关于golang:Go-每日一库之-gorillahandlers

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简介

上一篇文章中,咱们介绍了 gorilla web 开发工具包中的路由治理库gorilla/mux,在文章最初咱们介绍了如何应用中间件解决通用的逻辑。在日常 Go Web 开发中,开发者遇到了很多雷同的中间件需要,gorilla/handlers(后文简称为handlers)收集了一些比拟罕用的中间件。一起来看看吧~

对于中间件,后面几篇文章曾经介绍的很多了。这里就不赘述了。handlers库提供的中间件可用于规范库 net/http 和所有反对 http.Handler 接口的框架。因为 gorilla/mux 也反对 http.Handler 接口,所以也能够与 handlers 库联合应用。这就是兼容规范的益处

我的项目初始化 & 装置

本文代码应用 Go Modules。

创立目录并初始化:

$ mkdir gorilla/handlers && cd gorilla/handlers
$ go mod init github.com/darjun/go-daily-lib/gorilla/handlers

装置 gorilla/handlers 库:

$ go get -u github.com/gorilla/handlers

上面顺次介绍各个中间件和相应的源码。

日志

handlers提供了两个日志中间件:

  • LoggingHandler:以 Apache 的 Common Log Format 日志格局记录 HTTP 申请日志;
  • CombinedLoggingHandler:以 Apache 的 Combined Log Format 日志格局记录 HTTP 申请日志,Apache 和 Nginx 默认都应用这种日志格局。

两种日志格局差异很小,Common Log Format格局如下:

%h %l %u %t "%r" %>s %b

各个批示符含意如下:

  • %h:客户端的 IP 地址或主机名;
  • %lRFC 1413定义的客户端标识,由客户端机器上的 identd 程序生成。如果不存在,则该字段为-
  • %u:已验证的用户名。如果不存在,该字段为-
  • %t:工夫,格局为day/month/year:hour:minute:second zone,其中:

    • day:2 位数字;
    • month:月份缩写,3 个字母,如Jan
    • year:4 位数字;
    • hour:2 位数字;
    • minute:2 位数字;
    • second:2 位数字;
    • zone+- 后跟 4 位数字;
    • 例如:21/Jul/2021:06:27:33 +0800
  • %r:蕴含 HTTP 申请行信息,例GET /index.html HTTP/1.1
  • %>s:服务器发送给客户端的状态码,例如200
  • %b:响应长度(字节数)。

Combined Log Format格局如下:

%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-Agent}i"

可见相比 Common Log Format 只是多了:

  • %{Referer}i:HTTP 首部中的 Referer 信息;
  • %{User-Agent}i:HTTP 首部中的 User-Agent 信息。

对中间件,咱们能够让它作用于全局,即全副处理器,也能够让它只对某些处理器失效。如果要对所有处理器失效,能够调用 Use() 办法。如果只须要作用于特定的处理器,在注册时用中间件将处理器包装一层:

func index(w http.ResponseWriter, r *http.Request) {fmt.Fprintln(w, "Hello World")
}

type greeting string

func (g greeting) ServeHTTP(w http.ResponseWriter, r *http.Request) {fmt.Fprintf(w, "Welcome, %s", g)
}

func main() {r := mux.NewRouter()
  r.Handle("/", handlers.LoggingHandler(os.Stdout, http.HandlerFunc(index)))
  r.Handle("/greeting", handlers.CombinedLoggingHandler(os.Stdout, greeting("dj")))

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

下面代码中 LoggingHandler 只作用于处理函数 indexCombinedLoggingHandler 只作用于处理器greeting("dj")

运行代码,通过浏览器拜访 localhost:8080localhost:8080/greeting

::1 - - [21/Jul/2021:06:39:45 +0800] "GET / HTTP/1.1" 200 12
::1 - - [21/Jul/2021:06:39:54 +0800] "GET /greeting HTTP/1.1" 200 11 """Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.164 Safari/537.36"

对照后面剖析的批示符,很容易看出各个局部。

因为 *mux.RouterUse()办法承受类型为 MiddlewareFunc 的中间件:

type MiddlewareFunc func(http.Handler) http.Handler

handlers.LoggingHandler/CombinedLoggingHandler 并不满足,所以还须要包装一层能力传给 Use() 办法:

func Logging(handler http.Handler) http.Handler {return handlers.CombinedLoggingHandler(os.Stdout, handler)
}

func main() {r := mux.NewRouter()
  r.Use(Logging)
  r.HandleFunc("/", index)
  r.Handle("/greeting/", greeting("dj"))

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

另外 handlers 还提供了CustomLoggingHandler,咱们能够利用它定义本人的日志中间件:

func CustomLoggingHandler(out io.Writer, h http.Handler, f LogFormatter) http.Handler

最要害的 LogFormatter 类型定义:

type LogFormatterParams struct {
  Request    *http.Request
  URL        url.URL
  TimeStamp  time.Time
  StatusCode int
  Size       int
}

type LogFormatter func(writer io.Writer, params LogFormatterParams)

咱们实现一个简略的LogFormatter,记录时间 + 申请行 + 响应码:

func myLogFormatter(writer io.Writer, params handlers.LogFormatterParams) {
  var buf bytes.Buffer
  buf.WriteString(time.Now().Format("2006-01-02 15:04:05 -0700"))
  buf.WriteString(fmt.Sprintf(` "%s %s %s" `, params.Request.Method, params.URL.Path, params.Request.Proto))
  buf.WriteString(strconv.Itoa(params.StatusCode))
  buf.WriteByte('\n')

  writer.Write(buf.Bytes())
}

func Logging(handler http.Handler) http.Handler {return handlers.CustomLoggingHandler(os.Stdout, handler, myLogFormatter)
}

应用:

func main() {r := mux.NewRouter()
  r.Use(Logging)
  r.HandleFunc("/", index)
  r.Handle("/greeting/", greeting("dj"))

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

当初记录的日志是上面这种格局:

2021-07-21 07:03:18 +0800 "GET /greeting/ HTTP/1.1" 200

翻看源码,咱们能够发现 LoggingHandler/CombinedLoggingHandler/CustomLoggingHandler 都是基于底层的 loggingHandler 实现的,不同的是 LoggingHandler 应用了预约义的 writeLog 作为 LogFormatterCombinedLoggingHandler 应用了预约义的 writeCombinedLog 作为 LogFormatter,而CustomLoggingHandler 应用咱们本人定义的LogFormatter

func CombinedLoggingHandler(out io.Writer, h http.Handler) http.Handler {return loggingHandler{out, h, writeCombinedLog}
}

func LoggingHandler(out io.Writer, h http.Handler) http.Handler {return loggingHandler{out, h, writeLog}
}

func CustomLoggingHandler(out io.Writer, h http.Handler, f LogFormatter) http.Handler {return loggingHandler{out, h, f}
}

预约义的 writeLog/writeCombinedLog 实现如下:

func writeLog(writer io.Writer, params LogFormatterParams) {buf := buildCommonLogLine(params.Request, params.URL, params.TimeStamp, params.StatusCode, params.Size)
  buf = append(buf, '\n')
  writer.Write(buf)
}

func writeCombinedLog(writer io.Writer, params LogFormatterParams) {buf := buildCommonLogLine(params.Request, params.URL, params.TimeStamp, params.StatusCode, params.Size)
  buf = append(buf, ` "`...)
  buf = appendQuoted(buf, params.Request.Referer())
  buf = append(buf, `" "`...)
  buf = appendQuoted(buf, params.Request.UserAgent())
  buf = append(buf, '"','\n')
  writer.Write(buf)
}

它们都是基于 buildCommonLogLine 结构根本信息,writeCombinedLog还别离调用 http.Request.Referer()http.Request.UserAgent获取了 RefererUser-Agent信息。

loggingHandler定义如下:

type loggingHandler struct {
  writer    io.Writer
  handler   http.Handler
  formatter LogFormatter
}

loggingHandler实现有一个比拟奇妙的中央:为了记录响应码和响应大小,定义了一个类型 responseLogger 包装原来的http.ResponseWriter,在写入时记录信息:

type responseLogger struct {
  w      http.ResponseWriter
  status int
  size   int
}

func (l *responseLogger) Write(b []byte) (int, error) {size, err := l.w.Write(b)
  l.size += size
  return size, err
}

func (l *responseLogger) WriteHeader(s int) {l.w.WriteHeader(s)
  l.status = s
}

func (l *responseLogger) Status() int {return l.status}

func (l *responseLogger) Size() int {return l.size}

loggingHandler的要害办法ServeHTTP()

func (h loggingHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {t := time.Now()
  logger, w := makeLogger(w)
  url := *req.URL

  h.handler.ServeHTTP(w, req)
  if req.MultipartForm != nil {req.MultipartForm.RemoveAll()
  }

  params := LogFormatterParams{
    Request:    req,
    URL:        url,
    TimeStamp:  t,
    StatusCode: logger.Status(),
    Size:       logger.Size(),}

  h.formatter(h.writer, params)
}

结构 LogFormatterParams 对象,调用对应的 LogFormatter 函数。

压缩

如果客户端申请中有 Accept-Encoding 首部,服务器能够应用该首部批示的算法将响应压缩,以节俭网络流量。handlers.CompressHandler中间件启用压缩性能。还有一个 CompressHandlerLevel 能够指定压缩级别。实际上 CompressHandler 就是应用 gzip.DefaultCompression 调用的CompressHandlerLevel

func CompressHandler(h http.Handler) http.Handler {return CompressHandlerLevel(h, gzip.DefaultCompression)
}

看代码:

func index(w http.ResponseWriter, r *http.Request) {fmt.Fprintln(w, "Hello World")
}

type greeting string

func (g greeting) ServeHTTP(w http.ResponseWriter, r *http.Request) {fmt.Fprintf(w, "Welcome, %s", g)
}

func main() {r := mux.NewRouter()
  r.Use(handlers.CompressHandler)
  r.HandleFunc("/", index)
  r.Handle("/greeting/", greeting("dj"))

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

运行,申请localhost:8080,通过 Chrome 开发者工具的 Network 页签能够看到响应采纳了 gzip 压缩:

疏忽一些细节解决,CompressHandlerLevel函数代码如下:

func CompressHandlerLevel(h http.Handler, level int) http.Handler {
  const (
    gzipEncoding  = "gzip"
    flateEncoding = "deflate"
  )

  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    var encoding string
    for _, curEnc := range strings.Split(r.Header.Get(acceptEncoding), ",") {curEnc = strings.TrimSpace(curEnc)
      if curEnc == gzipEncoding || curEnc == flateEncoding {
        encoding = curEnc
        break
      }
    }

    if encoding == "" {h.ServeHTTP(w, r)
      return
    }

    if r.Header.Get("Upgrade") != "" {h.ServeHTTP(w, r)
      return
    }

    var encWriter io.WriteCloser
    if encoding == gzipEncoding {encWriter, _ = gzip.NewWriterLevel(w, level)
    } else if encoding == flateEncoding {encWriter, _ = flate.NewWriter(w, level)
    }
    defer encWriter.Close()

    w.Header().Set("Content-Encoding", encoding)
    r.Header.Del(acceptEncoding)

    cw := &compressResponseWriter{
      w:          w,
      compressor: encWriter,
    }

    w = httpsnoop.Wrap(w, httpsnoop.Hooks{Write: func(httpsnoop.WriteFunc) httpsnoop.WriteFunc {return cw.Write},
      WriteHeader: func(httpsnoop.WriteHeaderFunc) httpsnoop.WriteHeaderFunc {return cw.WriteHeader},
      Flush: func(httpsnoop.FlushFunc) httpsnoop.FlushFunc {return cw.Flush},
      ReadFrom: func(rff httpsnoop.ReadFromFunc) httpsnoop.ReadFromFunc {return cw.ReadFrom},
    })

    h.ServeHTTP(w, r)
  })
}

从申请 Accept-Encoding 首部中获取客户端批示的压缩算法。如果客户端未指定,或申请首部中有 Upgrade,则不压缩。反之,则压缩。依据辨认的压缩算法,创立对应gzipflateio.Writer 实现对象。

与后面的日志中间件一样,为了压缩写入的内容,新增类型 compressResponseWriter 封装 http.ResponseWriter,重写Write() 办法,将写入的字节流传入后面创立的 io.Writer 实现压缩:

type compressResponseWriter struct {
  compressor io.Writer
  w          http.ResponseWriter
}

func (cw *compressResponseWriter) Write(b []byte) (int, error) {h := cw.w.Header()
  if h.Get("Content-Type") == "" {h.Set("Content-Type", http.DetectContentType(b))
  }
  h.Del("Content-Length")

  return cw.compressor.Write(b)
}

内容类型

咱们能够通过 handler.ContentTypeHandler 指定申请的 Content-Type 必须在咱们给出的类型中,只对 POST/PUT/PATCH 办法失效。例如咱们限度登录申请必须通过 application/x-www-form-urlencoded 的模式发送:

func main() {r := mux.NewRouter()
  r.HandleFunc("/", index)
  r.Methods("GET").Path("/login").HandlerFunc(login)
  r.Methods("POST").Path("/login").
    Handler(handlers.ContentTypeHandler(http.HandlerFunc(dologin), "application/x-www-form-urlencoded"))

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

这样,只有申请 /loginContent-Type不是 application/x-www-form-urlencoded 就会返回 415 谬误。咱们能够成心写错,再申请看看体现:

Unsupported content type "application/x-www-form-urlencoded"; expected one of ["application/x-www-from-urlencoded"]

ContentTypeHandler的实现非常简单:

func ContentTypeHandler(h http.Handler, contentTypes ...string) http.Handler {return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {if !(r.Method == "PUT" || r.Method == "POST" || r.Method == "PATCH") {h.ServeHTTP(w, r)
      return
    }

    for _, ct := range contentTypes {if isContentType(r.Header, ct) {h.ServeHTTP(w, r)
        return
      }
    }
    http.Error(w, fmt.Sprintf("Unsupported content type %q; expected one of %q", r.Header.Get("Content-Type"), contentTypes), http.StatusUnsupportedMediaType)
  })
}

就是读取 Content-Type 首部,判断是否在咱们指定的类型中。

办法处理器

在下面的例子中,咱们注册门路 /loginGETPOST 办法解决采纳 r.Methods("GET").Path("/login").HandlerFunc(login) 这种简短的写法。handlers.MethodHandler能够简化这种写法:

func main() {r := mux.NewRouter()
  r.HandleFunc("/", index)
  r.Handle("/login", handlers.MethodHandler{"GET":  http.HandlerFunc(login),
    "POST": http.HandlerFunc(dologin),
  })

  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

MethodHandler底层是一个 map[string]http.Handler 类型,它的 ServeHTTP() 办法依据申请的 Method 调用不同的解决:

type MethodHandler map[string]http.Handler

func (h MethodHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {if handler, ok := h[req.Method]; ok {handler.ServeHTTP(w, req)
  } else {allow := []string{}
    for k := range h {allow = append(allow, k)
    }
    sort.Strings(allow)
    w.Header().Set("Allow", strings.Join(allow, ","))
    if req.Method == "OPTIONS" {w.WriteHeader(http.StatusOK)
    } else {http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
    }
  }
}

办法如果未注册,则返回 405 Method Not Allowed。有一个办法除外,OPTIONS。该办法通过Allow 首部返回反对哪些办法。

重定向

handlers.CanonicalHost能够将申请重定向到指定的域名,同时指定重定向响应码。在同一个服务器对应多个域名时比拟有用:

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

func main() {r := mux.NewRouter()
  r.Use(handlers.CanonicalHost("http://www.gorillatoolkit.org", 302))
  r.HandleFunc("/", index)
  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

下面将所有申请以 302 重定向到http://www.gorillatoolkit.org

CanonicalHost的实现也很简略:

func CanonicalHost(domain string, code int) func(h http.Handler) http.Handler {fn := func(h http.Handler) http.Handler {return canonical{h, domain, code}
  }

  return fn
}

要害类型canonical

type canonical struct {
  h      http.Handler
  domain string
  code   int
}

外围办法:

func (c canonical) ServeHTTP(w http.ResponseWriter, r *http.Request) {dest, err := url.Parse(c.domain)
  if err != nil {c.h.ServeHTTP(w, r)
    return
  }

  if dest.Scheme == ""|| dest.Host =="" {c.h.ServeHTTP(w, r)
    return
  }

  if !strings.EqualFold(cleanHost(r.Host), dest.Host) {
    dest := dest.Scheme + "://" + dest.Host + r.URL.Path
    if r.URL.RawQuery != "" {dest += "?" + r.URL.RawQuery}
    http.Redirect(w, r, dest, c.code)
    return
  }

  c.h.ServeHTTP(w, r)
}

由源码可知,域名不非法或未指定协定(Scheme)或域名(Host)的申请下不转发。

Recovery

之前咱们本人实现了 PanicRecover 中间件,防止申请解决时 panic。handlers提供了一个 RecoveryHandler 能够间接应用:

func PANIC(w http.ResponseWriter, r *http.Request) {panic(errors.New("unexpected error"))
}

func main() {r := mux.NewRouter()
  r.Use(handlers.RecoveryHandler(handlers.PrintRecoveryStack(true)))
  r.HandleFunc("/", PANIC)
  http.Handle("/", r)
  log.Fatal(http.ListenAndServe(":8080", nil))
}

选项 PrintRecoveryStack 示意 panic 时输入堆栈信息。

RecoveryHandler的实现与之前咱们本人编写的根本一样:

type recoveryHandler struct {
  handler    http.Handler
  logger     RecoveryHandlerLogger
  printStack bool
}

func (h recoveryHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {defer func() {if err := recover(); err != nil {w.WriteHeader(http.StatusInternalServerError)
      h.log(err)
    }
  }()

  h.handler.ServeHTTP(w, req)
}

总结

GitHub 上有很多开源的 Go Web 中间件实现,能够间接拿来应用,防止反复造轮子。handlers很轻量,容易与规范库 net/http 和 gorilla 路由库 mux 联合应用。

大家如果发现好玩、好用的 Go 语言库,欢送到 Go 每日一库 GitHub 上提交 issue😄

参考

  1. gorilla/handlers GitHub:github.com/gorilla/handlers
  2. Go 每日一库 GitHub:https://github.com/darjun/go-daily-lib

我的博客:https://darjun.github.io

欢送关注我的微信公众号【GoUpUp】,独特学习,一起提高~

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