Request handling
Error Handling
An error is Go way to tell something went wrong. In this chapter, you’ll learn how to return errors from a route handler and how Buffalo will catch any non-handled error.
Returning Errors From a Handler
The easiest way to produce an error response is to return a standard Go error:
func MyHandler(c buffalo.Context) error {
// Return any go error, this will result in a 500 status code.
return errors.New("boom!")
}
A nil error will produce a raw HTTP 200 response:
func MyHandler(c buffalo.Context) error {
// HTTP 200
return nil
}
If you need to customize the error message or the HTTP code, use the Error method:
func MyHandler(c buffalo.Context) error {
// Use the Error function on the context.
// This will result in a status code of 401.
return c.Error(401, errors.New("Unauthorized!"))
}
Default Error Handling (Development)
In “development” mode (GO_ENV=development), Buffalo will generate some helpful errors pages for you.
If you use a JSON or an XML content type, the error is returned in the proper type:
{
"error": "could not find test/",
"trace": "could not find test/\ngithub.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo.(*App).fileServer.func1\n\t/home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo/route_mappings.go:97\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:1947\nnet/http.StripPrefix.func1\n\t/usr/local/go/src/net/http/server.go:1986\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:1947\ngithub.com/gobuffalo/docs/vendor/github.com/gorilla/mux.(*Router).ServeHTTP\n\t/home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gorilla/mux/mux.go:162\ngithub.com/gobuffalo/docs/vendor/github.com/markbates/refresh/refresh/web.ErrorChecker.func1\n\t/home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/markbates/refresh/refresh/web/web.go:23\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:1947\ngithub.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo.(*App).ServeHTTP\n\t/home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo/server.go:127\nnet/http.serverHandler.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2694\nnet/http.(*conn).serve\n\t/usr/local/go/src/net/http/server.go:1830\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:2361",
"code": 404
}
<response code="404">
<error>could not find test/</error>
<trace>could not find test/ github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo.(*App).fileServer.func1 /home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo/route_mappings.go:97 net/http.HandlerFunc.ServeHTTP /usr/local/go/src/net/http/server.go:1947 net/http.StripPrefix.func1 /usr/local/go/src/net/http/server.go:1986 net/http.HandlerFunc.ServeHTTP /usr/local/go/src/net/http/server.go:1947 github.com/gobuffalo/docs/vendor/github.com/gorilla/mux.(*Router).ServeHTTP /home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gorilla/mux/mux.go:162 github.com/gobuffalo/docs/vendor/github.com/markbates/refresh/refresh/web.ErrorChecker.func1 /home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/markbates/refresh/refresh/web/web.go:23 net/http.HandlerFunc.ServeHTTP /usr/local/go/src/net/http/server.go:1947 github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo.(*App).ServeHTTP /home/michalakst/go/src/github.com/gobuffalo/docs/vendor/github.com/gobuffalo/buffalo/server.go:127 net/http.serverHandler.ServeHTTP /usr/local/go/src/net/http/server.go:2694 net/http.(*conn).serve /usr/local/go/src/net/http/server.go:1830 runtime.goexit /usr/local/go/src/runtime/asm_amd64.s:2361</trace>
</response>
In “production” mode (GO_ENV=production), Buffalo will not generate pages that have developer style information, because this would give precious information to hackers. Instead the pages are simpler.
Custom Error Handling
While Buffalo will handle errors for you out of the box, it can be useful to handle errors in a custom way. To accomplish this, Buffalo allows for the mapping of HTTP status codes to specific handlers. This means the error can be dealt with in a custom fashion.
app = buffalo.New(buffalo.Options{
Env: ENV,
})
// We associate the HTTP 422 status to a specific handler.
// All the other status code will still use the default handler provided by Buffalo.
app.ErrorHandlers[422] = func(status int, err error, c buffalo.Context) error {
res := c.Response()
res.WriteHeader(422)
res.Write([]byte(fmt.Sprintf("Oops!! There was an error: %s", err.Error())))
return nil
}
app.GET("/oops", MyHandler)
func MyHandler(c buffalo.Context) error {
return c.Error(422, errors.New("Oh no!"))
}
GET /oops -> [422] Oops!! There was an error: Oh no!
In the above example any error from your application that returns a status of 422 will be caught by the custom handler and will be dealt with accordingly.