深入理解Golang之httpserver的实现

package main

import (
 "fmt"
 "net/http"
)

func indexHandler(w http.ResponseWriter, r *http.Request) {
 fmt.Fprintf(w, "hello world")
}

func main() {
 http.HandleFunc("/", indexHandler)
 http.ListenAndServe(":8000", nil)
}

package main

import (
 "fmt"
 "net/http"
)

type indexHandler struct {
 content string
}

func (ih *indexHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 fmt.Fprintf(w, ih.content)
}

func main() {
 http.Handle("/", &indexHandler{content: "hello world!"})
 http.ListenAndServe(":8001", nil)
}

func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
 DefaultServeMux.HandleFunc(pattern, handler)
}

// HandleFunc registers the handler function for the given pattern.
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
 if handler == nil {
  panic("http: nil handler")
 }
 mux.Handle(pattern, HandlerFunc(handler))
}

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

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

mux.Handle(pattern, HandlerFunc(handler))

type HandlerFunc func(ResponseWriter, *Request)

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

type ServeMux struct {
 mu sync.RWMutex
 m  map[string]muxEntry
 es []muxEntry // slice of entries sorted from longest to shortest.
 hosts bool  // whether any patterns contain hostnames
}

type muxEntry struct {
 h  Handler
 pattern string
}

func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {
 if r.RequestURI == "*" {
  if r.ProtoAtLeast(1, 1) {
   w.Header().Set("Connection", "close")
  }
  w.WriteHeader(StatusBadRequest)
  return
 }
 h, _ := mux.Handler(r)
 h.ServeHTTP(w, r)
}

DefaultServeMux.Handle(pattern, handler)

func (mux *ServeMux) Handle(pattern string, handler Handler) {
 mux.mu.Lock()
 defer mux.mu.Unlock()

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

 if mux.m == nil {
  mux.m = make(map[string]muxEntry)
 }
 // 利用当前的路由和handler创建muxEntry对象
 e := muxEntry{h: handler, pattern: pattern}
 // 向ServeMux的map[string]muxEntry增加新的路由匹配规则
 mux.m[pattern] = e
 // 如果路由表达式以'/'结尾，则将对应的muxEntry对象加入到[]muxEntry中，按照路由表达式长度排序
 if pattern[len(pattern)-1] == '/' {
  mux.es = appendSorted(mux.es, e)
 }

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

package main

import (
 "fmt"
 "net/http"
)

func indexHandler(w http.ResponseWriter, r *http.Request) {
 fmt.Fprintf(w, "hello world")
}

func htmlHandler(w http.ResponseWriter, r *http.Request) {
 w.Header().Set("Content-Type", "text/html")
 html := `
 
 
   
     
     
   
   
    
Welcome!
   
 `
 fmt.Fprintf(w, html)
}

func main() {
 mux := http.NewServeMux()
 mux.Handle("/", http.HandlerFunc(indexHandler))
 mux.HandleFunc("/welcome", htmlHandler)
 http.ListenAndServe(":8001", mux)
}

func ListenAndServe(addr string, handler Handler) error {
 server := &Server{Addr: addr, Handler: handler}
 return server.ListenAndServe()
}

func (srv *Server) ListenAndServe() error {
 if srv.shuttingDown() {
  return ErrServerClosed
 }
 addr := srv.Addr
 if addr == "" {
  addr = ":http"
 }
 ln, err := net.Listen("tcp", addr)
 if err != nil {
  return err
 }
 return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})
}

type Server struct {
 Addr string // TCP address to listen on, ":http" if empty
 Handler Handler // handler to invoke, http.DefaultServeMux if nil
 TLSConfig *tls.Config
 ReadTimeout time.Duration
 ReadHeaderTimeout time.Duration
 WriteTimeout time.Duration
 IdleTimeout time.Duration
 MaxHeaderBytes int
 TLSNextProto map[string]func(*Server, *tls.Conn, Handler)
 ConnState func(net.Conn, ConnState)
 ErrorLog *log.Logger

 disableKeepAlives int32  // accessed atomically.
 inShutdown  int32  // accessed atomically (non-zero means we're in Shutdown)
 nextProtoOnce  sync.Once // guards setupHTTP2_* init
 nextProtoErr  error  // result of http2.ConfigureServer if used

 mu   sync.Mutex
 listeners map[*net.Listener]struct{}
 activeConn map[*conn]struct{}
 doneChan chan struct{}
 onShutdown []func()
}

func (srv *Server) Serve(l net.Listener) error {
 ...

 baseCtx := context.Background() // base is always background, per Issue 16220
 ctx := context.WithValue(baseCtx, ServerContextKey, srv)
 for {
  rw, e := l.Accept() // 等待新的连接建立

  ...

  c := srv.newConn(rw)
  c.setState(c.rwc, StateNew) // before Serve can return
  go c.serve(ctx) // 创建新的协程处理请求
 }
}

func (c *conn) serve(ctx context.Context) {

 ...

 for {
  w, err := c.readRequest(ctx)
  if c.r.remain != c.server.initialReadLimitSize() {
   // If we read any bytes off the wire, we're active.
   c.setState(c.rwc, StateActive)
  }

  ...

  // HTTP cannot have multiple simultaneous active requests.[*]
  // Until the server replies to this request, it can't read another,
  // so we might as well run the handler in this goroutine.
  // [*] Not strictly true: HTTP pipelining. We could let them all process
  // in parallel even if their responses need to be serialized.
  // But we're not going to implement HTTP pipelining because it
  // was never deployed in the wild and the answer is HTTP/2.
  serverHandler{c.server}.ServeHTTP(w, w.req)
  w.cancelCtx()
  if c.hijacked() {
   return
  }
  w.finishRequest()
  if !w.shouldReuseConnection() {
   if w.requestBodyLimitHit || w.closedRequestBodyEarly() {
    c.closeWriteAndWait()
   }
   return
  }
  c.setState(c.rwc, StateIdle) // 请求处理结束后，将连接状态置为空闲
  c.curReq.Store((*response)(nil))// 将当前请求置为空

  ...
 }
}

serverHandler{c.server}.ServeHTTP(w, w.req)

type serverHandler struct {
 srv *Server
}

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {
 handler := sh.srv.Handler
 if handler == nil {
  handler = DefaultServeMux
 }
 if req.RequestURI == "*" && req.Method == "OPTIONS" {
  handler = globalOptionsHandler{}
 }
 handler.ServeHTTP(rw, req)
}

// ServeHTTP dispatches the request to the handler whose
// pattern most closely matches the request URL.
func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {
 if r.RequestURI == "*" {
  if r.ProtoAtLeast(1, 1) {
   w.Header().Set("Connection", "close")
  }
  w.WriteHeader(StatusBadRequest)
  return
 }
 h, _ := mux.Handler(r)
 h.ServeHTTP(w, r)
}

func (mux *ServeMux) handler(host, path string) (h Handler, pattern string) {
 mux.mu.RLock()
 defer mux.mu.RUnlock()

 // Host-specific pattern takes precedence over generic ones
 if mux.hosts {
  h, pattern = mux.match(host + path)
 }
 if h == nil {
  h, pattern = mux.match(path)
 }
 if h == nil {
  h, pattern = NotFoundHandler(), ""
 }
 return
}

// Find a handler on a handler map given a path string.
// Most-specific (longest) pattern wins.
func (mux *ServeMux) match(path string) (h Handler, pattern string) {
 // Check for exact match first.
 v, ok := mux.m[path]
 if ok {
  return v.h, v.pattern
 }

 // Check for longest valid match. mux.es contains all patterns
 // that end in / sorted from longest to shortest.
 for _, e := range mux.es {
  if strings.HasPrefix(path, e.pattern) {
   return e.h, e.pattern
  }
 }
 return nil, ""
}