Oat++ — Zero-Dependency C++ Web Framework

Introduction

Oat++ is a modern C++ web framework designed for high-performance HTTP services with zero external dependencies. It provides object mapping, Swagger integration, and connection handling out of the box, making it practical for production C++ APIs and microservices.

What Oat++ Does

• Serves HTTP/1.1 requests with async and blocking execution models
• Maps C++ objects to JSON and back using code-generated DTOs
• Provides built-in Swagger/OpenAPI documentation generation
• Supports WebSocket connections for real-time communication
• Handles database interaction through typed ORM-style query builders

Architecture Overview

Oat++ uses a layered design: an HTTP connection handler dispatches to a router, which maps requests to controller endpoints. Data Transfer Objects (DTOs) define typed request and response bodies. The framework compiles without any third-party library, relying only on the C++ standard library and OS sockets.

Self-Hosting & Configuration

• Build from source with CMake; no package manager dependencies needed
• Define API endpoints in controller classes using macro-based routing
• Configure server port, connection limits, and threading in the AppComponent
• Enable Swagger UI by adding the oatpp-swagger module
• Choose between simple (blocking) and async (coroutine-based) server modes

Key Features

• Truly zero external dependencies; compiles on any platform with a C++11 compiler
• Built-in Swagger UI generation from annotated endpoints
• Async server mode using coroutines for high-concurrency scenarios
• Typed DTO system catches serialization mismatches at compile time
• Modular ecosystem with extensions for PostgreSQL, SQLite, WebSocket, and more

Comparison with Similar Tools

• Drogon — Drogon offers similar performance with a broader async ecosystem; Oat++ emphasizes zero dependencies and simpler bootstrapping
• Crow — Crow is a microframework with Flask-like simplicity; Oat++ provides more structure with DTOs and Swagger support
• cpp-httplib — cpp-httplib is header-only for simple cases; Oat++ adds routing, serialization, and API documentation
• Pistache — Pistache focuses on REST; Oat++ extends to WebSocket and database layers

FAQ

Q: Does Oat++ require Boost or any other library? A: No. Oat++ has zero external dependencies. Optional modules like oatpp-postgresql add specific integrations.

Q: How does Oat++ handle JSON serialization? A: You define DTO classes with macros like DTO_FIELD. The framework generates serializers that map between C++ objects and JSON automatically.

Q: Is Oat++ suitable for production use? A: Yes. Oat++ is used in production services and benchmarks competitively with other C++ frameworks.

Q: What platforms does Oat++ support? A: Linux, macOS, Windows, and FreeBSD. Any platform with a C++11 compiler and POSIX or WinSock sockets.

Sources

• https://github.com/oatpp/oatpp
• https://oatpp.io/docs/start/