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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// HTTP client. See RFC 2616.
//
// This is the high-level Client interface.
// The low-level implementation is in transport.go.
package http
import (
"encoding/base64"
"errors"
"fmt"
"io"
"net/url"
"strings"
)
// A Client is an HTTP client. Its zero value (DefaultClient) is a usable client
// that uses DefaultTransport.
//
// The Client's Transport typically has internal state (cached
// TCP connections), so Clients should be reused instead of created as
// needed. Clients are safe for concurrent use by multiple goroutines.
type Client struct {
// Transport specifies the mechanism by which individual
// HTTP requests are made.
// If nil, DefaultTransport is used.
Transport RoundTripper
// CheckRedirect specifies the policy for handling redirects.
// If CheckRedirect is not nil, the client calls it before
// following an HTTP redirect. The arguments req and via
// are the upcoming request and the requests made already,
// oldest first. If CheckRedirect returns an error, the client
// returns that error instead of issue the Request req.
//
// If CheckRedirect is nil, the Client uses its default policy,
// which is to stop after 10 consecutive requests.
CheckRedirect func(req *Request, via []*Request) error
// Jar specifies the cookie jar.
// If Jar is nil, cookies are not sent in requests and ignored
// in responses.
Jar CookieJar
}
// DefaultClient is the default Client and is used by Get, Head, and Post.
var DefaultClient = &Client{}
// RoundTripper is an interface representing the ability to execute a
// single HTTP transaction, obtaining the Response for a given Request.
//
// A RoundTripper must be safe for concurrent use by multiple
// goroutines.
type RoundTripper interface {
// RoundTrip executes a single HTTP transaction, returning
// the Response for the request req. RoundTrip should not
// attempt to interpret the response. In particular,
// RoundTrip must return err == nil if it obtained a response,
// regardless of the response's HTTP status code. A non-nil
// err should be reserved for failure to obtain a response.
// Similarly, RoundTrip should not attempt to handle
// higher-level protocol details such as redirects,
// authentication, or cookies.
//
// RoundTrip should not modify the request, except for
// consuming the Body. The request's URL and Header fields
// are guaranteed to be initialized.
RoundTrip(*Request) (*Response, error)
}
// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
// return true if the string includes a port.
func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
// Used in Send to implement io.ReadCloser by bundling together the
// bufio.Reader through which we read the response, and the underlying
// network connection.
type readClose struct {
io.Reader
io.Closer
}
// Do sends an HTTP request and returns an HTTP response, following
// policy (e.g. redirects, cookies, auth) as configured on the client.
//
// A non-nil response always contains a non-nil resp.Body.
//
// Callers should close resp.Body when done reading from it. If
// resp.Body is not closed, the Client's underlying RoundTripper
// (typically Transport) may not be able to re-use a persistent TCP
// connection to the server for a subsequent "keep-alive" request.
//
// Generally Get, Post, or PostForm will be used instead of Do.
func (c *Client) Do(req *Request) (resp *Response, err error) {
if req.Method == "GET" || req.Method == "HEAD" {
return c.doFollowingRedirects(req)
}
return send(req, c.Transport)
}
// send issues an HTTP request. Caller should close resp.Body when done reading from it.
func send(req *Request, t RoundTripper) (resp *Response, err error) {
if t == nil {
t = DefaultTransport
if t == nil {
err = errors.New("http: no Client.Transport or DefaultTransport")
return
}
}
if req.URL == nil {
return nil, errors.New("http: nil Request.URL")
}
if req.RequestURI != "" {
return nil, errors.New("http: Request.RequestURI can't be set in client requests.")
}
// Most the callers of send (Get, Post, et al) don't need
// Headers, leaving it uninitialized. We guarantee to the
// Transport that this has been initialized, though.
if req.Header == nil {
req.Header = make(Header)
}
if u := req.URL.User; u != nil {
req.Header.Set("Authorization", "Basic "+base64.URLEncoding.EncodeToString([]byte(u.String())))
}
return t.RoundTrip(req)
}
// True if the specified HTTP status code is one for which the Get utility should
// automatically redirect.
func shouldRedirect(statusCode int) bool {
switch statusCode {
case StatusMovedPermanently, StatusFound, StatusSeeOther, StatusTemporaryRedirect:
return true
}
return false
}
// Get issues a GET to the specified URL. If the response is one of the following
// redirect codes, Get follows the redirect, up to a maximum of 10 redirects:
//
// 301 (Moved Permanently)
// 302 (Found)
// 303 (See Other)
// 307 (Temporary Redirect)
//
// Caller should close r.Body when done reading from it.
//
// Get is a wrapper around DefaultClient.Get.
func Get(url string) (r *Response, err error) {
return DefaultClient.Get(url)
}
// Get issues a GET to the specified URL. If the response is one of the
// following redirect codes, Get follows the redirect after calling the
// Client's CheckRedirect function.
//
// 301 (Moved Permanently)
// 302 (Found)
// 303 (See Other)
// 307 (Temporary Redirect)
//
// Caller should close r.Body when done reading from it.
func (c *Client) Get(url string) (r *Response, err error) {
req, err := NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
return c.doFollowingRedirects(req)
}
func (c *Client) doFollowingRedirects(ireq *Request) (r *Response, err error) {
// TODO: if/when we add cookie support, the redirected request shouldn't
// necessarily supply the same cookies as the original.
var base *url.URL
redirectChecker := c.CheckRedirect
if redirectChecker == nil {
redirectChecker = defaultCheckRedirect
}
var via []*Request
if ireq.URL == nil {
return nil, errors.New("http: nil Request.URL")
}
jar := c.Jar
if jar == nil {
jar = blackHoleJar{}
}
req := ireq
urlStr := "" // next relative or absolute URL to fetch (after first request)
for redirect := 0; ; redirect++ {
if redirect != 0 {
req = new(Request)
req.Method = ireq.Method
req.Header = make(Header)
req.URL, err = base.Parse(urlStr)
if err != nil {
break
}
if len(via) > 0 {
// Add the Referer header.
lastReq := via[len(via)-1]
if lastReq.URL.Scheme != "https" {
req.Header.Set("Referer", lastReq.URL.String())
}
err = redirectChecker(req, via)
if err != nil {
break
}
}
}
for _, cookie := range jar.Cookies(req.URL) {
req.AddCookie(cookie)
}
urlStr = req.URL.String()
if r, err = send(req, c.Transport); err != nil {
break
}
if c := r.Cookies(); len(c) > 0 {
jar.SetCookies(req.URL, c)
}
if shouldRedirect(r.StatusCode) {
r.Body.Close()
if urlStr = r.Header.Get("Location"); urlStr == "" {
err = errors.New(fmt.Sprintf("%d response missing Location header", r.StatusCode))
break
}
base = req.URL
via = append(via, req)
continue
}
return
}
method := ireq.Method
err = &url.Error{
Op: method[0:1] + strings.ToLower(method[1:]),
URL: urlStr,
Err: err,
}
return
}
func defaultCheckRedirect(req *Request, via []*Request) error {
if len(via) >= 10 {
return errors.New("stopped after 10 redirects")
}
return nil
}
// Post issues a POST to the specified URL.
//
// Caller should close r.Body when done reading from it.
//
// Post is a wrapper around DefaultClient.Post
func Post(url string, bodyType string, body io.Reader) (r *Response, err error) {
return DefaultClient.Post(url, bodyType, body)
}
// Post issues a POST to the specified URL.
//
// Caller should close r.Body when done reading from it.
func (c *Client) Post(url string, bodyType string, body io.Reader) (r *Response, err error) {
req, err := NewRequest("POST", url, body)
if err != nil {
return nil, err
}
req.Header.Set("Content-Type", bodyType)
r, err = send(req, c.Transport)
if err == nil && c.Jar != nil {
c.Jar.SetCookies(req.URL, r.Cookies())
}
return r, err
}
// PostForm issues a POST to the specified URL,
// with data's keys and values urlencoded as the request body.
//
// Caller should close r.Body when done reading from it.
//
// PostForm is a wrapper around DefaultClient.PostForm
func PostForm(url string, data url.Values) (r *Response, err error) {
return DefaultClient.PostForm(url, data)
}
// PostForm issues a POST to the specified URL,
// with data's keys and values urlencoded as the request body.
//
// Caller should close r.Body when done reading from it.
func (c *Client) PostForm(url string, data url.Values) (r *Response, err error) {
return c.Post(url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
}
// Head issues a HEAD to the specified URL. If the response is one of the
// following redirect codes, Head follows the redirect after calling the
// Client's CheckRedirect function.
//
// 301 (Moved Permanently)
// 302 (Found)
// 303 (See Other)
// 307 (Temporary Redirect)
//
// Head is a wrapper around DefaultClient.Head
func Head(url string) (r *Response, err error) {
return DefaultClient.Head(url)
}
// Head issues a HEAD to the specified URL. If the response is one of the
// following redirect codes, Head follows the redirect after calling the
// Client's CheckRedirect function.
//
// 301 (Moved Permanently)
// 302 (Found)
// 303 (See Other)
// 307 (Temporary Redirect)
func (c *Client) Head(url string) (r *Response, err error) {
req, err := NewRequest("HEAD", url, nil)
if err != nil {
return nil, err
}
return c.doFollowingRedirects(req)
}