Servant
Servant is a Haskell library for defining type-safe web APIs and deriving corresponding server and client implementations.
Learn Haskell by Example
Servant is a Haskell library ecosystem for defining type-safe web APIs and generating server and client implementations from API descriptions.
- How it is used
- Defines a todo-list HTTP/JSON API, implements its server, and derives a CLI-facing client from one API description.
- How deep it goes
- Works through API operators, concrete handlers, HTTP errors, middleware, and generated clients, while deferring the internals of DataKinds and TypeOperators.
- Examples
- Builds a todo API with entries, add, and toggle endpoints, database-backed handlers, a root HTML route, and derived client actions.
- What you can do after
- Apply it via Servant to specify a typed HTTP API, assemble matching handlers, add middleware, and derive client functions.
Functional Design and Architecture: Examples in Haskell
servant-client is a Haskell library that derives client functions for making HTTP requests from Servant API specifications.
- How it is used
- Deploys typed HTTP clients and RESTful servers while keeping business logic independent of the communication channel.
- How deep it goes
- Explains type-level API schemas, generated client actions, and framework integration, but leaves uncommon requirements such as streaming difficult.
- Examples
- Uses meteor and asteroid POST endpoints, JSON payload types, generated ClientM functions, and reporting-error conversion.
- What you can do after
- Build it from scratch: define a shared API type and derive client operations for framework-managed HTTP requests.
Read how Functional Design and Architecture: Examples in Haskell explains Servant →
Related concepts
- contractproduces · An API contract is a specification of the operations, data, and behavioral expectations that govern interactions between software components.
- Applicationproduces · In WAI, an Application is a low-level HTTP interface that receives a request and produces a response.
- embedded domain-specific languagekind of · An embedded domain-specific language is a language tailored to a particular problem domain and expressed within a host programming language.
- type-safe APIimplements · A type-safe API is an application programming interface whose operations, inputs, and outputs are specified and checked to prevent invalid type combinations.
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