CRUD

Una API CRUD (create, read, update, delete) completa respaldada por un store en memoria. Los handlers vinculan el body JSON del request a un struct, acceden al store bajo un lock y devuelven JSON. Un usuario inexistente devuelve 404, y un id inválido o un nombre vacío devuelve 400.

Servidor

cookbook/crud/server.go

package main

import (
  "cmp"
  "context"
  "net/http"
  "slices"
  "strings"
  "sync"

  "github.com/labstack/echo/v5"
  "github.com/labstack/echo/v5/middleware"
)

type (
  user struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
  }
)

var (
  users = map[int]user{}
  seq   = 1
  lock  = sync.Mutex{}
)

//----------
// Handlers
//----------

// The store holds user values, so handlers copy a user under the lock and write the response after unlocking.

func createUser(c *echo.Context) error {
  u, err := bindUser(c)
  if err != nil {
    return err
  }
  lock.Lock()
  // Assign the ID after binding so an "id" in the request body cannot overwrite another user.
  u.ID = seq
  users[u.ID] = u
  seq++
  lock.Unlock()
  return c.JSON(http.StatusCreated, u)
}

func getUser(c *echo.Context) error {
  id, err := userID(c)
  if err != nil {
    return err
  }
  lock.Lock()
  u, ok := users[id]
  lock.Unlock()
  if !ok {
    return echo.NewHTTPError(http.StatusNotFound, "user not found")
  }
  return c.JSON(http.StatusOK, u)
}

func updateUser(c *echo.Context) error {
  id, err := userID(c)
  if err != nil {
    return err
  }
  u, err := bindUser(c)
  if err != nil {
    return err
  }
  lock.Lock()
  existing, ok := users[id]
  if ok {
    existing.Name = u.Name
    users[id] = existing
  }
  lock.Unlock()
  if !ok {
    return echo.NewHTTPError(http.StatusNotFound, "user not found")
  }
  return c.JSON(http.StatusOK, existing)
}

func deleteUser(c *echo.Context) error {
  id, err := userID(c)
  if err != nil {
    return err
  }
  lock.Lock()
  _, ok := users[id]
  delete(users, id)
  lock.Unlock()
  if !ok {
    return echo.NewHTTPError(http.StatusNotFound, "user not found")
  }
  return c.NoContent(http.StatusNoContent)
}

func getAllUsers(c *echo.Context) error {
  lock.Lock()
  list := make([]user, 0, len(users)) // non-nil, so an empty store returns [] rather than null
  for _, u := range users {
    list = append(list, u)
  }
  lock.Unlock()
  slices.SortFunc(list, func(a, b user) int { return cmp.Compare(a.ID, b.ID) })
  return c.JSON(http.StatusOK, list)
}

// bindUser binds the JSON request body and requires a non-blank name.
func bindUser(c *echo.Context) (user, error) {
  var u user
  if err := c.Bind(&u); err != nil {
    return u, err
  }
  if strings.TrimSpace(u.Name) == "" {
    return u, echo.NewHTTPError(http.StatusBadRequest, "name is required")
  }
  return u, nil
}

// userID returns the :id path parameter, or a 400 error when it is not a number.
func userID(c *echo.Context) (int, error) {
  id, err := echo.PathParam[int](c, "id")
  if err != nil {
    return 0, echo.NewHTTPError(http.StatusBadRequest, "invalid user id")
  }
  return id, nil
}

func newServer() *echo.Echo {
  e := echo.New()

  // Middleware
  e.Use(middleware.RequestLogger())
  e.Use(middleware.Recover())

  // Routes
  e.GET("/users", getAllUsers)
  e.POST("/users", createUser)
  e.GET("/users/:id", getUser)
  e.PUT("/users/:id", updateUser)
  e.DELETE("/users/:id", deleteUser)
  return e
}

func main() {
  e := newServer()

  // Start server
  sc := echo.StartConfig{Address: ":1323"}
  if err := sc.Start(context.Background(), e); err != nil {
    e.Logger.Error("failed to start server", "error", err)
  }
}

Cliente

Crear usuario

Request:

curl -X POST \
  -H 'Content-Type: application/json' \
  -d '{"name":"Joe Smith"}' \
  localhost:1323/users

Response:

{
  "id": 1,
  "name": "Joe Smith"
}

Obtener usuario

Request:

curl localhost:1323/users/1

Response:

{
  "id": 1,
  "name": "Joe Smith"
}

Listar usuarios

Request:

curl localhost:1323/users

Response:

[
  {
    "id": 1,
    "name": "Joe Smith"
  }
]

Actualizar usuario

Request:

curl -X PUT \
  -H 'Content-Type: application/json' \
  -d '{"name":"Joe"}' \
  localhost:1323/users/1

Response:

{
  "id": 1,
  "name": "Joe"
}

Eliminar usuario

Request:

curl -X DELETE localhost:1323/users/1

Response: 204 No Content.

Usuario inexistente

Request:

curl localhost:1323/users/9999

Response (404 Not Found):

{
  "message": "user not found"
}