JSON API Route

Verified Scenario

This page is generated from an executable spec. An automated suite renders a fresh App from the current GoForj templates, applies every step below in order, and runs every verification command. If any step fails, the page does not ship.

Scenario 1 of 7 in the verified path. Plan on about 15 minutes.

This scenario adds a GET /api/v1/users/:id endpoint to a generated GoForj App.

The endpoint is intentionally small. It establishes the normal shape for application features: start from the make command, keep the controller thin, put behavior behind a service, register providers explicitly, and verify the route through the generated runtime.

What You Will Build

• internal/users.Service owns user lookup behavior.
• internal/users.Controller translates HTTP into a service call.
• forj make:controller users creates the controller wiring and route registration.
• appSet in app/wire provides the service.
• forj route:list shows the registered endpoint.

Prerequisites

Start from a generated GoForj App with HTTP enabled.

Golden Path State

Before this scenario, the App has the generated HTTP runtime but no application-owned user feature.

After this scenario, the App has one tested GET /api/v1/users/:id route, a thin controller, a service boundary, Wire providers, and route registration that appears in route:list.

Files

This scenario edits or creates:

Users feature

internal/users/service.go
internal/users/service_test.go
internal/users/controller.go

HTTP registration

app/wire/inject_http_controllers_app.go
app/routes.go

App wiring

app/wire/inject_services_app.go

Step 1: Scaffold the Controller

Start with the real make command. It creates internal/users/controller.go, wires the controller constructor into app/wire/inject_http_controllers_app.go, and adds the controller routes to app/routes.go.

forj make:controller users

Step 2: Add the Service

Create internal/users/service.go.

The service owns application behavior. This first version is intentionally simple and keeps persistence out of the HTTP boundary.

Create or replace internal/users/service.go:

// Package users keeps user behavior independent from HTTP and infrastructure details.
package users

import (
	"context"
	"errors"
)

// ErrUserNotFound lets transports handle missing users without depending on repository details.
var ErrUserNotFound = errors.New("user not found")

// User keeps the application response independent from transport and persistence models.
type User struct {
	ID    string `json:"id"`
	Name  string `json:"name"`
	Email string `json:"email"`
}

// Service keeps user lookup rules outside the HTTP controller.
type Service struct{}

// NewService keeps construction explicit so Wire and tests use the same entry point.
func NewService() *Service {
	return &Service{}
}

// Find centralizes lookup rules so transports do not duplicate input behavior.
func (*Service) Find(_ context.Context, id string) (User, error) {
	if id == "" {
		return User{}, ErrUserNotFound
	}

	return User{
		ID:    id,
		Name:  "Ada Lovelace",
		Email: "ada@example.test",
	}, nil
}

Step 3: Replace the Starter Controller

Replace internal/users/controller.go.

Keep the generated controller registration, but replace the starter handler with a service-backed GET /users/:id route.

The controller only reads HTTP input, calls the service, and writes the HTTP response. It does not own persistence, cache behavior, queue dispatch, or infrastructure setup.

Create or replace internal/users/controller.go:

// Package users keeps HTTP translation separate from user lookup behavior.
package users

import (
	"errors"
	"net/http"

	"github.com/goforj/web"
)

// Controller keeps HTTP translation separate from user lookup behavior.
type Controller struct {
	service *Service
}

// NewController makes the service dependency explicit for Wire and focused tests.
func NewController(service *Service) *Controller {
	return &Controller{service: service}
}

// Routes keeps the users HTTP surface discoverable by the App router.
func (c *Controller) Routes() []web.Route {
	return []web.Route{
		web.NewRoute(http.MethodGet, "/users/:id", c.Show),
	}
}

// Show translates the service result into the public HTTP contract.
func (c *Controller) Show(ctx web.Context) error {
	user, err := c.service.Find(ctx.Context(), ctx.Param("id"))
	if errors.Is(err, ErrUserNotFound) {
		return ctx.JSON(http.StatusNotFound, map[string]string{
			"error": "user not found",
		})
	}
	if err != nil {
		return err
	}

	return ctx.JSON(http.StatusOK, user)
}

Step 4: Provide the Service

Open app/wire/inject_services_app.go.

Wire can already construct the controller after the make command, but the controller now needs *users.Service. Add the users package to the imports, using your App module path.

Update app/wire/inject_services_app.go so it includes:

	"your/module/internal/runtime"
	"your/module/internal/users"

Step 5: Add the Service Provider

Add users.NewService to appSet.

Service is now part of the compiled App dependency graph, and Wire can construct the controller because appSet provides *users.Service.

Update app/wire/inject_services_app.go so it includes:

users.NewService,
app.NewLifecycleRegistry,

Step 6: Add a Service Test

Create internal/users/service_test.go.

The service test does not start HTTP. It proves the business behavior directly.

Create or replace internal/users/service_test.go:

// Package users keeps lookup behavior testable without starting the HTTP runtime.
package users

import (
	"context"
	"errors"
	"testing"
)

// TestServiceFindsUser protects lookup behavior without involving HTTP wiring.
func TestServiceFindsUser(t *testing.T) {
	service := NewService()
	want := User{
		ID:    "42",
		Name:  "Ada Lovelace",
		Email: "ada@example.test",
	}

	user, err := service.Find(context.Background(), "42")
	if err != nil {
		t.Fatalf("find user: %v", err)
	}
	if user != want {
		t.Fatalf("user = %+v, want %+v", user, want)
	}
}

// TestServiceRejectsEmptyID keeps missing identifiers from becoming valid lookups.
func TestServiceRejectsEmptyID(t *testing.T) {
	service := NewService()

	_, err := service.Find(context.Background(), "")
	if !errors.Is(err, ErrUserNotFound) {
		t.Fatalf("find user error = %v, want %v", err, ErrUserNotFound)
	}
}

Build and Verify

forj build

go test ./...

forj route:list

Expected output includes:

• /api/v1/users/:id

Try the Route

Run the HTTP server:

forj api

Request the endpoint:

curl http://localhost:3000/api/v1/users/42

Expected response:

{"id":"42","name":"Ada Lovelace","email":"ada@example.test"}

Operations

Operational notes:

• route:list shows it after registration.
• HTTP request logs include requests to it when access logging is enabled.
• HTTP metrics include it when metrics are enabled.
• HTTP inspects can show request and response details when inspect capture is enabled.
• Lighthouse can display route and runtime information when Lighthouse is enabled.

Common Mistakes

Common mistakes

• Do not put user lookup logic in Show.
• Do not register routes directly in the HTTP server package.
• Do not edit app/wire/wire_gen.go by hand.
• Do not skip forj build after changing Wire providers.
• Do not import the underlying HTTP engine in normal App controllers.

Next Steps

• Next, extend this feature with a repository and named cache resource in Cached User Profile.
• Controllers explains handler structure.
• Wiring Recipes shows where providers belong.