README
¶
cmux
HTTP router for creating JSON APIs in Golang. Featuring built-in JSON handling and typesafe path variables etc.
Basic HTTP Request Handling
Handle methods like Get or Post. Methods with a request body like POST, must specify the data structure which the JSON should be encoded to, as a function parameter (e.g. cmux.Request[cmux.SomeRequestBody, *Metadatastruct] error {...). This data is then accessed from the Body field of cmux.Request.
func main() {
m := cmux.Mux{}
type PostData struct{
SomeValue string `json:"some_value"`
}
type Md struct{}
m.HandleFunc("/", &Md{},
cmux.Get(func(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return nil
}, nil),
cmux.Post(func(req *cmux.Request[PostData, *Md]) error {
fmt.Println("Received post value:", req.Body.SomeValue)
return nil
}, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Using Path Variables
Define path variables using curly brackets in the path and retrieve values by passing a struct to HandleFunc. The field tag "cmux" can be used to specify which path variable the field represents. Alternately path variables are saved to field names matching the path variable (case-insensitive). Path variables can have prefixes or suffixes. Note only one variable is supported per path section (i.e. between a pair of '/').
func main() {
m := cmux.Mux{}
type Md struct{
City string
StreetName string `cmux:"street"`
}
m.HandleFunc("/city-{city}/{street}", &Md{},
cmux.Get(func(req *cmux.Request[cmux.EmptyBody, *Md]) error {
fmt.Println("city:", req.Metadata.City, "street:", req.Metadata.StreetName)
return nil
}, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Responding
When a MethodHandler returns a type that implements the HTTPResponder interface (and the error interface), the HTTPRespond method is called and the response is encoded as JSON (unless an error is returned).
type Md struct {}
type Cake struct {
Name string `json:"name"`
StrawberryCount uint `json:"strawberry_count"`
}
func (c *Cake) HTTPRespond() (any, error) {
return c, nil
}
func (c *Cake) Error() string {
return "not filtered"
}
func GetCake(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return &Cake{
Name: "Large Strawberry Cake",
StrawberryCount: 5,
}
}
func main() {
m := cmux.Mux{}
m.HandleFunc("/get-cake", &Md{},
cmux.Get(GetCake, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Bypass
A type implementing the HTTP Response interface and the error interface can be returned directly in Methodhandler functions. This can be bypassed by using the mux.Bypass.
type Md struct {}
type Cake struct {
Name string `json:"name"`
StrawberryCount uint `json:"strawberry_count"`
}
func GetCake(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return cmux.Bypass(&Cake{
Name: "Large Strawberry Cake",
StrawberryCount: 5,
})
}
func main() {
m := cmux.Mux{}
m.HandleFunc("/get-cake", &Md{},
cmux.Get(GetCake, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Filter a response
HTTPRespond can also filter secret fields. This is useful when loading JSON documents from a database that contains fields that must not be publically available. In turn this allows the use of the same data structures.
type ResData struct {
PublicData string `json:"public_data"`
PrivateData string `json:"private_data,omitempty"`
}
func (r *ResData) HTTPRespond() (any, error) {
return &ResData{
PublicData: r.PublicData,
}, nil
}
func (r *ResData) Error() string {
return "not filtered"
}
func main() {
m := cmux.Mux{}
type Md struct{}
m.HandleFunc("/info", &Md{},
cmux.Get(func(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return &ResData{
PublicData: "some public data",
PrivateData: "some private data",
}
}, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Transform a response
type CreditCard struct {
CardNumber string `json:"card_number"`
}
func (cc *CreditCard) HTTPRespond() (any, error) {
var cardType string
if strings.HasPrefix(cc.CardNumber, "4") {
cardType = "visa"
} else if strings.HasPrefix(cc.CardNumber, "5") {
cardType = "mastercard"
} else {
return nil, cmux.HTTPError("unknown card type", 400)
}
return struct {
CardType string `json:"card_type"`
}{
CardType: cardType,
}, nil
}
func (r *CreditCard) Error() string {
return "not filtered"
}
func main() {
m := cmux.Mux{}
type Md struct{}
m.HandleFunc("/identify-card", &Md{},
cmux.Post(func(req *cmux.Request[CreditCard, *Md]) error {
return &req.Body
}, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Returning errors
HTTP errors can be returned directly using cmux.HTTPError(err string, code int) error or cmux.WrapError(err error, code int) error or by returning a type satisfying the HTTPErrorResponder interface.
type CustomError struct{}
func (ce *CustomError) HTTPError()(int, any) {
return 400, struct{
AlternateError string `json:"alternate_error"`
}{
AlternateError: "not good",
}
}
func (ce *CustomError) Error() string {
return "did not respond correctly to error"
}
func main() {
m := cmux.Mux{}
type PostData struct{
SomeValue string `json:"some_value"`
}
type Md struct{}
m.HandleFunc("/", &Md{},
cmux.Get(func(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return cmux.HTTPError("", http.StatusNotFound)
}, nil),
cmux.Post(func(wreq *cmux.Request[PostData, *Md]) error {
return cmux.WrapError(errors.New("something bad happened"), http.StatusInternalServerError)
}, nil),
cmux.Put(func(req *cmux.Request[PostData, *Md]) error {
return &CustomError{}
}, nil),
)
http.ListenAndServe("localhost:8080", &m)
}
Before and Method Handler Data
Each Method Handler can be passed a custom data argument, which is processed by the Mux's Before method. This could be a simple string for access control list or permissions handling or a struct containing more complex data. Here we require requests to ("http://localhost:8080/cities/{city}") to have pass a "{city}_mayor" token in the Token HTTP request header:
func main() {
type Md struct{
City string
}
m := cmux.Mux{
Before: func(req *http.Request, metadata, methodData any) error {
switch v := metadata.(type) {
case *Md:
permission, ok := methodData.(string)
if !ok {
panic("expected a permission string, got something else")
}
if req.Header.Get("token") != v.City + "_" + permission {
return cmux.HTTPError("", http.StatusForbidden)
}
default:
return fmt.Errorf("unexpected metadata type %T", v)
}
return nil
},
}
m.HandleFunc("/cities/{city}", &Md{},
cmux.Get(func(req *cmux.Request[cmux.EmptyBody, *Md]) error {
return nil
}, "mayor"),
)
http.ListenAndServe("localhost:8080", &m)
}
Performing the following curl command in a terminal will then yield a 200 response code:
curl -v localhost:8080/cities/london -H 'Token: london_mayor'
Documentation
¶
Index ¶
- Variables
- func HTTPError(err string, code int) error
- func HandleFunc(path string, metadata any, mhs ...MethodHandler)
- func WrapError(err error, code int) error
- type BypassingData
- type EmptyBody
- type HTTPErrorResponder
- type HTTPResponder
- type MethodHandler
- func Delete[I EmptyBody, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Get[I EmptyBody, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Head[I EmptyBody, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Options[I EmptyBody, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Patch[I any, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Post[I any, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Put[I any, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- func Trace[I EmptyBody, M any](fn func(*Request[I, M]) error, data any) MethodHandler
- type Mux
- func (mux *Mux) EnableDebug(enable bool)
- func (mux *Mux) EnableDebugTimings(enable bool)
- func (mux *Mux) HandleFunc(path string, metadata any, mhs ...MethodHandler)
- func (mux *Mux) Print(w io.Writer, indent string)
- func (mux *Mux) ServeHTTP(w http.ResponseWriter, r *http.Request)
- func (mux *Mux) SetDefaultContentType(ctype string)
- type PathParser
- type Request
Constants ¶
This section is empty.
Variables ¶
var DefaultMux = &Mux{}
Functions ¶
func HTTPError ¶
HTTPError creates an error that when returned in a MethodHandler makes the server reply with the specified error message and HTTP code.
func HandleFunc ¶
func HandleFunc(path string, metadata any, mhs ...MethodHandler)
Types ¶
type BypassingData ¶
type BypassingData struct {
// contains filtered or unexported fields
}
Bypassed data can be returned directly in method handler functions.
func Bypass ¶
func Bypass(res any) BypassingData
Bypass takes any data and transforms it into data that can be directly returned in method handler functions.
func (BypassingData) Error ¶
func (wd BypassingData) Error() string
func (BypassingData) HTTPRespond ¶
func (wd BypassingData) HTTPRespond() (any, error)
type HTTPErrorResponder ¶
Returning an error that also implements HTTPErrorResponder in a MethodHandler function will cause the server to call the HTTPError method and respond with the specified int as status code and JSON-encode the 'any' value as the body.
type HTTPResponder ¶
Returning an error that also implements HTTPResponder in a MethodHandler function will cause the server to call HTTPRespond and respond to the incoming request with the returned values. If the error is non-nil the response will be an error. If the error is nil, the response will be the JSON-encoded 'any' return value.
type MethodHandler ¶
type MethodHandler struct {
// contains filtered or unexported fields
}
MethodHandlers each handles a specific HTTP Method. They are returned by the functions Delete, Get, Head, Options, Patch, Post, Put, Trace.
type Mux ¶
type Mux struct {
Before func(http.ResponseWriter, *http.Request, any, any) error
// contains filtered or unexported fields
}
func (*Mux) EnableDebug ¶
func (*Mux) EnableDebugTimings ¶
func (*Mux) HandleFunc ¶
func (mux *Mux) HandleFunc(path string, metadata any, mhs ...MethodHandler)
HandleFunc handles requests matching the specified path in the speciified MethodHandlers. The metadata is copied for each new incoming request and can be mutated by the Mux.Before method before being available in the MethodHandler functions.
func (*Mux) SetDefaultContentType ¶
type PathParser ¶
type PathParser interface {
ParsePath()
}
type Request ¶
type Request[T any, M any] struct { Body T Metadata M /* Underlying native golang request / responsewriter: */ HTTPReq *http.Request ResponseWriter http.ResponseWriter }
Request stores incoming request data. Body contains the unmarshaled body of the request Metadata contains custom data that is passed to the HandleFunc and can be mutated by the mux Before Method. It also provides access to the underlying http.Request and http.ResponseWriter
Source Files