一文带你吃透Golang中net/http标准库服务端

http.HandleFunc("/hello", func(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "xiaoxu code")
})
http.ListenAndServe(":8080", nil)

resp, err := http.Get("http://example.com/")
if err != nil {
    fmt.Println(err)
    return
}
defer resp.Body.Close()
body, _ := ioutil.ReadAll(resp.Body)
fmt.Println(string(body))

type Server struct {
    Addr string
    Handler Handler 
    mu         sync.Mutex
    ReadTimeout time.Duration
    WriteTimeout time.Duration
    IdleTimeout time.Duration
    TLSConfig *tls.Config
    ConnState func(net.Conn, ConnState)
    activeConn map[*conn]struct{}
    doneChan   chan struct{}
    listeners  map[*net.Listener]struct{}
    ...
}

type ServeMux struct {
    mu sync.RWMutex   
    m map[string]muxEntry 
    es []muxEntry    
    hosts bool     
}

var DefaultServeMux = &defaultServeMux
// 默认的ServeMux
var defaultServeMux ServeMux

// HandleFunc注册函数
func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
    DefaultServeMux.HandleFunc(pattern, handler)
}

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

//HandlerFunc为函数类型
type HandlerFunc func(ResponseWriter, *Request)
//实现了Handler接口
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
    f(w, r)
}


func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
    ...
    // handler是真正处理请求的函数
    mux.Handle(pattern, HandlerFunc(handler))
}

func (mux *ServeMux) Handle(pattern string, handler Handler) {
    mux.mu.Lock()
    defer mux.mu.Unlock()
    // 检查路由和处理函数
    ...
    //检查pattern是否存在
    ...
    //如果 mux.m 为nil 进行make初始化 map
    if mux.m == nil {
        mux.m = make(map[string]muxEntry)
    }
    e := muxEntry{h: handler, pattern: pattern}
    //注册好路由都会存放到mux.m里面
    mux.m[pattern] = e
    //patterm以'/'结尾
    if pattern[len(pattern)-1] == '/' {
        mux.es = appendSorted(mux.es, e)
    }

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

func (srv *Server) ListenAndServe() error {
    if srv.shuttingDown() {
        return ErrServerClosed
    }
    addr := srv.Addr
    if addr == "" {
        addr = ":http"
    }
    // 指定网络地址并监听
    ln, err := net.Listen("tcp", addr)
    if err != nil {
        return err
    }
    // 接收处理请求
    return srv.Serve(ln)
}

func (srv *Server) Serve(l net.Listener) error {
    origListener := l
    //内部实现Once是只执行一次动作的对象
    l = &onceCloseListener{Listener: l}
    defer l.Close()
    ...
    ctx := context.WithValue(baseCtx, ServerContextKey, srv)
    for {
        //rw为可理解为tcp连接
        rw, err := l.Accept()
        ...
        connCtx := ctx
        ...
        c := srv.newConn(rw)
        //
        go c.serve(connCtx)
    }
}

type onceCloseListener struct {
    net.Listener
    once     sync.Once
    closeErr error
}

func (c *conn) serve(ctx context.Context) {
    ...
    // 初始化conn的一些参数
    c.remoteAddr = c.rwc.RemoteAddr().String()
    c.r = &connReader{conn: c}
    c.bufr = newBufioReader(c.r)
    c.bufw = newBufioWriterSize(checkConnErrorWriter{c}, 4<<10)
    for {
        // 读取客户端请求
        w, err := c.readRequest(ctx)
        ...
        // 调用ServeHTTP来处理请求
        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传的是nil就执行 DefaultServeMux.ServeHTTP() 方法
    handler.ServeHTTP(rw, req)
}

func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {
    ....
    h, _ := mux.Handler(r)
    // 执行匹配到的路由的ServeHTTP方法
    h.ServeHTTP(w, r)
}

func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string) {
    ...
    //在mux.m和mux.es中
    //根据host/url.path寻找对应的handler
    return mux.handler(host, r.URL.Path)
}

func (mux *ServeMux) match(path string) (h Handler, pattern string) {
    // 是否完全匹配
    v, ok := mux.m[path]
    if ok {
        return v.h, v.pattern
    }
    // mux.es是按pattern从长到短排列
    for _, e := range mux.es {
        if strings.HasPrefix(path, e.pattern) {
            return e.h, e.pattern
        }
    }
    return nil, ""
}

type HandlerFunc func(ResponseWriter, *Request)

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