func (j *JSONP) Filter(req zerver.Request, resp zerver.Response, chain zerver.FilterChain) { if req.ReqMethod() != zerver.METHOD_GET { chain(req, resp) return } callback := req.Vars().QueryVar(j.CallbackVar) if callback == "" { chain(req, resp) return } buffer := bytes.NewBuffer(make([]byte, 0, 256)) bw := wrap.BuffRespWriter{ // to avoid write header 200 first when write callback name Buffer: buffer, } resp.Wrap(func(w http.ResponseWriter, shouldClose bool) (http.ResponseWriter, bool) { bw.ResponseWriter = w bw.ShouldClose = shouldClose return &bw, shouldClose }) chain(req, resp) bw.Buffer = nil _, err := io2.WriteString(resp, callback) if err == nil { _, err = io2.WriteString(resp, "(") if err == nil { _, err = resp.Write(buffer.Bytes()) if err == nil { _, err = io2.WriteString(resp, ")") } } } if err != nil { j.log.Warn(log.M{"msg": "write jsonp response failed", "err": err.Error()}) } }