https://github.com/jarcoal/httpmock是一个mock http请求包，他的原理是使用MockTransport替换http包client的Transport RoundTripper，并注册请求对应的返回值。当http请求发出的时候，被mock的Transport拦截，通过路径匹配找到对应的response，实现了http请求的mock，它的使用方式如下：
代码语言：javascript复制httpmock.Activate()
defer httpmock.DeactivateAndReset()
httpmock.RegisterResponder("GET", api, httpmock.NewStringResponder(200, string(mockResponse)))然后就可以发送http请求了。下面我们分析下它的源码。
分析httpmock源码之前我们先分析下http.Client的源码。我们发起http请求的时候，调用方式如下：
代码语言：javascript复制myClient := &http.Client{}
response, err := myClient.Do(request)源码位于src/net/http/client.go
代码语言：javascript复制func (c *Client) Do(req *Request) (*Response, error) {
return c.do(req)
}func (c *Client) do(req *Request) (retres *Response, reterr error) {
if resp, didTimeout, err = c.send(req, deadline); err != nil {在发送请求前先获取RoundTripper，然后调用RoundTrip方法
代码语言：javascript复制func (c *Client) send(req *Request, deadline time.Time) (resp *Response, didTimeout func() bool, err error) {
resp, didTimeout, err = send(req, c.transport(), deadline)func send(ireq *Request, rt RoundTripper, deadline time.Time) (resp *Response, didTimeout func() bool, err error) {
resp, err = rt.RoundTrip(req)如果用户没有自己定义transport，会使用DefaultTransport
代码语言：javascript复制func (c *Client) transport() RoundTripper {
if c.Transport != nil {
return c.Transport
}
return DefaultTransport
}type Client struct {
// Transport specifies the mechanism by which individual
// HTTP requests are made.
// If nil, DefaultTransport is used.
Transport RoundTripper
}RoundTripper是client的一个属性，类型是interface，它有一个方法RoundTrip
代码语言：javascript复制type RoundTripper interface {
RoundTrip(*Request) (*Response, error)
}DefaultTransport定义在src/net/http/transport.go
代码语言：javascript复制var DefaultTransport RoundTripper = &Transport{
Proxy: ProxyFromEnvironment,
DialContext: defaultTransportDialContext(&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
}),
ForceAttemptHTTP2: true,
MaxIdleConns: 100,
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
ExpectContinueTimeout: 1 * time.Second,
}type Transport struct {
idleMu sync.Mutex
closeIdle bool // user has requested to close all idle conns
idleConn map[connectMethodKey][]*persistConn // most recently used at end
idleConnWait map[connectMethodKey]wantConnQueue // waiting getConns
idleLRU connLRU
reqMu sync.Mutex
reqCanceler map[cancelKey]func(error)
altMu sync.Mutex // guards changing altProto only
altProto atomic.Value // of nil or map[string]RoundTripper, key is URI scheme
connsPerHostMu sync.Mutex
connsPerHost map[connectMethodKey]int
connsPerHostWait map[connectMethodKey]wantConnQueue // waiting getConns
// Proxy specifies a function to return a proxy for a given
// Request. If the function returns a non-nil error, the
// request is aborted with the provided error.
//
// The proxy type is determined by the URL scheme. "http",
// "https", and "socks5" are supported. If the scheme is empty,
// "http" is assumed.
//
// If Proxy is nil or returns a nil *URL, no proxy is used.
Proxy func(*Request) (*url.URL, error)
// DialContext specifies the dial function for creating unencrypted TCP connections.
// If DialContext is nil (and the deprecated Dial below is also nil),
// then the transport dials using package net.
//
// DialContext runs concurrently with calls to RoundTrip.
// A RoundTrip call that initiates a dial may end up using
// a connection dialed previously when the earlier connection
// becomes idle before the later DialContext completes.
DialContext func(ctx context.Context, network, addr string) (net.Conn, error)
// Dial specifies the dial function for creating unencrypted TCP connections.
//
// Dial runs concurrently with calls to RoundTrip.
// A RoundTrip call that initiates a dial may end up using
// a connection dialed previously when the earlier connection
// becomes idle before the later Dial completes.
//
// Deprecated: Use DialContext instead, which allows the transport
// to cancel dials as soon as they are no longer needed.
// If both are set, DialContext takes priority.
Dial func(network, addr string) (net.Conn, error)
// DialTLSContext specifies an optional dial function for creating
// TLS connections for non-proxied HTTPS requests.
//
// If DialTLSContext is nil (and the deprecated DialTLS below is also nil),
// DialContext and TLSClientConfig are used.
//
// If DialTLSContext is set, the Dial and DialContext hooks are not used for HTTPS
// requests and the TLSClientConfig and TLSHandshakeTimeout
// are ignored. The returned net.Conn is assumed to already be
// past the TLS handshake.
DialTLSContext func(ctx context.Context, network, addr string) (net.Conn, error)
// DialTLS specifies an optional dial function for creating
// TLS connections for non-proxied HTTPS requests.
//
// Deprecated: Use DialTLSContext instead, which allows the transport
// to cancel dials as soon as they are no longer needed.
// If both are set, DialTLSContext takes priority.
DialTLS func(network, addr string) (net.Conn, error)
// TLSClientConfig specifies the TLS configuration to use with
// tls.Client.
// If nil, the default configuration is used.
// If non-nil, HTTP/2 support may not be enabled by default.
TLSClientConfig *tls.Config
// TLSHandshakeTimeout specifies the maximum amount of time waiting to
// wait for a TLS handshake. Zero means no timeout.
TLSHandshakeTimeout time.Duration
// DisableKeepAlives, if true, disables HTTP keep-alives and
// will only use the connection to the server for a single
// HTTP request.
//
// This is unrelated to the similarly named TCP keep-alives.
DisableKeepAlives bool
// DisableCompression, if true, prevents the Transport from
// requesting compression with an "Accept-Encoding: gzip"
// request header when the Request contains no existing
// Accept-Encoding value. If the Transport requests gzip on
// its own and gets a gzipped response, it's transparently
// decoded in the Response.Body. However, if the user
// explicitly requested gzip it is not automatically
// uncompressed.
DisableCompression bool
// MaxIdleConns controls the maximum number of idle (keep-alive)
// connections across all hosts. Zero means no limit.
MaxIdleConns int
// MaxIdleConnsPerHost, if non-zero, controls the maximum idle
// (keep-alive) connections to keep per-host. If zero,
// DefaultMaxIdleConnsPerHost is used.
MaxIdleConnsPerHost int
// MaxConnsPerHost optionally limits the total number of
// connections per host, including connections in the dialing,
// active, and idle states. On limit violation, dials will block.
//
// Zero means no limit.
MaxConnsPerHost int
// IdleConnTimeout is the maximum amount of time an idle
// (keep-alive) connection will remain idle before closing
// itself.
// Zero means no limit.
IdleConnTimeout time.Duration
// ResponseHeaderTimeout, if non-zero, specifies the amount of
// time to wait for a server's response headers after fully
// writing the request (including its body, if any). This
// time does not include the time to read the response body.
ResponseHeaderTimeout time.Duration
// ExpectContinueTimeout, if non-zero, specifies the amount of
// time to wait for a server's first response headers after fully
// writing the request headers if the request has an
// "Expect: 100-continue" header. Zero means no timeout and
// causes the body to be sent immediately, without
// waiting for the server to approve.
// This time does not include the time to send the request header.
ExpectContinueTimeout time.Duration
// TLSNextProto specifies how the Transport switches to an
// alternate protocol (such as HTTP/2) after a TLS ALPN
// protocol negotiation. If Transport dials an TLS connection
// with a non-empty protocol name and TLSNextProto contains a
// map entry for that key (such as "h2"), then the func is
// called with the request's authority (such as "example.com"
// or "example.com:1234") and the TLS connection. The function
// must return a RoundTripper that then handles the request.
// If TLSNextProto is not nil, HTTP/2 support is not enabled
// automatically.
TLSNextProto map[string]func(authority string, c *tls.Conn) RoundTripper
// ProxyConnectHeader optionally specifies headers to send to
// proxies during CONNECT requests.
// To set the header dynamically, see GetProxyConnectHeader.
ProxyConnectHeader Header
// GetProxyConnectHeader optionally specifies a func to return
// headers to send to proxyURL during a CONNECT request to the
// ip:port target.
// If it returns an error, the Transport's RoundTrip fails with
// that error. It can return (nil, nil) to not add headers.
// If GetProxyConnectHeader is non-nil, ProxyConnectHeader is
// ignored.
GetProxyConnectHeader func(ctx context.Context, proxyURL *url.URL, target string) (Header, error)
// MaxResponseHeaderBytes specifies a limit on how many
// response bytes are allowed in the server's response
// header.
//
// Zero means to use a default limit.
MaxResponseHeaderBytes int64
// WriteBufferSize specifies the size of the write buffer used
// when writing to the transport.
// If zero, a default (currently 4KB) is used.
WriteBufferSize int
// ReadBufferSize specifies the size of the read buffer used
// when reading from the transport.
// If zero, a default (currently 4KB) is used.
ReadBufferSize int
// nextProtoOnce guards initialization of TLSNextProto and
// h2transport (via onceSetNextProtoDefaults)
nextProtoOnce sync.Once
h2transport h2Transport // non-nil if http2 wired up
tlsNextProtoWasNil bool // whether TLSNextProto was nil when the Once fired
// ForceAttemptHTTP2 controls whether HTTP/2 is enabled when a non-zero
// Dial, DialTLS, or DialContext func or TLSClientConfig is provided.
// By default, use of any those fields conservatively disables HTTP/2.
// To use a custom dialer or TLS config and still attempt HTTP/2
// upgrades, set this to true.
ForceAttemptHTTP2 bool
}src/net/http/roundtrip.go内实现了方法：
代码语言：javascript复制 func (t *Transport) RoundTrip(req *Request) (*Response, error) {
return t.roundTrip(req)
}func (t *Transport) roundTrip(req *Request) (*Response, error) {
t.nextProtoOnce.Do(t.onceSetNextProtoDefaults)
if altRT := t.alternateRoundTripper(req); altRT != nil {
if resp, err := altRT.RoundTrip(req); err != ErrSkipAltProtocol {
if pconn.alt != nil {
// HTTP/2 path.
t.setReqCanceler(cancelKey, nil) // not cancelable with CancelRequest
resp, err = pconn.alt.RoundTrip(req)
} else {
resp, err = pconn.roundTrip(treq)
}func (t *Transport) onceSetNextProtoDefaults() {
altProto, _ := t.altProto.Load().(map[string]RoundTripper)func (t *Transport) onceSetNextProtoDefaults() {func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err error) {func (t *Transport) alternateRoundTripper(req *Request) RoundTripper {
if !t.useRegisteredProtocol(req) {
return nil
}
altProto, _ := t.altProto.Load().(map[string]RoundTripper)
return altProto[req.URL.Scheme]
}func (t *Transport) RegisterProtocol(scheme string, rt RoundTripper) {
t.altMu.Lock()
oldMap, _ := t.altProto.Load().(map[string]RoundTripper)
if _, exists := oldMap[scheme]; exists {
panic("protocol " scheme " already registered")
}
newMap := make(map[string]RoundTripper)
for k, v := range oldMap {
newMap[k] = v
}
newMap[scheme] = rt
t.altProto.Store(newMap)src/net/http/h2_bundle.go
代码语言：javascript复制func http2registerHTTPSProtocol(t *Transport, rt http2noDialH2RoundTripper) (err error) {
t.RegisterProtocol("https", rt)func http2configureTransports(t1 *Transport) (*http2Transport, error) {
if err := http2registerHTTPSProtocol(t1, http2noDialH2RoundTripper{t2}); 熟悉完http client的方法后，我们开始分析下httpmock的源码：
首先看下激活方法github.com/jarcoal/httpmock@v1.3.0/transport.go，本质上就是用mock transport替换http包的default transport，并将http.DefaultTransport保存InitialTransport便于将来恢复
代码语言：javascript复制func Activate() {
if Disabled() {
return
}
// make sure that if Activate is called multiple times it doesn't
// overwrite the InitialTransport with a mock transport.
if http.DefaultTransport != DefaultTransport {
InitialTransport = http.DefaultTransport
}
http.DefaultTransport = DefaultTransport
}可以通过环境变量禁用mock功能。
代码语言：javascript复制 var envVarName = "GONOMOCKS"// Disabled allows to test whether httpmock is enabled or not. It
// depends on GONOMOCKS environment variable.
func Disabled() bool {
return os.Getenv(envVarName) != ""
}在mock中重点依赖的几个全局变量如下
代码语言：javascript复制var DefaultTransport = NewMockTransport()
var InitialTransport = http.DefaultTransport
var oldClients = map[*http.Client]http.RoundTripper{}
var oldClientsLock sync.Mutexfunc NewMockTransport() *MockTransport {
return &MockTransport{
responders: make(map[internal.RouteKey]matchResponders),
callCountInfo: make(map[matchRouteKey]int),
}
}type MockTransport struct {
// DontCheckMethod disables standard methods check. By default, if
// a responder is registered using a lower-cased method among CONNECT,
// DELETE, GET, HEAD, OPTIONS, POST, PUT and TRACE, a panic occurs
// as it is probably a mistake.
DontCheckMethod bool
mu sync.RWMutex
responders map[internal.RouteKey]matchResponders
regexpResponders []regexpResponder
noResponder Responder
callCountInfo map[matchRouteKey]int
totalCallCount int
}mockTransport的RundTrip方法如下：
代码语言：javascript复制func (m *MockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
for fromFindIdx := 0; ; {
found, findIdx = m.findResponders(method, req.URL, fromFindIdx)
suggested = m.suggestResponder(method, req.URL)
m.callCountInfo[matchRouteKey{RouteKey: found.key, name: mr.matcher.name}]
return runCancelable(responder, internal.SetSubmatches(req, found.submatches))func (m *MockTransport) findResponders(method string, url *url.URL, fromIdx int) (
found respondersFound,
findForKeyIndex int,
) {mock结束后要还原以前的transport
代码语言：javascript复制func DeactivateAndReset() {
Deactivate()
Reset()
}func Deactivate() {
http.DefaultTransport = InitialTransport
for oldClient, oldTransport := range oldClients {
oldClient.Transport = oldTransport
delete(oldClients, oldClient)
var oldClients = map[*http.Client]http.RoundTripper{}
func Reset() {
DefaultTransport.Reset()
} func (m *MockTransport) Reset() {
m.responders = make(map[internal.RouteKey]matchResponders)下面看下注册mock返回值的方法github.com/jarcoal/httpmock@v1.3.0/response.go
代码语言：javascript复制func NewStringResponder(status int, body string) Responder {
return ResponderFromResponse(NewStringResponse(status, body))
}func ResponderFromResponse(resp *http.Response) Responder {
return func(req *http.Request) (*http.Response, error) {
res := *respfunc NewStringResponse(status int, body string) *http.Response {func RegisterResponder(method, url string, responder Responder) {
DefaultTransport.RegisterResponder(method, url, responder)
}它就是将方法，url和返回值的对应关系，提前缓存起来，方便发起请求的时候寻找：
代码语言：javascript复制func (m *MockTransport) RegisterResponder(method, url string, responder Responder) {
m.RegisterMatcherResponder(method, url, Matcher{}, responder)
}func (m *MockTransport) RegisterMatcherResponder(method, url string, matcher Matcher, responder Responder) {
mr := matchResponder{
matcher: matcher,
responder: responder,
}
if isRegexpURL(url) {
rr := regexpResponder{
origRx: url,
method: method,
rx: regexp.MustCompile(url[2:]),
responders: matchResponders{mr},
}
m.registerRegexpResponder(rr)
m.responders[key] = m.responders[key].add(mr)
m.callCountInfo[matchRouteKey{RouteKey: key, name: matcher.name}] = 0func (m *MockTransport) registerRegexpResponder(rxResp regexpResponder) {
mr := rxResp.responders[0]
for {
for i, rr := range m.regexpResponders {
if rr.method == rxResp.method && rr.origRx == rxResp.origRx {
if mr.responder == nil {
rr.responders = rr.responders.remove(mr.matcher.name)
if rr.responders == nil {
copy(m.regexpResponders[:i], m.regexpResponders[i 1:])
m.regexpResponders[len(m.regexpResponders)-1] = regexpResponder{}
m.regexpResponders = m.regexpResponders[:len(m.regexpResponders)-1]github.com/jarcoal/httpmock@v1.3.0/internal/submatches.go
代码语言：javascript复制func SetSubmatches(req *http.Request, submatches []string) *http.Request {github.com/jarcoal/httpmock@v1.3.0/match.go
代码语言：javascript复制func (mrs matchResponders) findMatchResponder(req *http.Request) *matchResponder {
for _, mr := range mrs {
copyBody.rearm()
if mr.matcher.Check(req) {
return &mrfunc (m Matcher) Check(req *http.Request) bool {
return m.fn.Check(req)
}type MatcherFunc func(req *http.Request) boolsrc/net/http/response.go
代码语言：javascript复制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
}
