httpopenapi

httpopenapi

A lightweight adapter for the net/http package that automatically generates OpenAPI 3.x specifications from your routes using oaswrap/spec.

Features

• ⚡ Seamless Integration — Works with your existing net/http routes and handlers
• 📝 Automatic Documentation — Generate OpenAPI specs from route definitions and struct tags
• 🎯 Type Safety — Full Go type safety for OpenAPI configuration
• 🔧 Multiple UI Options — Swagger UI, Stoplight Elements, ReDoc, Scalar or RapiDoc served automatically at /docs
• 📄 YAML Export — OpenAPI spec available at /docs/openapi.yaml
• 🚀 Zero Overhead — Minimal performance impact on your API

Installation

go get github.com/oaswrap/spec/adapter/httpopenapi

Quick Start

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"time"

	"github.com/oaswrap/spec/adapter/httpopenapi"
	"github.com/oaswrap/spec/option"
)

func main() {
	mainMux := http.NewServeMux()
	r := httpopenapi.NewGenerator(mainMux,
		option.WithTitle("My API"),
		option.WithVersion("1.0.0"),
		option.WithSecurity("bearerAuth", option.SecurityHTTPBearer("Bearer")),
	)

	r.Route("/api/v1", func(r httpopenapi.Router) {
		r.HandleFunc("POST /login", LoginHandler).With(
			option.Summary("User login"),
			option.Request(new(LoginRequest)),
			option.Response(200, new(LoginResponse)),
		)
		auth := r.Group("/", AuthMiddleware).With(
			option.GroupSecurity("bearerAuth"),
		)
		auth.HandleFunc("GET /users/{id}", GetUserHandler).With(
			option.Summary("Get user by ID"),
			option.Request(new(GetUserRequest)),
			option.Response(200, new(User)),
		)
	})

	log.Printf("🚀 OpenAPI docs available at: %s", "http://localhost:3000/docs")

	// Start the server
	server := &http.Server{
		Handler:           mainMux,
		Addr:              ":3000",
		ReadHeaderTimeout: 5 * time.Second,
	}
	if err := server.ListenAndServe(); err != nil {
		log.Fatal(err)
	}
}

type LoginRequest struct {
	Username string `json:"username" required:"true"`
	Password string `json:"password" required:"true"`
}

type LoginResponse struct {
	Token string `json:"token"`
}

type GetUserRequest struct {
	ID string `path:"id" required:"true"`
}

type User struct {
	ID   string `json:"id"`
	Name string `json:"name"`
}

func AuthMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Simulate authentication logic
		authHeader := r.Header.Get("Authorization")
		if authHeader != "" && authHeader == "Bearer example-token" {
			next.ServeHTTP(w, r)
		} else {
			http.Error(w, "Unauthorized", http.StatusUnauthorized)
		}
	})
}

func LoginHandler(w http.ResponseWriter, r *http.Request) {
	var req LoginRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid request", http.StatusBadRequest)
		return
	}
	// Simulate login logic
	_ = json.NewEncoder(w).Encode(LoginResponse{Token: "example-token"})
}

func GetUserHandler(w http.ResponseWriter, r *http.Request) {
	var req GetUserRequest
	id := r.PathValue("id")
	if id == "" {
		http.Error(w, "User ID is required", http.StatusBadRequest)
		return
	}
	req.ID = id
	// Simulate fetching user by ID
	user := User{ID: req.ID, Name: "John Doe"}
	_ = json.NewEncoder(w).Encode(user)
}

Documentation Features

Built-in Endpoints

When you create a httpopenapi router, the following endpoints are automatically available:

• /docs — Interactive UI documentation
• /docs/openapi.yaml — Raw OpenAPI specification in YAML format

If you want to disable the built-in UI, you can do so by passing option.WithDisableDocs() when creating the router:

r := httpopenapi.NewRouter(c,
	option.WithTitle("My API"),
	option.WithVersion("1.0.0"),
	option.WithDisableDocs(),
)

Supported Documentation UIs

Choose from multiple UI options, powered by oaswrap/spec-ui:

• Stoplight Elements — Modern, clean design (default)
• Swagger UI — Classic interface with try-it functionality
• ReDoc — Three-panel responsive layout
• Scalar — Beautiful and fast interface
• RapiDoc — Highly customizable

r := httpopenapi.NewRouter(c,
	option.WithTitle("My API"),
	option.WithVersion("1.0.0"),
	option.WithScalar(), // Use Scalar as the documentation UI
)

Rich Schema Documentation

Use struct tags to generate detailed OpenAPI schemas. Note: These tags are used only for OpenAPI spec generation and documentation - they do not perform actual request validation.

type CreateProductRequest struct {
	Name        string   `json:"name" required:"true" minLength:"1" maxLength:"100"`
	Description string   `json:"description" maxLength:"500"`
	Price       float64  `json:"price" required:"true" minimum:"0" maximum:"999999.99"`
	Category    string   `json:"category" required:"true" enum:"electronics,books,clothing"`
	Tags        []string `json:"tags" maxItems:"10"`
	InStock     bool     `json:"in_stock" default:"true"`
}

For more struct tag options, see the swaggest/openapi-go.

Examples

Check out complete examples in the main repository:

• Basic

Best Practices

1. Organize with Tags — Group related operations using option.Tags()
2. Document Everything — Use option.Summary() and option.Description() for all routes
3. Define Error Responses — Include common error responses (400, 401, 404, 500)
4. Use Validation Tags — Leverage struct tags for request validation documentation
5. Security First — Define and apply appropriate security schemes
6. Version Your API — Use route groups for API versioning (/api/v1, /api/v2)

API Reference

• Spec: pkg.go.dev/github.com/oaswrap/spec
• HTTP Adapter: pkg.go.dev/github.com/oaswrap/spec/adapter/httpopenapi
• Options: pkg.go.dev/github.com/oaswrap/spec/option
• Spec UI: pkg.go.dev/github.com/oaswrap/spec-ui

Contributing

We welcome contributions! Please open issues and PRs at the main oaswrap/spec repository.

License

MIT