英文:
how to avoid sending Content-Length header
问题
对于流式传输的HTTP端点，有没有一种方法可以不发送长度？
w.Header().Set("Content-Type", "image/jpeg")
w.Header().Set("Transfer-Encoding", "chunked")
w.Header().Del("Content-Length")
这是我得到的回复。
HTTP/1.1 200 OK
Content-Length: 0
Content-Type: image/jpeg
Date: Mon, 23 Jun 2014 10:00:59 GMT
Transfer-Encoding: chunked
Transfer-Encoding: chunked
服务器还打印了一个警告。
2014/06/23 06:04:03 http: WriteHeader调用了"chunked"的Transfer-Encoding和Content-Length为0。
英文:
For a streaming http endpoint is there a way to refrain from sending the length?
w.Header().Set("Content-Type", "image/jpeg")
w.Header().Set("Transfer-Encoding", "chunked")
w.Header().Del("Content-Length")
This is what I get back.
HTTP/1.1 200 OK
Content-Length: 0
Content-Type: image/jpeg
Date: Mon, 23 Jun 2014 10:00:59 GMT
Transfer-Encoding: chunked
Transfer-Encoding: chunked
The server prints a warning as well.
2014/06/23 06:04:03 http: WriteHeader called with both Transfer-Encoding of "chunked" and a Content-Length of 0
答案1
得分: 6
你不应该手动设置Transfer-Encoding。Go语言会为你自动设置，包括Content-Length。
curl、Go语言的http客户端或任何标准的http客户端都会自动正确读取分块或非分块的http响应。
以下是一个分块服务器的简单示例：http://play.golang.org/p/miEV7URi8P
package main
import (
"io"
"log"
"net/http"
)
// hello world, the web server
func HelloServer(w http.ResponseWriter, req *http.Request) {
w.WriteHeader(200)
for i := 0; i < 5; i++ {
io.WriteString(w, "hello, world!\n")
w.(http.Flusher).Flush()
}
}
func main() {
http.HandleFunc("/", HelloServer)
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
对于image/jpeg类型的情况，你可以将分块的决定交给Go语言处理，或者手动发送图像的N个字节，然后刷新。
英文:
You should not manually set the Transfer-Encoding. Go is going to do that for you, as well as the Content-Length.
curl, the Go http client or any standard http client will automatically read correctly chunked or non-chunked http response.
Small exmaple of chunked server: http://play.golang.org/p/miEV7URi8P
package main
import (
"io"
"log"
"net/http"
)
// hello world, the web server
func HelloServer(w http.ResponseWriter, req *http.Request) {
w.WriteHeader(200)
for i := 0; i < 5; i++ {
io.WriteString(w, "hello, world!\n")
w.(http.Flusher).Flush()
}
}
func main() {
http.HandleFunc("/", HelloServer)
err := http.ListenAndServe(":8080", nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
In a case of an image/jpeg, you can either delegate the chunked decision to Go or manually send N bytes from the image then flush.
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