【Request型別】

Request型別定義在request.go檔案中，用於設定一個http請求來發送給服務端。 

// 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 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 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 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. 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 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.
	//
	// 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 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, PATCH,
	// 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-URI of the
	// Request-Line (RFC 2616, Section 5.1) 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: Use the Context and WithContext methods
	// 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
}
 

常用的欄位如下

Method string  //Head,GET, POST, PUT等方法 URL *url.URL Proto      string // "HTTP/1.0" ProtoMajor int    // 1 ProtoMinor int    // 0 Header Header //頭部資訊 Body io.ReadCloser //body Host string

其中 Header Body等於Response型別中的是一致的。

【http.Get方法】

http.Get方法與http.Head方法在同一個檔案中

實現了Client型別的Get方法原始碼如下,定義在client.go中

func (c *Client) Get(url string) (resp *Response, err error) {
        req, err := NewRequest("GET", url, nil)
        if err != nil {
                return nil, err 
        }   
        return c.Do(req)
}

與http.Head 方法一樣，呼叫了NewRequest()方法，只是傳遞的引數由“HEAD” 換成了“GET”。

NewRequest()的原型如下

       func NewRequest(method, url string, body io.Reader) (*Request, error)

傳入 一個http方法（GET、HEAD、POST等）、url及body,生成一個 Request資料型別，然後通過c.Do() 傳送請求。c,Do返回Response型別資料。

【http.Get程式碼呼叫demo】

package main

import (
	"fmt"
	"net/http"
	"net/http/httputil"
	"os"
)

func main() {
	url := "http://www.baidu.com"
	response, err := http.Get(url)
	checkErr(err)

	if response.Status != "200 OK" {
		fmt.Println(response.Status)
		os.Exit(2)
	}

	b, _ := httputil.DumpResponse(response, false)
	fmt.Println("#### b ####################")
	fmt.Println(b)
	fmt.Println("##### string(b) ###################")
	fmt.Println(string(b))
	fmt.Println("########################")

	var buf [512]byte

	reader := response.Body
	for {
		n, err := reader.Read(buf[0:])
		if err != nil {
			fmt.Println("err !=nil")
			os.Exit(0)
		}
		fmt.Println("n is:", n)
		fmt.Println(string(buf[0:n]))
		os.Exit(0)
	}

}
func checkErr(err error) {
	if err != nil {
		fmt.Println("Fatal err!", err.Error())

		os.Exit(1)
	}
}