http - 为什么我不能将正文添加到 http 重定向？

Question

这是我尝试过的:

w.WriteHeader(301)
w.Write([]byte("Redirecting..."))
w.Header().Set("Location", "/myredirecturl")
w.Header().Set("Content-Length", contentLength) // I thought this might help

由于某些奇怪的原因，它不会添加 Location header 。
为什么golang的http包不能加body和重定向？

Answer 1

这记录在 net/http 中包裹:

type ResponseWriter

type ResponseWriter interface {
    // Header returns the header map that will be sent by WriteHeader.
    // Changing the header after a call to WriteHeader (or Write) has
    // no effect.
    Header() Header

    // Write writes the data to the connection as part of an HTTP reply.
    // If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK)
    // before writing the data.  If the Header does not contain a
    // Content-Type line, Write adds a Content-Type set to the result of passing
    // the initial 512 bytes of written data to DetectContentType.
    Write([]byte) (int, error)

    // WriteHeader sends an HTTP response header with status code.
    // If WriteHeader is not called explicitly, the first call to Write
    // will trigger an implicit WriteHeader(http.StatusOK).
    // Thus explicit calls to WriteHeader are mainly used to
    // send error codes.
    WriteHeader(int)
}

以上说明在调用 Write() 或 WriteHeader() 后不能更改 Header()。您应该将代码更改为以下内容:

w.Header().Set("Location", "/myredirecturl")
w.WriteHeader(301)
w.Write('Redirecting...')