golang http 服务器的接口梳理

golang http 服务器的接口梳理

Golang构建HTTP服务（二）--- Handler，ServeMux与中间件

Hanlde和HandleFunc以及Handler, HandlerFunc

func Handle(pattern string, handler Handler)
// Handle 函数将pattern和对应的handler注册进DefaultServeMux
func HandleFunc(pattern string, handler func(ResponseWriter, *Request))
// HandleFunc registers the handler function for the given pattern in the DefaultServeMux
// Handler
//
type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}
// HandlerFunc能够将一个普通的处理函数转化为Handler
type HandlerFunc func(ResponseWriter, *Request)

HandleFunc仅接受一个func为参数，相对于简洁些。Handle则需要传入一个带有ServeHTTP的结构体，因此控制逻辑可以灵活些。

Handle的例子

package main

import (
    "fmt"
    "log"
    "net/http"
    "sync"
)

type countHandler struct {
    mu  sync.Mutex // guards n
    n   int
}

func (h *countHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    h.mu.Lock()
    defer h.mu.Unlock()
    h.n++
    fmt.Fprintf(w, "count is %d\n", h.n)
}

func main() {
    http.Handle("/count", new(countHandler))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

HandleFunc的例子

h1 := func(w http.ResponseWriter, _ *http.Request) {
    io.WriteString(w, "Hello from a HandleFunc #1!\n")
}
h2 := func(w http.ResponseWriter, _ *http.Request) {
    io.WriteString(w, "Hello from a HandleFunc #2!\n")
}

http.HandleFunc("/", h1)
http.HandleFunc("/endpoint", h2)

log.Fatal(http.ListenAndServe(":8080", nil))

##### ListenAndServe
```
// 监听TCP然后调用handler对应的Serve去处理请求。handler默认为nil，则使用DefaultServeMux
func ListenAndServe(addr string, handler Handler) error
```
##### ServeMux
路由调度器，根据请求url调用handler去处理。实现了Handle，HandleFunc方法。
ServeMux实现了ServeHTTP因此也是一个Handler接口
```
// 新建
func NewServeMux() *ServeMux
// 方法
func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request)
func (mux *ServeMux) Handle(pattern string, handler Handler)
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request))
func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string)
//
mux := http.NewServeMux()
mux.Handle("/api/", apiHandler{})
mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
// The "/" pattern matches everything, so we need to check
// that we're at the root here.
if req.URL.Path != "/" {
http.NotFound(w, req)
return
}
fmt.Fprintf(w, "Welcome to the home page!")
})
```
##### Server 类型
```
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
// contains filtered or unexported fields
}
// 方法
func (srv *Server) Close() error
func (srv *Server) ListenAndServe() error
func (srv *Server) ListenAndServeTLS(certFile, keyFile string) error
func (srv *Server) RegisterOnShutdown(f func())
func (srv *Server) Serve(l net.Listener) error
func (srv *Server) ServeTLS(l net.Listener, certFile, keyFile string) error
func (srv *Server) SetKeepAlivesEnabled(v bool)
func (srv *Server) Shutdown(ctx context.Context) error
```
可以通过Server类型来改变默认的Server配置，如改变监听端口等。
```
func main(){
http.HandleFunc("/", index)

server := &http.Server{
    Addr: ":8000",
    ReadTimeout: 60 * time.Second,
    WriteTimeout: 60 * time.Second,
}
server.ListenAndServe()

}

// 自定义的serverMux对象也可以传到server对象中。

func main() {

mux := http.NewServeMux()
mux.HandleFunc("/", index)

server := &http.Server{
    Addr: ":8000",
    ReadTimeout: 60 * time.Second,
    WriteTimeout: 60 * time.Second,
    Handler: mux,
}
server.ListenAndServe()

}