Skip to content

REST Servers

Codcel generates REST API servers that expose your Excel calculations as HTTP endpoints. Each calculation method becomes a POST endpoint that accepts JSON input and returns JSON output.

Rust Server

  • Build system: Cargo
  • Framework: Axum
  • Build: cargo build --release
  • Run: cargo run
  • Default port: 3030
  • Dependencies: axum, tokio, serde, tower-http (CORS)

The Rust server is the recommended option for production deployments. It has the smallest footprint and best performance.

Java Server

  • Build system: Gradle
  • Framework: Javalin 6
  • Prerequisites: JDK 11+
  • Build: ./gradlew build
  • Run: ./gradlew run
  • Default port: 7000
  • Custom port: ./gradlew run -Pport=8080
  • Bridge: JNI -- requires the JNI library to be built first

Kotlin Server

  • Build system: Gradle with Kotlin plugin
  • Framework: Javalin 6
  • Prerequisites: JDK 17+ (toolchain 21 configured)
  • Build: ./gradlew build
  • Run: ./gradlew run
  • Default port: 7000
  • Custom port: ./gradlew run -Pport=8080
  • Bridge: JNI -- requires the JNI library to be built first

C# Server

  • Build system: .NET 8.0 (ASP.NET Core)
  • Prerequisites: .NET 8 SDK
  • Run: dotnet run -p:CodcelTargetOS=<os>
  • Custom port: dotnet run --urls http://localhost:8000 -p:CodcelTargetOS=<os>
  • OS parameter: linux, macos, or windows
  • Bridge: FFI -- requires the FFI library to be built first

Go Server

  • Build system: Go Modules
  • Framework: Gorilla Mux
  • Prerequisites: Go 1.21+; TDM-GCC on Windows (for CGO)
  • Build/Run: go run .
  • Default port: 8080
  • Custom port: go run . --port=3000
  • Build scripts: build_and_test_sh.sh, build_and_test_ps1.ps1
  • Bridge: FFI -- requires the FFI library to be built first

API Endpoints

Each server generates one POST endpoint per calculation method defined in your Excel workbook. For example, if your workbook defines a calculation called monthly_payment, the server exposes:

POST /monthly_payment
Content-Type: application/json

{
  "interest_rate": 5.5,
  "loan_amount": 250000,
  "term_years": 30
}

Response:

{
  "monthly_payment": 1419.47
}

All servers support CORS, allowing browser-based clients to call the API directly.

Accept-Language Header

All generated servers accept an optional Accept-Language HTTP header. When present, the server applies locale-appropriate number and currency formatting for that request. For example, sending Accept-Language: de formats numbers with a comma as the decimal separator.

See Runtime Formatting for details.

Default Ports

Server Default Port
Rust 3030
Java 7000
Kotlin 7000
C# 5000
Go 8080

OpenAPI Documentation

When you generate the OpenAPI Document target, a open-api.json file is produced. This is an OpenAPI 3.0.3 specification describing all endpoints, request/response schemas, and server URLs. You can import this into tools like Swagger UI, Postman, or any API documentation tool.

See Integrations for more details.