在使用go 的grpc通訊時，會有一個坑，當grpc 返回欄位為該欄位型別的預設值時，為了節省頻寬，不會傳輸該欄位，這對客戶端來說，資料結構不嚴謹，解決辦法

grpc :

import (
        pb "github.com/golang/protobuf/jsonpb"
)

func marshalJsonp(pbMsg proto.Message) (msg []byte, err error) {
	m := pb.Marshaler{EmitDefaults: true, OrigName: true}
	var data bytes.Buffer
	err = m.Marshal(&data, pbMsg)
	return data.Bytes(), err
}
 

grpc-gateway

package main

import (
  "flag"
  "net/http"

  "github.com/golang/glog"
  "golang.org/x/net/context"
  "github.com/grpc-ecosystem/grpc-gateway/runtime"
  "google.golang.org/grpc"
	
  gw "path/to/your_service_package"
)

var (
  echoEndpoint = flag.String("echo_endpoint", "localhost:9090", "endpoint of YourService")
)

func run() error {
  ctx := context.Background()
  ctx, cancel := context.WithCancel(ctx)
  defer cancel()

  mux := runtime.NewServeMux(runtime.WithMarshalerOption(runtime.MIMEWildcard, &runtime.JSONPb{OrigName: true, EmitDefaults: true})
  opts := []grpc.DialOption{grpc.WithInsecure()}
  err := gw.RegisterYourServiceHandlerFromEndpoint(ctx, mux, *echoEndpoint, opts)
  if err != nil {
    return err
  }

  return http.ListenAndServe(":8080", mux)
}

func main() {
  flag.Parse()
  defer glog.Flush()

  if err := run(); err != nil {
    glog.Fatal(err)
  }
}
 

起作用的就是下面這句配置：

 mux := runtime.NewServeMux(runtime.WithMarshalerOption(runtime.MIMEWildcard, &runtime.JSONPb{OrigName: true, EmitDefaults: true})