Golang将文件从URL保存到AppEngine中的GCS存储桶

Question

I'm trying to get a image file from URL and save it to GCS storage using the documentation here.

I can't figure out how to create the file from response.Body to GSC given my AppEngine environment... I can't create using os.Create and reference a file path in this environment, right?

• Looking for tips on passing the response.Body to the wc.Write() method while deployed in AppEngine.

Code to get file:

func main() {
    url := "http://i.imgur.com/m1UIjW1.jpg"
    // don't worry about errors
    response, e := http.Get(url)
    if e != nil {
        log.Fatal(e)
    }

    defer response.Body.Close()

    //open a file for writing
    file, err := os.Create("/tmp/asdf.jpg")
    if err != nil {
        log.Fatal(err)
    }
    // Use io.Copy to just dump the response body to the file. This supports huge files
    _, err = io.Copy(file, response.Body)
    if err != nil {
        log.Fatal(err)
    }
    file.Close()
    fmt.Println("Success!")
} 

Save a local file to GCS

func (d *demo) createFile(fileName string) {
        fmt.Fprintf(d.w, "Creating file /%v/%v
", d.bucketName, fileName)

        wc := d.bucket.Object(fileName).NewWriter(d.ctx)
        wc.ContentType = "text/plain"
        wc.Metadata = map[string]string{
                "x-goog-meta-foo": "foo",
                "x-goog-meta-bar": "bar",
        }
        d.cleanUp = append(d.cleanUp, fileName)

        if _, err := wc.Write([]byte("abcde
")); err != nil {
                d.errorf("createFile: unable to write data to bucket %q, file %q: %v", d.bucketName, fileName, err)
                return
        }
        if _, err := wc.Write([]byte(strings.Repeat("f", 1024*4) + "
")); err != nil {
                d.errorf("createFile: unable to write data to bucket %q, file %q: %v", d.bucketName, fileName, err)
                return
        }
        if err := wc.Close(); err != nil {
                d.errorf("createFile: unable to close bucket %q, file %q: %v", d.bucketName, fileName, err)
                return
        }
}

Answer 1

It seems like you are looking for a Writer and a bytes.Buffer:

var buff bytes.Buffer
writer := NewWriter(buff)
n, err := io.Copy(writer, response.Body)