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Input Adapters(Hexagonal Architecture)

Information

Input Adapters, also known as driving or secondary, are implementation of the entry points of the application like HTTP/gRPC handlers, UI, or tests. They are responsible for calling Business Logic using ports, often translating requests from the outside world into Domain Objects.

Often used input adapters:

  1. server - http, grpc, websockets, graphQL, ...
  2. queue workers - kafka, rabbitmq, ...
  3. tests,
  4. console commands,
  5. UI.

Input Adapters are kind of Adapter and they are part of Hexagonal Architecture.

Hexagonal Architecture

Examples

All examples below are implementations of input adapters.

Server

HTTP handler for graph translation:

func (h *Handler) Translate(rw http.ResponseWriter, req *http.Request){
  inputGraph, err := h.converter.Convert(req.Body)
  if err ...

	// calling into Business Logic using port(interface)
  outputGraph, err := h.translator.Translate(inputGraph)
  if err ...

  writeResponse(rw, outputGraph)
}

// main
handler := handlerTranslator.New(...)
router.POST("/translate", handler.Translate)

Command

Console command for graph translation:

// main
...
data, err := os.ReadFile(cfg.GraphPath)
if err ...

var inputGraph domain.InputGraph

err := json.Unmarshal(data, &inputGraph)
if err ...


// calling into Business Logic using port(interface)
outputGraph, err := translator.Translate(inputGraph)
if err ...

fmt.Prinln(outputGraph)

Tests

This is part of a testing suite responsible for creating mocks and running the Consume Business Logic:

func (f *apiFeature) processTheMessage() error {
  dpRepoMock, segmentRepoMock := createMocks(...)

  set := build.FlexibleSet(
      f.cfg, dpRepoMock, segmentRepoMock,
  )

  message := attribute.AttrChangeMsg{}

  err := json.Unmarshal([]byte(f.message), &message)
  if err ...

	// calling into Business Logic using port(interface)
  return set.Consumer.Consume(message)
}

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