Decoding a request body in Go -- Why am I getting an EOF?

Question

I'm using the Beego framework to build a web application, and I'm trying to hand it some JSON encoded data. Roughly, this is what I have:

import (
"github.com/astaxie/beego"
)

type LoginController struct {
beego.Controller
}

func (this *LoginController) Post() {
  request := this.Ctx.Request
  length := request.ContentLength
  p := make([]byte, length)
  bytesRead, err := this.Ctx.Request.Body.Read(p)
  if err == nil{
    //blah
  } else {
    //tell me the length, bytes read, and error
  }
}

Per this tutorial, the above Should Just Work (tm).

My problem is this: bytesRead, err := this.Ctx.Request.Body.Read(p) is returning 0 bytes read and the err.Error() is EOF.

The request.ContentLength, however, is a sane number of bytes (19 or more, depending on what data I type in).

I can't figure out why the request would appear to have some length, but would fail on Read. Any ideas?

It probably means some other piece of code has already read the request body. Without knowing what the rest of the program is doing, it is hard to say where exactly. — James Henstridge, Jun 09 '14 at 02:30
I'll double check with that in mind, but I'm reasonably certain that method is the only one where I'm reading a request body right now. — Chris, Jun 09 '14 at 14:15
I'm not familiar with the beego framework you're using. It might be worth checking whether it is reading the request body itself. — James Henstridge, Jun 09 '14 at 15:07

score 4 · Accepted Answer · answered Nov 29 '14 at 15:21

If you are trying to reach a JSON payload in Beego, you'll want to call

this.Ctx.Input.RequestBody

That returns a []byte array of the sent payload. You can then pass it to a function like:

var datapoint Datapoint
json.Unmarshal(this.Ctx.Input.RequestBody, &datapoint)

Where datapoint is the struct you are attempting to unmarshall your data into.

Decoding a request body in Go -- Why am I getting an EOF?

1 Answers1