.4.0"  # Required when external-ctor feature is enabled

tokio = { version = "1", features = ["full"] }
```
By default, Hotaru uses a built-in constructor implementation that doesn't require any external dependencies.

🛠️ Binary Commands

Hotaru provides a CLI tool to help you scaffold and manage projects quickly.

⚠️ IMPORTANT: It is crucial to use the CLI tool (hotaru new or hotaru init) when creating a new Hotaru project. The CLI automatically generates essential files including:

build.rs - Required for asset management and resource copying
resource.rs - Helper module for locating templates and static files at runtime

Without these files, your project will not be able to properly locate and serve templates or static assets. Manual setup is significantly more complex and error-prone.

Installation

cargo install hotaru

Note: After installation, make sure Cargo's bin directory is in your PATH. If the hotaru command is not found, add Cargo's bin directory to your PATH:

# Linux/macOS

export PATH="$HOME/.cargo/bin:$PATH"


# Windows (PowerShell)

$env:Path += ";$env:USERPROFILE\.cargo\bin"

To make this permanent, add the export line to your shell configuration file (~/.bashrc, ~/.zshrc, etc.).

Available Commands

`hotaru new <project_name>`

Create a new Hotaru project with a complete project structure:

hotaru new my_app

This generates:

src/main.rs - Main application entry point with a hello world endpoint
src/resource.rs - Resource file locator helper module
build.rs - Build script for asset management
Cargo.toml - Pre-configured with Hotaru dependencies
templates/ - Directory for Akari HTML templates
programfiles/ - Directory for static assets (CSS, JS, images)

The generated project uses the latest Hotaru features including:

LApp! macro for clean app initialization
endpoint! macro for routing
Proper resource management with build-time asset copying

`hotaru init`

Initialize an existing Cargo project with Hotaru scaffolding:

cd my_existing_project

hotaru init

This command adds the same structure as hotaru new but to your current project directory.

Running Your Project

After creating a project:

cd my_app

cargo run

Your server will start at http://127.0.0.1:3000 by default, serving a "Hello, world!" response at the root path.

Project Structure

my_app/
├── Cargo.toml              # Dependencies and project metadata
├── build.rs                # Asset copying build script
├── src/
│   ├── main.rs            # Application entry point
│   └── resource.rs        # Resource locator helpers
├── templates/             # Akari HTML templates
└── programfiles/          # Static assets (CSS, JS, images)

The build script automatically copies templates/ and programfiles/ to the target directory during compilation, making them accessible to your application at runtime.

🎯 Core Concepts

Endpoints

Define routes with the endpoint! macro:

endpoint! {
    APP.url("/users/<int:id>"),
    pub get_user<HTTP> {
        let user_id = req.param("id");
        json_response(json!({ "id": user_id }))
    }
}

Macro Notes

endpoint! and middleware! auto-register at startup (constructor-based), so there is no manual router.register() step.
Always use brace syntax {} and place doc comments inside the macro block.
Optional fn-style: pub fn name(req: HTTP) { ... }; angle-bracket form defaults to req.
Our philosophy is to wrap anything into macros to keep endpoints and middleware self-contained; see macro_ra.md for the minimal syntax and rationale.
Analyzer support is planned via custom analyzer tools.

Middleware

Create reusable middleware:

use htmstd::session::CookieSession;

pub static APP: SApp = Lazy::new(|| {
    App::new()
        .binding("127.0.0.1:3000")
        .append_middleware::<CookieSession>()
        .build()
});

Templates

Render HTML with Akari:

endpoint! {
    APP.url("/profile"),
    pub profile<HTTP> {
        let data = json!({ "name": "Alice" });
        template_response("profile.html", data)
    }
}

HTTP Safety Configuration

Configure request validation per endpoint:

endpoint! {
    APP.url("/upload"),
    config = [HttpSafety::new()
        .with_max_body_size(50 * 1024 * 1024)  // 50MB
        .with_allowed_methods(vec![HttpMethod::POST])
    ],
    pub upload<HTTP> {
        // Handle file upload
    }
}

Client Information

Access client IP addresses and connection details directly from your handlers:

endpoint! {
    APP.url("/api/whoami"),
    pub whoami<HTTP> {
        // Get client's full socket address (IP + port)
        match req.client_ip() {
            Some(addr) => text_response(format!("Your address: {}", addr)),
            None => text_response("Unknown client"),
        }
    }
}

Available Methods:

Method	Return Type	Description
`client_ip()`	`Option<SocketAddr>`	Client's socket address (IP + port)
`client_ip_or_default()`	`SocketAddr`	Returns `0.0.0.0:0` if unknown
`client_ip_only()`	`Option<IpAddr>`	Just the IP address, no port
`client_ip_only_or_default()`	`IpAddr`	Returns `0.0.0.0` if unknown
`server_addr()`	`Option<SocketAddr>`	Server's bound address
`remote_addr()`	`Option<SocketAddr>`	Alias for `client_ip()`
`local_addr()`	`Option<SocketAddr>`	Alias for `server_addr()`

Note: When behind a reverse proxy, client_ip() returns the proxy's address. Use headers like X-Forwarded-For or X-Real-IP to get the original client IP.

📚 Examples

Check out the example repository for:

Basic routing and handlers
Form processing and file uploads
Session management with cookies
CORS configuration
Multi-protocol applications

🔧 Crate Ecosystem

Hotaru is built on a modular architecture:

hotaru - Main framework with convenient API
hotaru_core - Core protocol and routing engine
hotaru_meta - Procedural macros for endpoint! and middleware!
hotaru_lib - Utility functions (compression, encoding, etc.)
htmstd - Standard middleware library (CORS, sessions)

📋 Changelog

0.7.x (Current)

Multi-protocol support (HTTP, WebSocket, custom TCP)
Enhanced security controls with HttpSafety
Improved middleware system with protocol inheritance
Performance optimizations in URL routing
Comprehensive security testing
.worker() method now properly configures dedicated worker threads per App instance
New LApp!, LUrl!, LPattern! macros for simplified lazy static declarations
Fixed hotaru new and hotaru init to generate correct endpoint! macro syntax
Built-in constructor implementation (no external ctor dependency required)
Client IP access: ctx.client_ip() and related methods for accessing socket addresses in handlers

0.6.x

Protocol abstraction layer
Request context improvements
Standard middleware library (htmstd)
Cookie-based session management

0.4.x and earlier

Async/await support with Tokio
Akari templating integration
Cookie manipulation APIs
File upload handling
Form data processing improvements

🔮 Schedule

Version No.	Content	Release Date (Approx.)
0.8.0	HTTP Outbound	Jan.2026
0.8.3	Using new template engine	Jan.2026
0.8.9	Bug Fixes	May.2026

📚 Learn More

Akari Template Engine: https://crates.io/crates/akari
Homepage: https://hotaru.rs
Documentation Home Page: https://fds.rs
GitHub: https://github.com/Field-of-Dreams-Studio/hotaru
Documentation: https://docs.rs/hotaru

Video Resources	URL
Quick Tutorial	Youtube: https://www.youtube.com/watch?v=8pV-o04GuKk&t=6s Bilibili: https://www.bilibili.com/video/BV1BamFB7E8n/

🤖 AI Declaration of each Mod

We believe in transparency about AI-assisted development. Below is an honest breakdown of AI involvement per module:

Name	Usage of AI	Comments
hotaru_core/app	Minimal
hotaru_core/connection	Some
hotaru_core/url	Minor
hotaru_core/http	Minor
hotaru_lib	Some	Basic API Access
hotaru_meta/endpoint	None
hotaru_meta/middleware	None
ahttpm	Major	Import Akari_macro and Improvements
h2per	Major	Integration of Hyper - Not stable yet
htmstd/cors	Minimal
htmstd/session	Minimal

Explanation of terms:

Term	Meaning
None	Full human code, no AI tools used
Minimal	AI used for autocompletion, minor suggestions, or documentation only
Minor	Some tabs. A few AI generated functions for logic. Testing code maybe written by AI
Some	Planning maybe done by AI. Overall structure written by human. Less than a third of real implementation written by AI
Major	Planning is done by AI. Overall structure generated by AI with supervision of human. More than a third of real implementation written by AI

📄 License

GPL-3.0 License

hotaru 0.7.7