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.