GoLang之标准库net/http包源码

GoLang之标准库net/http包

注：本文是基于Windos系统上Go SDK v1.8进行讲解

1.net/http包介绍

Go语言内置的net/http包提供了HTTP客户端和服务端的实现。
超文本传输协议（HTTP，HyperText Transfer Protocol)是互联网上应用最为广泛的一种网络传输协议，所有的WWW文件都必须遵守这个标准

2.http.ListenAndServe函数

ListenAndServe使用指定的监听地址和处理器启动一个HTTP服务端。处理器参数通常是nil，这表示采用包变量DefaultServeMux作为处理器。

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

3.http.Handle函数

Handle可以向DefaultServeMux添加处理器

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

4.http.HandleFunc函数

HandleFunc函数可以向DefaultServeMux添加处理器。

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

5.gin.const常量

const (
	StatusContinue           = 100 // RFC 7231, 6.2.1
	StatusSwitchingProtocols = 101 // RFC 7231, 6.2.2
	StatusProcessing         = 102 // RFC 2518, 10.1
	StatusEarlyHints         = 103 // RFC 8297

	StatusOK                   = 200 // RFC 7231, 6.3.1
	StatusCreated              = 201 // RFC 7231, 6.3.2
	StatusAccepted             = 202 // RFC 7231, 6.3.3
	StatusNonAuthoritativeInfo = 203 // RFC 7231, 6.3.4
	StatusNoContent            = 204 // RFC 7231, 6.3.5
	StatusResetContent         = 205 // RFC 7231, 6.3.6
	StatusPartialContent       = 206 // RFC 7233, 4.1
	StatusMultiStatus          = 207 // RFC 4918, 11.1
	StatusAlreadyReported      = 208 // RFC 5842, 7.1
	StatusIMUsed               = 226 // RFC 3229, 10.4.1

	StatusMultipleChoices   = 300 // RFC 7231, 6.4.1
	StatusMovedPermanently  = 301 // RFC 7231, 6.4.2
	StatusFound             = 302 // RFC 7231, 6.4.3
	StatusSeeOther          = 303 // RFC 7231, 6.4.4
	StatusNotModified       = 304 // RFC 7232, 4.1
	StatusUseProxy          = 305 // RFC 7231, 6.4.5
	_                       = 306 // RFC 7231, 6.4.6 (Unused)
	StatusTemporaryRedirect = 307 // RFC 7231, 6.4.7
	StatusPermanentRedirect = 308 // RFC 7538, 3

	StatusBadRequest                   = 400 // RFC 7231, 6.5.1
	StatusUnauthorized                 = 401 // RFC 7235, 3.1
	StatusPaymentRequired              = 402 // RFC 7231, 6.5.2
	StatusForbidden                    = 403 // RFC 7231, 6.5.3
	StatusNotFound                     = 404 // RFC 7231, 6.5.4
	StatusMethodNotAllowed             = 405 // RFC 7231, 6.5.5
	StatusNotAcceptable                = 406 // RFC 7231, 6.5.6
	StatusProxyAuthRequired            = 407 // RFC 7235, 3.2
	StatusRequestTimeout               = 408 // RFC 7231, 6.5.7
	StatusConflict                     = 409 // RFC 7231, 6.5.8
	StatusGone                         = 410 // RFC 7231, 6.5.9
	StatusLengthRequired               = 411 // RFC 7231, 6.5.10
	StatusPreconditionFailed           = 412 // RFC 7232, 4.2
	StatusRequestEntityTooLarge        = 413 // RFC 7231, 6.5.11
	StatusRequestURITooLong            = 414 // RFC 7231, 6.5.12
	StatusUnsupportedMediaType         = 415 // RFC 7231, 6.5.13
	StatusRequestedRangeNotSatisfiable = 416 // RFC 7233, 4.4
	StatusExpectationFailed            = 417 // RFC 7231, 6.5.14
	StatusTeapot                       = 418 // RFC 7168, 2.3.3
	StatusMisdirectedRequest           = 421 // RFC 7540, 9.1.2
	StatusUnprocessableEntity          = 422 // RFC 4918, 11.2
	StatusLocked                       = 423 // RFC 4918, 11.3
	StatusFailedDependency             = 424 // RFC 4918, 11.4
	StatusTooEarly                     = 425 // RFC 8470, 5.2.
	StatusUpgradeRequired              = 426 // RFC 7231, 6.5.15
	StatusPreconditionRequired         = 428 // RFC 6585, 3
	StatusTooManyRequests              = 429 // RFC 6585, 4
	StatusRequestHeaderFieldsTooLarge  = 431 // RFC 6585, 5
	StatusUnavailableForLegalReasons   = 451 // RFC 7725, 3

	StatusInternalServerError           = 500 // RFC 7231, 6.6.1
	StatusNotImplemented                = 501 // RFC 7231, 6.6.2
	StatusBadGateway                    = 502 // RFC 7231, 6.6.3
	StatusServiceUnavailable            = 503 // RFC 7231, 6.6.4
	StatusGatewayTimeout                = 504 // RFC 7231, 6.6.5
	StatusHTTPVersionNotSupported       = 505 // RFC 7231, 6.6.6
	StatusVariantAlsoNegotiates         = 506 // RFC 2295, 8.1
	StatusInsufficientStorage           = 507 // RFC 4918, 11.5
	StatusLoopDetected                  = 508 // RFC 5842, 7.2
	StatusNotExtended                   = 510 // RFC 2774, 7
	StatusNetworkAuthenticationRequired = 511 // RFC 6585, 6
)

6.http.Request结构体

//简化版
type Request struct {
	Method string
	URL *url.URL
	Proto      string // "HTTP/1.0"
	ProtoMajor int    // 1
	ProtoMinor int    // 0
	Header Header
	Body io.ReadCloser
	GetBody func() (io.ReadCloser, error)
	ContentLength int64
	TransferEncoding []string
	Close bool
	Host string
	Form url.Values
	PostForm url.Values
	MultipartForm *multipart.Form
	Trailer Header
	RemoteAddr string
	RequestURI string
	TLS *tls.ConnectionState
	Cancel <-chan struct{}
	Response *Response
	ctx context.Context
}

//详细版
// 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.
	//
	// Go's HTTP client does not support sending a request with
	// the CONNECT method. See the documentation on Transport for
	// details.
	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 7230, Section 5.3)
	//
	// 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 server requests.
	//
	// For client requests, these fields are ignored. The HTTP
	// client code always uses either HTTP/1.1 or HTTP/2.
	// See the docs on Transport for details.
	Proto      string // "HTTP/1.0"
	ProtoMajor int    // 1
	ProtoMinor int    // 0

	// Header contains the request header fields either received
	// by the server or to be sent by the client.
	//
	// If a server received a request with header lines,
	//
	//	Host: example.com
	//	accept-encoding: gzip, deflate
	//	Accept-Language: en-us
	//	fOO: Bar
	//	foo: two
	//
	// then
	//
	//	Header = map[string][]string{
	//		"Accept-Encoding": {"gzip, deflate"},
	//		"Accept-Language": {"en-us"},
	//		"Foo": {"Bar", "two"},
	//	}
	//
	// For incoming requests, the Host header is promoted to the
	// Request.Host field and removed from the Header map.
	//
	// HTTP defines that header names are case-insensitive. The
	// request parser implements this by using CanonicalHeaderKey,
	// making the first character and any characters following a
	// hyphen uppercase and the rest lowercase.
	//
	// For client requests, certain headers such as Content-Length
	// and Connection are automatically written when needed and
	// values in Header may be ignored. 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 must allow Read to be called concurrently with Close.
	// In particular, calling Close should unblock a Read waiting
	// for input.
	Body io.ReadCloser

	// GetBody defines an optional func to return a new copy of
	// Body. It is used for client requests when a redirect requires
	// reading the body more than once. Use of GetBody still
	// requires setting Body.
	//
	// For server requests, it is unused.
	GetBody func() (io.ReadCloser, error)

	// 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 with a non-nil Body is
	// also treated as unknown.
	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 this
	// request and reading its response (for clients).
	//
	// For server requests, the HTTP server handles this automatically
	// and this field is not needed by Handlers.
	//
	// For client requests, setting this field prevents re-use of
	// TCP connections between requests to the same hosts, as if
	// Transport.DisableKeepAlives were set.
	Close bool

	// For server requests, Host specifies the host on which the
	// URL is sought. For HTTP/1 (per RFC 7230, section 5.4), this
	// is either the value of the "Host" header or the host name
	// given in the URL itself. For HTTP/2, it is the value of the
	// ":authority" pseudo-header field.
	// It may be of the form "host:port". For international domain
	// names, Host may be in Punycode or Unicode form. Use
	// golang.org/x/net/idna to convert it to either format if
	// needed.
	// To prevent DNS rebinding attacks, server Handlers should
	// validate that the Host header has a value for which the
	// Handler considers itself authoritative. The included
	// ServeMux supports patterns registered to particular host
	// names and thus protects its registered Handlers.
	//
	// For client requests, Host optionally overrides the Host
	// header to send. If empty, the Request.Write method uses
	// the value of URL.Host. Host may contain an international
	// domain name.
	Host string

	// Form contains the parsed form data, including both the URL
	// field's query parameters and the PATCH, 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 PATCH, 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

	// Trailer specifies additional headers that are sent after the request
	// body.
	//
	// For server requests, the Trailer map initially contains only the
	// trailer keys, with nil values. (The client declares which trailers it
	// will later send.)  While the handler is reading from Body, it must
	// not reference Trailer. After reading from Body returns EOF, Trailer
	// can be read again and will contain non-nil values, if they were sent
	// by the client.
	//
	// For client requests, Trailer must be initialized to a map containing
	// the trailer keys to later send. The values may be nil or their final
	// values. The ContentLength must be 0 or -1, to send a chunked request.
	// After the HTTP request is sent the map values can be updated while
	// the request body is read. Once the body returns EOF, the caller must
	// not mutate Trailer.
	//
	// Few HTTP clients, servers, or proxies support HTTP trailers.
	Trailer Header

	// 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

	// RequestURI is the unmodified request-target of the
	// Request-Line (RFC 7230, Section 3.1.1) as sent by the client
	// to a server. Usually the URL field should be used instead.
	// It is an error to set this field in an HTTP client request.
	RequestURI string

	// TLS allows HTTP servers and other software to record
	// information about the TLS connection on which the request
	// was received. This field is not filled in by ReadRequest.
	// The HTTP server in this package sets the field for
	// TLS-enabled connections before invoking a handler;
	// otherwise it leaves the field nil.
	// This field is ignored by the HTTP client.
	TLS *tls.ConnectionState

	// Cancel is an optional channel whose closure indicates that the client
	// request should be regarded as canceled. Not all implementations of
	// RoundTripper may support Cancel.
	//
	// For server requests, this field is not applicable.
	//
	// Deprecated: Set the Request's context with NewRequestWithContext
	// instead. If a Request's Cancel field and context are both
	// set, it is undefined whether Cancel is respected.
	Cancel <-chan struct{}

	// Response is the redirect response which caused this request
	// to be created. This field is only populated during client
	// redirects.
	Response *Response

	// ctx is either the client or server context. It should only
	// be modified via copying the whole Request using WithContext.
	// It is unexported to prevent people from using Context wrong
	// and mutating the contexts held by callers of the same request.
	ctx context.Context
}

7.http.Response结构体

//简化版
type Response struct {
	Status     string // e.g. "200 OK"
	StatusCode int    // e.g. 200
	Proto      string // e.g. "HTTP/1.0"
	ProtoMajor int    // e.g. 1
	ProtoMinor int    // e.g. 0

	Header Header
	Body io.ReadCloser
	ContentLength int64
	TransferEncoding []string
	Close bool
	Uncompressed bool
	Trailer Header
	Request *Request
	TLS *tls.ConnectionState
}

//详细版
// Response represents the response from an HTTP request.
//
// The Client and Transport return Responses from servers once
// the response headers have been received. The response body
// is streamed on demand as the Body field is read.
type Response struct {
	Status     string // e.g. "200 OK"
	StatusCode int    // e.g. 200
	Proto      string // e.g. "HTTP/1.0"
	ProtoMajor int    // e.g. 1
	ProtoMinor int    // e.g. 0

	// Header maps header keys to values. If the response had multiple
	// headers with the same key, they may be concatenated, with comma
	// delimiters.  (RFC 7230, section 3.2.2 requires that multiple headers
	// be semantically equivalent to a comma-delimited sequence.) When
	// Header values are duplicated by other fields in this struct (e.g.,
	// ContentLength, TransferEncoding, Trailer), the field values are
	// authoritative.
	//
	// Keys in the map are canonicalized (see CanonicalHeaderKey).
	Header Header

	// Body represents the response body.
	//
	// The response body is streamed on demand as the Body field
	// is read. If the network connection fails or the server
	// terminates the response, Body.Read calls return an error.
	//
	// The http Client and Transport guarantee that Body is always
	// non-nil, even on responses without a body or responses with
	// a zero-length body. It is the caller's responsibility to
	// close Body. The default HTTP client's Transport may not
	// reuse HTTP/1.x "keep-alive" TCP connections if the Body is
	// not read to completion and closed.
	//
	// The Body is automatically dechunked if the server replied
	// with a "chunked" Transfer-Encoding.
	//
	// As of Go 1.12, the Body will also implement io.Writer
	// on a successful "101 Switching Protocols" response,
	// as used by WebSockets and HTTP/2's "h2c" mode.
	Body io.ReadCloser

	// ContentLength records the length of the associated content. The
	// value -1 indicates that the length is unknown. Unless Request.Method
	// is "HEAD", values >= 0 indicate that the given number of bytes may
	// be read from Body.
	ContentLength int64

	// Contains transfer encodings from outer-most to inner-most. Value is
	// nil, means that "identity" encoding is used.
	TransferEncoding []string

	// Close records whether the header directed that the connection be
	// closed after reading Body. The value is advice for clients: neither
	// ReadResponse nor Response.Write ever closes a connection.
	Close bool

	// Uncompressed reports whether the response was sent compressed but
	// was decompressed by the http package. When true, reading from
	// Body yields the uncompressed content instead of the compressed
	// content actually set from the server, ContentLength is set to -1,
	// and the "Content-Length" and "Content-Encoding" fields are deleted
	// from the responseHeader. To get the original response from
	// the server, set Transport.DisableCompression to true.
	Uncompressed bool

	// Trailer maps trailer keys to values in the same
	// format as Header.
	//
	// The Trailer initially contains only nil values, one for
	// each key specified in the server's "Trailer" header
	// value. Those values are not added to Header.
	//
	// Trailer must not be accessed concurrently with Read calls
	// on the Body.
	//
	// After Body.Read has returned io.EOF, Trailer will contain
	// any trailer values sent by the server.
	Trailer Header

	// Request is the request that was sent to obtain this Response.
	// Request's Body is nil (having already been consumed).
	// This is only populated for Client requests.
	Request *Request

	// TLS contains information about the TLS connection on which the
	// response was received. It is nil for unencrypted responses.
	// The pointer is shared between responses and should not be
	// modified.
	TLS *tls.ConnectionState
}

8.http.HandleFunc函数类型

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers. If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler that calls f.
type HandlerFunc func(ResponseWriter, *Request)