revel-apikit

A way to rapidly develop REST APIs using the Revel framework

Goal

Writing controllers for a Revel REST API can get repetitive. You might find yourself writing Get(), Create(), Update(), and Delete() for every model in your database.

This package tries to abstract away that CRUD boilerplate. The following is an example of how you might implement a controller for just one of your models, a User:

type UserController struct
  *revel.Controller
  authenticatedUser *User
}

func (c *UserController) Get(id uint64) revel.Result {
	if user := GetUserByID(id); user == nil {
		return ApiMessage{
			StatusCode: http.StatusNotFound,
			Message: fmt.Sprint("User with ID ", id, " not found"),
		}
	} else if !user.CanBeViewedBy(c.authenticatedUser) {
		return ApiMessage{
			StatusCode: http.StatusUnauthorized,
			Message: fmt.Sprint("Unauthorized to view User with ID ", id),
		}
	} else {
		return c.RenderJson(user)
	}
}

func (c *UserController) Post() revel.Result {
	newUser := User{}
	err := json.NewDecoder(c.Request.Body).Decode(&newUser)
	if err != nil {
			return ApiMessage{
				StatusCode: http.StatusBadRequest,
				Message: "Improperly formatted request body",
			}
	}
	
	if !newUser.CanBeModifiedBy(c.authenticatedUser) {
		return ApiMessage{
			StatusCode: http.StatusUnauthorized,
			Message: "Not authorized to post this User",
		}
	}
	if err = newUser.Save(); err != nil {
		return ApiMessage{
			StatusCode: http.StatusBadRequest,
			Message: err.Error(),
		}
	} else {
		return c.RenderJson(newUser)
	}
}

func (c *UserController) Put() revel.Result {
	updatedUser := User{}
	err := json.NewDecoder(c.Request.Body).Decode(&updatedUser)
	if err != nil {
			return ApiMessage{
				StatusCode: http.StatusBadRequest,
				Message: "Improperly formatted request body",
			}
	}

	if !updatedUser.CanBeModifiedBy(c.authenticatedUser) {
		return ApiMessage{
			StatusCode: http.StatusUnauthorized,
			Message: "Not authorized to modify this User",
		}
	}
	if err = updatedUser.Save(); err != nil {
		return ApiMessage{
			StatusCode: http.StatusBadRequest,
			Message: err.Error(),
		}
	} else {
		return c.RenderJson(updatedUser)
	}
}

func (c *UserController) Delete(id uint64) revel.Result {
	if user := GetUserByID(id); user == nil {
		return ApiMessage{
			StatusCode: http.StatusNotFound,
			Message: fmt.Sprint("User with ID ", id, " not found"),
		}
	} else {
		if !user.CanBeModifiedBy(c.authenticatedUser) {
			return ApiMessage{
				StatusCode: http.StatusUnauthorized,
				Message: "Not authorized to delete this User",
			}
		}
		if err := user.Delete(); err != nil {
			return ApiMessage{
				StatusCode: http.StatusBadRequest,
				Message: err.Error(),
			}
		} else {
			return ApiMessage{
				StatusCode: http.StatusOK,
				Message: "Success",
			}
		}
	}
}

The best way to solve this problem would be to create a generic struct, but since Go does not currently support generics, this package tries to emulate a generic class using interfaces.

With this package, you can gain all of the above functionality by embeding a GenericRESTController within a Revel controller that implements the RESTController interface. The RESTController interface serves as a workaround for Go's lack of generics. Using it gives you all of the above functionality with only the following code:

type UserController struct {
  *revel.Controller
  apikit.GenericRESTController
}

func (c *UserController) ModelFactory() RESTObject {
	return &User{}
}

func (c *UserController) GetModelByID(id uint64) RESTObject {
	for _, u := range usersDB {
		if u.ID == id {
			return u
		}
	}
	return nil
}

Doing this will allow your UserController to serve the following Revel routes:

# UserController
GET     /users/:id                              UserController.Get
POST    /users                                  UserController.Post
PUT     /users                                  UserController.Put
DELETE  /users/:id                              UserController.Delete

Limitations

• RESTController instances cannot have Actions other than those provided by GenericRESTController
• conf/restcontroller-routes cannot use catchall : Actions
• conf/restcontroller-routes cannot use wildcard * paths