专栏首页Golang语言社区go http 服务器编程(2)

go http 服务器编程(2)

match 会遍历路由信息字典,找到所有匹配该路径最长的那个。路由部分的代码解释就到这里了,最后回答上面的一个问题:http.HandleFuncServeMux.HandlerFunc 是什么关系?

// 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)
}

原来是直接通过 DefaultServeMux 调用对应的方法,到这里上面的一切都串起来了!

Request

最后一部分,要讲讲 Handler 函数接受的两个参数:http.Requesthttp.ResponseWriter

Request 就是封装好的客户端请求,包括 URL,method,header 等等所有信息,以及一些方便使用的方法:

// A Request represents an HTTP request received by a server
// or to be sent by a client.
//
// The field semantics differ slightly between client and server
// usage. In addition to the notes on the fields below, see the
// documentation for Request.Write and RoundTripper.
type Request struct {
	// Method specifies the HTTP method (GET, POST, PUT, etc.).
	// For client requests an empty string means GET.
	Method string

	// URL specifies either the URI being requested (for server
	// requests) or the URL to access (for client requests).
	//
	// For server requests the URL is parsed from the URI
	// supplied on the Request-Line as stored in RequestURI.  For
	// most requests, fields other than Path and RawQuery will be
	// empty. (See RFC 2616, Section 5.1.2)
	//
	// For client requests, the URL's Host specifies the server to
	// connect to, while the Request's Host field optionally
	// specifies the Host header value to send in the HTTP
	// request.
	URL *url.URL

	// The protocol version for incoming requests.
	// Client requests always use HTTP/1.1.
	Proto      string // "HTTP/1.0"
	ProtoMajor int    // 1
	ProtoMinor int    // 0

	// A header maps request lines to their values.
	// If the header says
	//
	//	accept-encoding: gzip, deflate
	//	Accept-Language: en-us
	//	Connection: keep-alive
	//
	// then
	//
	//	Header = map[string][]string{
	//		"Accept-Encoding": {"gzip, deflate"},
	//		"Accept-Language": {"en-us"},
	//		"Connection": {"keep-alive"},
	//	}
	//
	// HTTP defines that header names are case-insensitive.
	// The request parser implements this by canonicalizing the
	// name, making the first character and any characters
	// following a hyphen uppercase and the rest lowercase.
	//
	// For client requests certain headers are automatically
	// added and may override values in Header.
	//
	// See the documentation for the Request.Write method.
	Header Header

	// Body is the request's body.
	//
	// For client requests a nil body means the request has no
	// body, such as a GET request. The HTTP Client's Transport
	// is responsible for calling the Close method.
	//
	// For server requests the Request Body is always non-nil
	// but will return EOF immediately when no body is present.
	// The Server will close the request body. The ServeHTTP
	// Handler does not need to.
	Body io.ReadCloser

	// ContentLength records the length of the associated content.
	// The value -1 indicates that the length is unknown.
	// Values >= 0 indicate that the given number of bytes may
	// be read from Body.
	// For client requests, a value of 0 means unknown if Body is not nil.
	ContentLength int64

	// TransferEncoding lists the transfer encodings from outermost to
	// innermost. An empty list denotes the "identity" encoding.
	// TransferEncoding can usually be ignored; chunked encoding is
	// automatically added and removed as necessary when sending and
	// receiving requests.
	TransferEncoding []string

	// Close indicates whether to close the connection after
	// replying to this request (for servers) or after sending
	// the request (for clients).
	Close bool

	// For server requests Host specifies the host on which the
	// URL is sought. Per RFC 2616, this is either the value of
	// the "Host" header or the host name given in the URL itself.
	// It may be of the form "host:port".
	//
	// For client requests Host optionally overrides the Host
	// header to send. If empty, the Request.Write method uses
	// the value of URL.Host.
	Host string

	// Form contains the parsed form data, including both the URL
	// field's query parameters and the POST or PUT form data.
	// This field is only available after ParseForm is called.
	// The HTTP client ignores Form and uses Body instead.
	Form url.Values

	// PostForm contains the parsed form data from POST or PUT
	// body parameters.
	// This field is only available after ParseForm is called.
	// The HTTP client ignores PostForm and uses Body instead.
	PostForm url.Values

	// MultipartForm is the parsed multipart form, including file uploads.
	// This field is only available after ParseMultipartForm is called.
	// The HTTP client ignores MultipartForm and uses Body instead.
	MultipartForm *multipart.Form

	...

	// RemoteAddr allows HTTP servers and other software to record
	// the network address that sent the request, usually for
	// logging. This field is not filled in by ReadRequest and
	// has no defined format. The HTTP server in this package
	// sets RemoteAddr to an "IP:port" address before invoking a
	// handler.
	// This field is ignored by the HTTP client.
	RemoteAddr string
    ...
}

Handler 需要知道关于请求的任何信息,都要从这个对象中获取,一般不会直接修改这个对象(除非你非常清楚自己在做什么)!

ResponseWriter

ResponseWriter 是一个接口,定义了三个方法:

  • Header():返回一个 Header 对象,可以通过它的 Set() 方法设置头部,注意最终返回的头部信息可能和你写进去的不完全相同,因为后续处理还可能修改头部的值(比如设置Content-LengthContent-type 等操作)
  • Write(): 写 response 的主体部分,比如 html 或者 json 的内容就是放到这里的
  • WriteHeader():设置 status code,如果没有调用这个函数,默认设置为 http.StatusOK, 就是 200 状态码
// A ResponseWriter interface is used by an HTTP handler to
// construct an HTTP response.
type ResponseWriter interface {
	// Header returns the header map that will be sent by WriteHeader.
	// Changing the header after a call to WriteHeader (or Write) has
	// no effect.
	Header() Header

	// Write writes the data to the connection as part of an HTTP reply.
	// If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK)
	// before writing the data.  If the Header does not contain a
	// Content-Type line, Write adds a Content-Type set to the result of passing
	// the initial 512 bytes of written data to DetectContentType.
	Write([]byte) (int, error)

	// WriteHeader sends an HTTP response header with status code.
	// If WriteHeader is not called explicitly, the first call to Write
	// will trigger an implicit WriteHeader(http.StatusOK).
	// Thus explicit calls to WriteHeader are mainly used to
	// send error codes.
	WriteHeader(int)
}

实际上传递给 Handler 的对象是:

// A response represents the server side of an HTTP response.
type response struct {
	conn          *conn
	req           *Request // request for this response
	wroteHeader   bool     // reply header has been (logically) written
	wroteContinue bool     // 100 Continue response was written

	w  *bufio.Writer // buffers output in chunks to chunkWriter
	cw chunkWriter
	sw *switchWriter // of the bufio.Writer, for return to putBufioWriter

	// handlerHeader is the Header that Handlers get access to,
	// which may be retained and mutated even after WriteHeader.
	// handlerHeader is copied into cw.header at WriteHeader
	// time, and privately mutated thereafter.
	handlerHeader Header
	...
	status        int   // status code passed to WriteHeader
    ...
}

它当然实现了上面提到的三个方法,具体代码就不放到这里了,感兴趣的可以自己去看。

6. 扩展

虽然 net/http 提供的各种功能已经满足基本需求了,但是很多时候还不够方便,比如:

  • 不支持 URL 匹配,所有的路径必须完全匹配,不能捕获 URL 中的变量,不够灵活
  • 不支持 HTTP 方法匹配
  • 不支持扩展和嵌套,URL 处理都在都一个 ServeMux 变量中

虽然这些都可以自己手动去码,但实在很不方便。这部分看看有哪些三方的包,都提供了哪些额外的功能。

alice

alice 的功能很简单——把多个 handler 串联起来,有请求过来的时候,逐个通过这个 handler 进行处理。

alice.New(Middleware1, Middleware2, Middleware3).Then(App)

Gorilla Mux

Gorilla 提供了很多网络有关的组件, Mux 就是其中一个,负责 HTTP 的路由功能。这个组件弥补了上面提到的 ServeMux 的一些缺陷,支持的功能有:

  • 更多的匹配类型:HTTP 方法、query 字段、URL host 等
  • 支持正则表达式作为 URL path 的一部分,也支持变量提取功能
  • 支持子路由,也就是路由的嵌套,SubRouter 可以实现路由信息的传递
  • 并且和 ServeMux 完全兼容
r := mux.NewRouter()
r.HandleFunc("/products/{key}", ProductHandler)
r.HandleFunc("/articles/{category}/", ArticlesCategoryHandler)
r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)

httprouter

httprouter 和 mux 一样,也是扩展了自带 ServeMux 功能的路由库。它的主要特点是速度快、内存使用少、可扩展性高(使用 radix tree 数据结构进行路由匹配,路由项很多的时候速度也很快)。

package main

import (
    "fmt"
    "github.com/julienschmidt/httprouter"
    "net/http"
    "log"
)

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "hello, %s!\n", ps.ByName("name"))
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/hello/:name", Hello)

    log.Fatal(http.ListenAndServe(":8080", router))
}

negroni

http middleware 库,支持嵌套的中间件,能够和其他路由库兼容。同时它也自带了不少 middleware 可以使用,比如RecoveryLoggerStatic

router := mux.NewRouter()
router.HandleFunc("/", HomeHandler)

n := negroni.New(Middleware1, Middleware2)
// Or use a middleware with the Use() function
n.Use(Middleware3)
// router goes last
n.UseHandler(router)

http.ListenAndServe(":3001", n)

7. 参考

这篇文章参考了以下资料:

本文来自:开源中国博客

感谢作者:柠檬酷

查看原文:go http 服务器编程

本文分享自微信公众号 - Golang语言社区(Golangweb)

原文出处及转载信息见文内详细说明,如有侵权,请联系 yunjia_community@tencent.com 删除。

原始发表时间:2016-11-01

本文参与腾讯云自媒体分享计划,欢迎正在阅读的你也加入,一起分享。

我来说两句

0 条评论
登录 后参与评论

相关文章

  • Methods in Go

    Go supports some object-orient programming features. Method is one of these feat...

    李海彬
  • 阅读源代码的姿势:以 go-restful 为例

    一般初学者确定一个方向,比如web 后端、前端等,会选择一门编程语言深入下去,比如后端java、python、go等。通过项目不断练习编程语言和编程思维,知道如...

    李海彬
  • Knapsack problem algorithms for my real-life carry-on knapsack

    I'm a nomad and live out of one carry-on bag. This means that the total weight o...

    李海彬
  • Code forces 719A Vitya in the Countryside

    A. Vitya in the Countryside time limit per test:1 second memory limit per test:2...

    Angel_Kitty
  • 解决:TF30170: Microsoft.ProjectCreationWizard.WorkItemTracking

    Error TF30170: The plugin Microsoft.ProjectCreationWizard.WorkItemTracking fail...

    阿新
  • SAP OData性能分析工具

    As mentioned by title, this blog does not introduce the OData trace functionalit...

    Jerry Wang
  • CC1310空中升级笔记03 CC1350_BLE_OAD_Project0

    如果打不开这个TI的链接,我上传了整个网页,http://download.csdn.net/detail/iotisan/9750301。

    twowinter
  • 什么是SAP物料主数据里的Batch

    Materials are produced and theoretically have the same properties. Nevertheless ...

    Jerry Wang
  • 如何启用SAP Business by design里的Correction Invoice功能

    Subject: [Tip] How to enable the function Correction Invoice for customer invoic...

    Jerry Wang
  • 循环热管的动态状态空间建模与基于模型的控制设计(CS SY)

    对于航空航天、汽车或服务器系统中电子元件的热控制,散热器通常远离热源。因此,热传导系统是有效冷却电子元件所必需的。循环热管(LHPs)就是这样的传热系统,它利用...

    用户6853689

扫码关注云+社区

领取腾讯云代金券