在Go语言中将表单值附加到GET/POST请求中

huangapple
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英文:

Appending form value to GET/POST Requests in Go

问题

我想定义一个http.Client，它可以自动将一个表单值附加到所有的GET/POST请求中。

我尝试实现http.RoundTripper，从另一个库中复制/粘贴了这个技术来修改每个请求的头部。

  1. type Transport struct {
  2.     // Transport is the HTTP transport to use when making requests.
  3.     // It will default to http.DefaultTransport if nil.
  4.     // (It should never be an oauth.Transport.)
  5.     Transport http.RoundTripper
  6. }
  8. // Client returns an *http.Client that makes OAuth-authenticated requests.
  9. func (t *Transport) Client() *http.Client {
  10.     return &http.Client{Transport: t}
  11. }
  13. func (t *Transport) transport() http.RoundTripper {
  14.     if t.Transport != nil {
  15.         return t.Transport
  16.     }
  17.     return http.DefaultTransport
  18. }
  20. func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
  21.     // To set the Authorization header, we must make a copy of the Request
  22.     // so that we don't modify the Request we were given.
  23.     // This is required by the specification of http.RoundTripper.
  24.     req = cloneRequest(req)
  25.     req.Form.Set("foo", bar)
  27.     // Make the HTTP request.
  28.     return t.transport().RoundTrip(req)
  29. }
  31. // cloneRequest returns a clone of the provided *http.Request.
  32. // The clone is a shallow copy of the struct and its Header map.
  33. func cloneRequest(r *http.Request) *http.Request {
  34.     // shallow copy of the struct
  35.     r2 := new(http.Request)
  36.     *r2 = *r
  37.     // deep copy of the Header
  38.     r2.Header = make(http.Header)
  39.     for k, s := range r.Header {
  40.         r2.Header[k] = s
  41.     }
  42.     return r2
  43. }

然而，这并不起作用。在这个阶段，req.Form值映射似乎不存在，所以我得到了恐慌错误：
panic: runtime error: assignment to entry in nil map

我尝试在(t *Transport) RoundTrip中添加以下代码，但没有成功：

  1. err := req.ParseForm()
  2. misc.PanicIf(err)

我不知道我在做什么，有什么提示吗？

编辑：在cloneRequest方法中尝试复制req.Form值是没有意义的，因为r.Form是一个空映射。

英文:

I would like to define a http.Client that automatically appends a form value to all GET/POST requests.

I naively tried implementing http.RoundTripper as copy/pasted from another library uses this technique to modify headers for every request.

  1. type Transport struct {
  2. 	// Transport is the HTTP transport to use when making requests.
  3. 	// It will default to http.DefaultTransport if nil.
  4. 	// (It should never be an oauth.Transport.)
  5. 	Transport http.RoundTripper
  6. }
  8. // Client returns an *http.Client that makes OAuth-authenticated requests.
  9. func (t *Transport) Client() *http.Client {
  10. 	return &http.Client{Transport: t}
  11. }
  13. func (t *Transport) transport() http.RoundTripper {
  14. 	if t.Transport != nil {
  15. 		return t.Transport
  16. 	}
  17. 	return http.DefaultTransport
  18. }
  20. func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
  21. 	// To set the Authorization header, we must make a copy of the Request
  22. 	// so that we don't modify the Request we were given.
  23. 	// This is required by the specification of http.RoundTripper.
  24. 	req = cloneRequest(req)
  25.  >>	req.Form.Set("foo", bar)
  27. 	// Make the HTTP request.
  28. 	return t.transport().RoundTrip(req)
  29. }
  31. // cloneRequest returns a clone of the provided *http.Request.
  32. // The clone is a shallow copy of the struct and its Header map.
  33. func cloneRequest(r *http.Request) *http.Request {
  34. 	// shallow copy of the struct
  35. 	r2 := new(http.Request)
  36. 	*r2 = *r
  37. 	// deep copy of the Header
  38. 	r2.Header = make(http.Header)
  39. 	for k, s := range r.Header {
  40. 		r2.Header[k] = s
  41. 	}
  42. 	return r2
  43. }

This however does not work. The req.Form values map doesn't seem to exist at this stage, so I get the panic:
panic: runtime error: assignment to entry in nil map

I tried adding this to the (t *Transport) RoundTrip, but no luck:

  1. err := req.ParseForm()
  2. misc.PanicIf(err)

I've no idea what I'm doing, any tips?

EDIT: There is no point in trying to copy req.Form values in cloneRequest method, since r.Form is empty map anyway.

答案1

得分: 8

Form、PostForm和ParseForm()只在接收请求时使用。在发送请求时，传输层期望数据已经被正确编码。

你的想法是正确的，通过包装RoundTrip来实现，但你必须自己处理编码后的数据。

  1. if req.URL.RawQuery == "" {
  2.     req.URL.RawQuery = "foo=bar"
  3. } else {
  4.     req.URL.RawQuery = req.URL.RawQuery + "&" + "foo=bar"
  5. }

或者可以选择以下方式：

  1. form, _ = url.ParseQuery(req.URL.RawQuery)
  2. form.Add("boo", "far")
  3. req.URL.RawQuery = form.Encode()

如果你想避免重复的键，也可以事先检查url.Values。另外，检查Content-Type头部是否为multipart/form-data或application/x-www-form-urlencoded，以避免与其他类型的查询产生冲突，也是一个不错的主意。

英文:

Form, PostForm, and ParseForm() are only used when receiving a request. When sending a request, the Transport expects the data to be properly encoded.

You have the right idea by wrapping RoundTrip, but you have to handle the encoded data yourself.

  1. if req.URL.RawQuery == "" {
  2. 	req.URL.RawQuery = "foo=bar"
  3. } else {
  4. 	req.URL.RawQuery = req.URL.RawQuery + "&" + "foo=bar"
  5. }

or alternatively:

  1. form, _ = url.ParseQuery(req.URL.RawQuery)
  2. form.Add("boo", "far")
  3. req.URL.RawQuery = form.Encode()

You could also choose to check the url.Values beforehand, if you want to avoid duplicating keys. Checking the Content-Type header for multipart/form-data or application/x-www-form-urlencoded to avoid interaction with other types of queries may be a good idea too.

huangapple
  • 本文由 发表于 2014年12月5日 02:13:09
  • 转载请务必保留本文链接：https://go.coder-hub.com/27301051.html
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