router

1. router in golang

1). sample code

 1 package main
 2
 3 import (
 4     "fmt"
 5     "net/http"
 6 )
 7
 8 func main() {
 9
10     http.HandleFunc("/handlefunc", func(w http.ResponseWriter, r *http.Request) {
11         fmt.Fprintf(w, "http.HandleFunc")
12     })
13
14     http.Handle("/handle", &myHandler{})
15
16     http.ListenAndServe(":8080", nil)
17 }
18
19 type myHandler struct{}
20
21 func (this *myHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
22     fmt.Fprintf(w, "http.Handle")
23 }

2). implement

a) top layer:

// Objects implementing the Handler interface can be
// registered to serve a particular path or subtree
// in the HTTP server.
//
// ServeHTTP should write reply headers and data to the ResponseWriter
// and then return.  Returning signals that the request is finished
// and that the HTTP server can move on to the next request on
// the connection.
type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers.  If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler object that calls f.
type HandlerFunc func(ResponseWriter, *Request)

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

// Handle registers the handler for the given pattern
// in the DefaultServeMux.
// The documentation for ServeMux explains how patterns are matched.
func Handle(pattern string, handler Handler) { DefaultServeMux.Handle(pattern, handler) }

// HandleFunc registers the handler function for the given pattern
// in the DefaultServeMux.
// The documentation for ServeMux explains how patterns are matched.
func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
    DefaultServeMux.HandleFunc(pattern, handler)
}

Now we know that both of http.HandleFunc and http.Handle invoke function of DefaultServeMux.

b) DefaultServeMux

// NewServeMux allocates and returns a new ServeMux.
func NewServeMux() *ServeMux { return &ServeMux{m: make(map[string]muxEntry)} }

// DefaultServeMux is the default ServeMux used by Serve.
var DefaultServeMux = NewServeMux()

// ServeMux is an HTTP request multiplexer.
// It matches the URL of each incoming request against a list of registered
// patterns and calls the handler for the pattern that
// most closely matches the URL.
//
type ServeMux struct {
    mu    sync.RWMutex
    m     map[string]muxEntry
    hosts bool // whether any patterns contain hostnames
}

type muxEntry struct {
    explicit bool
    h        Handler
    pattern  string
}

// HandleFunc registers the handler function for the given pattern.
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
    mux.Handle(pattern, HandlerFunc(handler))
}

// Handle registers the handler for the given pattern.
// If a handler already exists for pattern, Handle panics.
func (mux *ServeMux) Handle(pattern string, handler Handler) {
    mux.mu.Lock()
    defer mux.mu.Unlock()

    if pattern == "" {
        panic("http: invalid pattern " + pattern)
    }
    if handler == nil {
        panic("http: nil handler")
    }
    if mux.m[pattern].explicit {
        panic("http: multiple registrations for " + pattern)
    }

    mux.m[pattern] = muxEntry{explicit: true, h: handler, pattern: pattern}

    if pattern[0] != ‘/‘ {
        mux.hosts = true
    }

    // Helpful behavior:
    // If pattern is /tree/, insert an implicit permanent redirect for /tree.
    // It can be overridden by an explicit registration.
    n := len(pattern)
    if n > 0 && pattern[n-1] == ‘/‘ && !mux.m[pattern[0:n-1]].explicit {
        // If pattern contains a host name, strip it and use remaining
        // path for redirect.
        path := pattern
        if pattern[0] != ‘/‘ {
            // In pattern, at least the last character is a ‘/‘, so
            // strings.Index can‘t be -1.
            path = pattern[strings.Index(pattern, "/"):]
        }
        mux.m[pattern[0:n-1]] = muxEntry{h: RedirectHandler(path, StatusMovedPermanently), pattern: pattern}
    }
}

2. rounter in beego