Difference between http.Handle and http.HandleFunc?

Question

The Go docs have the following example for the http package:

http.Handle(\"/foo\", fooHandler)
http.HandleFunc(\"/bar\", func(w http.ResponseWriter, r *http.         


        

Answer 1

No It's Different. Let's Examine

func Handle(pattern string, handler Handler) {
    DefaultServeMux.Handle(pattern, handler) 
}

handle expects us to pass a Handler. Handler is an interface

type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}

if any type implements ServeHTTP(ResponseWriter, *Request) for example: myCustomHandler then we can pass it like Handle(pattern string, myCustomHandler).

In the second scenario:

HandleFunc(pattern string, func(w ResponseWriter, r *Request) {
    // do some stuff
}

HandleFunc expects a function where Handle expects a Handler interface.

So, if you just want to pass a function then you can use http.HandleFunc(..). Like @David showed that behind the scenes it implements Handler interface by calling ServeHTTP.

type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
    f(w, r)
}

Answer 2

Basically, the HTTP server's "mux" has a map of path -> handler interface

Interfaces are used here, I assume, to allow you to implement complex path handlers that have state.

For example the file server from the standard package is a struct that contains the root dir for file service and implements the handler interface.

that said, for simple stuff, a func is easier and more clear. So they added a special generator so you can easily pass in a func.

Take a look at: server.go

from line: 1216 (as of today)

  1216  type HandlerFunc func(ResponseWriter, *Request)
  1217  
  1218  // ServeHTTP calls f(w, r).
  1219  func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
  1220      f(w, r)
  1221  }

What they are doing is implementing the interface on a custom type (which happens to match the api of the interface) that just calls itself.

Answer 3

Very correct answers so I won't say much but explain it in simple terms:

Problem: I want to create an object (type) that responds to HTTP requests.

Solution: use http.Handle and the object you create should implement ServeHTTP interface from the HTTP package.

Problem: I want a function to respond to my HTTP request.

Solution: Use http.HandleFunc for that and register your function with the HTTP server.