我一直在处理一个问题,我必须将
io.Reader
实例作为参数传递给由 api 作为端点提供的函数。我需要做的任务是将本地文件夹上传到公司的云存储。
func (s *server) uploadFileToPutIo(w http.ResponseWriter, r *http.Request) {
tokenSource := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: token})
oauthClient := oauth2.NewClient(context.TODO(), tokenSource)
client := putio.NewClient(oauthClient)
var testIO io.Reader // ?
upload, err := client.Files.Upload(context.TODO(), testIO, "test", 0)
if err != nil {
log.Fatal(err)
}
fmt.Println(upload.File)
sendResponse(w, []byte("successful"), http.StatusOK)
}
当我在 POST 方法下向此端点发出请求时
/upload
。我收到以下错误。
2021/12/01 18:28:47 http: panic serving 127.0.0.1:61057: runtime error: invalid memory address or nil pointer dereference
goroutine 8 [running]:
net/http.(*conn).serve.func1(0xc000108d20)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:1804 +0x153
panic(0x1390ae0, 0x164fdd0)
/usr/local/Cellar/go/1.16.6/libexec/src/runtime/panic.go:971 +0x499
io.copyBuffer(0x1462700, 0xc000026360, 0x0, 0x0, 0xc000170000, 0x8000, 0x8000, 0x0, 0x0, 0x13d5e01)
/usr/local/Cellar/go/1.16.6/libexec/src/io/io.go:423 +0x10b
io.Copy(...)
/usr/local/Cellar/go/1.16.6/libexec/src/io/io.go:382
github.com/putdotio/go-putio/putio.(*FilesService).Upload(0xc000010088, 0x1468390, 0xc00001c088, 0x0, 0x0, 0x13ef46f, 0x6, 0x0, 0x170d108, 0x90, ...)
/Users/barisertas/go/pkg/mod/github.com/putdotio/go-putio/[email protected]/files.go:235 +0x187
main.(*server).uploadFileToPutIo(0xc000010028, 0x1467d60, 0xc00014a2a0, 0xc000154500)
/Users/barisertas/workspace/mini-project/api/handler.go:79 +0xe5
net/http.HandlerFunc.ServeHTTP(0xc000012db0, 0x1467d60, 0xc00014a2a0, 0xc000154500)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2049 +0x44
github.com/gorilla/mux.(*Router).ServeHTTP(0xc000144000, 0x1467d60, 0xc00014a2a0, 0xc000154300)
/Users/barisertas/go/pkg/mod/github.com/gorilla/[email protected]/mux.go:210 +0xd3
net/http.serverHandler.ServeHTTP(0xc00014a000, 0x1467d60, 0xc00014a2a0, 0xc000154300)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2867 +0xa3
net/http.(*conn).serve(0xc000108d20, 0x1468400, 0xc00005e300)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:1932 +0x8cd
created by net/http.(*Server).Serve
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2993 +0x39b
2021/12/01 18:28:47 http: panic serving 127.0.0.1:61059: runtime error: invalid memory address or nil pointer dereference
goroutine 11 [running]:
net/http.(*conn).serve.func1(0xc000108dc0)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:1804 +0x153
panic(0x1390ae0, 0x164fdd0)
/usr/local/Cellar/go/1.16.6/libexec/src/runtime/panic.go:971 +0x499
io.copyBuffer(0x1462700, 0xc000026400, 0x0, 0x0, 0xc000198000, 0x8000, 0x8000, 0x0, 0x0, 0x13d5e01)
/usr/local/Cellar/go/1.16.6/libexec/src/io/io.go:423 +0x10b
io.Copy(...)
/usr/local/Cellar/go/1.16.6/libexec/src/io/io.go:382
github.com/putdotio/go-putio/putio.(*FilesService).Upload(0xc0000100c8, 0x1468390, 0xc00001c088, 0x0, 0x0, 0x13ef46f, 0x6, 0x0, 0x170d108, 0x90, ...)
/Users/barisertas/go/pkg/mod/github.com/putdotio/go-putio/[email protected]/files.go:235 +0x187
main.(*server).uploadFileToPutIo(0xc000010028, 0x1467d60, 0xc00014a380, 0xc000154800)
/Users/barisertas/workspace/mini-project/api/handler.go:79 +0xe5
net/http.HandlerFunc.ServeHTTP(0xc000012db0, 0x1467d60, 0xc00014a380, 0xc000154800)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2049 +0x44
github.com/gorilla/mux.(*Router).ServeHTTP(0xc000144000, 0x1467d60, 0xc00014a380, 0xc000154600)
/Users/barisertas/go/pkg/mod/github.com/gorilla/[email protected]/mux.go:210 +0xd3
net/http.serverHandler.ServeHTTP(0xc00014a000, 0x1467d60, 0xc00014a380, 0xc000154600)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2867 +0xa3
net/http.(*conn).serve(0xc000108dc0, 0x1468400, 0xc00005e580)
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:1932 +0x8cd
created by net/http.(*Server).Serve
/usr/local/Cellar/go/1.16.6/libexec/src/net/http/server.go:2993 +0x39b
这是我尝试使用的函数的文档:
// Upload reads from given io.Reader and uploads the file contents to Put.io
// servers under directory given by parent. If parent is negative, user's
// preferred folder is used.
//
// If the uploaded file is a torrent file, Put.io will interpret it as a
// transfer and Transfer field will be present to represent the status of the
// tranfer. Likewise, if the uploaded file is a regular file, Transfer field
// would be nil and the uploaded file will be represented by the File field.
//
// This method reads the file contents into the memory, so it should be used for
// <150MB files.
func (f *FilesService) Upload(ctx context.Context, r io.Reader, filename string, parent int64) (Upload, error) {
if filename == "" {
return Upload{}, fmt.Errorf("filename cannot be empty")
}
var buf bytes.Buffer
mw := multipart.NewWriter(&buf)
// negative parent means use user's preferred download folder.
if parent >= 0 {
err := mw.WriteField("parent_id", itoa(parent))
if err != nil {
return Upload{}, err
}
}
formfile, err := mw.CreateFormFile("file", filename)
if err != nil {
return Upload{}, err
}
_, err = io.Copy(formfile, r)
if err != nil {
return Upload{}, err
}
err = mw.Close()
if err != nil {
return Upload{}, err
}
req, err := f.client.NewRequest(ctx, "POST", "/v2/files/upload", &buf)
if err != nil {
return Upload{}, err
}
req.Header.Set("Content-Type", mw.FormDataContentType())
var response struct {
Upload
}
_, err = f.client.Do(req, &response)
if err != nil {
return Upload{}, err
}
return response.Upload, nil
}
我对将
io.Reader
实例放入函数感到困惑。在这种情况下如何正确放置 io.Reader
函数。创建后的实例如下:
var testIO io.Reader
还是我应该做一些额外的操作?
runtime error: invalid memory address or nil pointer dereference
你肯定知道,这是因为你声明了一个
io.Reader
,但没有设置它的值,所以它仍然等于接口的默认值,即nil
。
var testIO io.Reader // ?
将
io.Reader
传递给Upload
的目的是提供要上传的数据。通过传递 io.Reader
,任意数据源可以提供任意数量的字节,不受内存可用性的限制(与 []byte
不同,后者需要在上传之前将所有数据保存在内存中)。 io.Reader
通常用于为这种“流式”操作提供数据。Upload reads from given io.Reader and uploads the file contents
应该是要上传的数据来源。
io.Reader
可能是来自
os.Open()
的文件。但它可以是任何满足
io.Reader
的东西 - 例如,它也可以是
bytes.Buffer
。它甚至可能是更深奥的东西,就像针对 AWS
流行的 S3 服务进行 GetObject
API 调用的结果,它还返回满足
io.ReadCloser
的 io.Reader
。io.Reader
是 Go 接口如何允许独立库相互连接的一个很好的例子。您使用的 SDK 并不关心它传递了什么
io.Reader
;该值满足 io.Reader
就足够了,这是编译时强制执行的要求。你可以传递满足io.Reader
的任何东西,并且接口类型保证Upload()
能够正确处理它。Upload
需要
io.Reader
。如果您想传递来自 *os.File
的 os.Open
或来自 S3 GetObject 的 io.ReadCloser
之类的东西,那么这是可行的,因为 *os.File
和 io.ReadCloser
满足 io.Reader
。但由于 Upload
采用 io.Reader
,因此您可以确信它只会调用 io.Reader
中定义的函数。这意味着在调用 Upload
后,您必须自己进行任何关闭操作。确保花时间了解 io.Reader
如何使该函数的输入保持开放式,同时具体说明其期望的接口。这是 Go 中最重要的概念之一。
var testIO io.Reader
等价于:
testIO := io.Reader(nil)
所以这就是为什么你会对空指针引用感到恐慌:
2021/12/01 18:28:47 http: panic serving 127.0.0.1:61059: runtime error: invalid memory address or nil pointer dereference
goroutine 11 [running]:
是一个接口,允许人们传递通用值,只要它们实现该接口(即实现 Read
方法)。
实现了正确的 Read
方法 - 因此兼容
io.Reader
。所以尝试一下:
f, err := os.Open(uploadFilePath)
if err != nil { /* ... */ }
upload, err := client.Files.Upload(context.TODO(), f, "test", 0)
zero value
。
io.Reader
是一个接口,其零值是 nil
。因此nil pointer dereference error
。只需在将 io.Reader
传递给 Upload 之前对其进行初始化即可:file, err := os.Open("path/to/file")
// if err != nil { ... }
upload, err := client.Files.Upload(context.TODO(), file, "test", 0)
}
有人可以告诉我为什么当我尝试使用 s3 presingned url 上传数据时我的代码失败 它给出了错误签名不匹配 但是当我尝试从读取器读取完整数据到缓冲区并将其传递为字节时,NewReader 它工作正常吗?
我想将 CreateTar 函数或 io.NewSectionReader 返回的 io.Reader 传递给我的 api