问题
I have a written a simple GRPC server and a client to call the server (both in Go). Please tell me if using golang/protobuf/struct is the best way to send a dynamic JSON with GRPC.
In the example below, earlier I was creating Details as a map[string]interface{} and serializing it. Then I was sending it in protoMessage as bytes and was de-serializing the message on the server side.
Is it the best/efficient way to do it or should I define Details as a struct in my proto file?
Below is User.proto file
syntax = "proto3";
package messages;
import "google/protobuf/struct.proto";
service UserService {
rpc SendJson (SendJsonRequest) returns (SendJsonResponse) {}
}
message SendJsonRequest {
string UserID = 1;
google.protobuf.Struct Details = 2;
}
message SendJsonResponse {
string Response = 1;
}
Below is client.go file
package main
import (
"context"
"flag"
pb "grpc-test/messages/pb"
"log"
"google.golang.org/grpc"
)
func main() {
var serverAddr = flag.String("server_addr", "localhost:5001", "The server address in the format of host:port")
opts := []grpc.DialOption{grpc.WithInsecure()}
conn, err := grpc.Dial(*serverAddr, opts...)
if err != nil {
log.Fatalf("did not connect: %s", err)
}
defer conn.Close()
userClient := pb.NewUserServiceClient(conn)
ctx := context.Background()
sendJson(userClient, ctx)
}
func sendJson(userClient pb.UserServiceClient, ctx context.Context) {
var item = &structpb.Struct{
Fields: map[string]*structpb.Value{
"name": &structpb.Value{
Kind: &structpb.Value_StringValue{
StringValue: "Anuj",
},
},
"age": &structpb.Value{
Kind: &structpb.Value_StringValue{
StringValue: "Anuj",
},
},
},
}
userGetRequest := &pb.SendJsonRequest{
UserID: "A123",
Details: item,
}
res, err := userClient.SendJson(ctx, userGetRequest)
}
回答1:
I ended up using a two-step conversion with protojson, from map to json to struct:
m := map[string]interface{}{
"foo":"bar",
"baz":123,
}
b, err := json.Marshal(m)
s := &structpb.Struct{}
err = protojson.Unmarshal(b, s)
I don't find it elegant but could not really find any official documentation of how to do this differently. I also prefer to produce structures using "official" functions rather than trying to build a structure myself.
回答2:
If you have JSON data already, you could also choose to encode it as a string field. Otherwise, using a google.protobuf.Struct seems pretty reasonable, and you should be able to use jsonpb to convert between the Struct and JSON easily on the client and server.
回答3:
Based on this proto file.
syntax = "proto3";
package messages;
import "google/protobuf/struct.proto";
service UserService {
rpc SendJson (SendJsonRequest) returns (SendJsonResponse) {}
}
message SendJsonRequest {
string UserID = 1;
google.protobuf.Struct Details = 2;
}
message SendJsonResponse {
string Response = 1;
}
I think it is a good solution to use the google.protobuf.Struct type.
The folks with their answers, helped me a lot at the beginning, so I would like to say thanks for your work! :) I really appreciate both solutions! :)
On the other hand, I think I found a better one to produce these kinds of Structs.
Anuj's Solution
This is a little bit overcomplicated but it can work.
var item = &structpb.Struct{
Fields: map[string]*structpb.Value{
"name": &structpb.Value{
Kind: &structpb.Value_StringValue{
StringValue: "Anuj",
},
},
"age": &structpb.Value{
Kind: &structpb.Value_StringValue{
StringValue: "Anuj",
},
},
},
}
Luke's Solution
This is a shorter one but still require more conversion than necessary. map[string]interface{} -> bytes -> Struct
m := map[string]interface{}{
"foo":"bar",
"baz":123,
}
b, err := json.Marshal(m)
s := &structpb.Struct{}
err = protojson.Unmarshal(b, s)
The solution from my perspective
My solution will use the official functions from the structpb package which is pretty well documented and user friendly.
Documentation: https://pkg.go.dev/google.golang.org/protobuf/types/known/structpb
For example, this code creates a *structpb.Struct via the function that was designed to do this.
m := map[string]interface{}{
"name": "Anuj",
"age": 23,
}
details, err := structpb.NewStruct(m) // Check to rules below to avoid errors
if err != nil {
panic(err)
}
userGetRequest := &pb.SendJsonRequest{
UserID: "A123",
Details: details,
}
One of the most important thing, that we should keep in mind when we are building Struct from a map[string]interface{} is this:
https://pkg.go.dev/google.golang.org/protobuf/types/known/structpb#NewValue
// NewValue constructs a Value from a general-purpose Go interface.
//
// ╔════════════════════════╤════════════════════════════════════════════╗
// ║ Go type │ Conversion ║
// ╠════════════════════════╪════════════════════════════════════════════╣
// ║ nil │ stored as NullValue ║
// ║ bool │ stored as BoolValue ║
// ║ int, int32, int64 │ stored as NumberValue ║
// ║ uint, uint32, uint64 │ stored as NumberValue ║
// ║ float32, float64 │ stored as NumberValue ║
// ║ string │ stored as StringValue; must be valid UTF-8 ║
// ║ []byte │ stored as StringValue; base64-encoded ║
// ║ map[string]interface{} │ stored as StructValue ║
// ║ []interface{} │ stored as ListValue ║
// ╚════════════════════════╧════════════════════════════════════════════╝
//
// When converting an int64 or uint64 to a NumberValue, numeric precision loss
// is possible since they are stored as a float64.
For example, if you would like to produce a Struct that has a string list in its JSON form, you should create the following map[string]interface{}
m := map[string]interface{}{
"name": "Anuj",
"age": 23,
"cars": []interface{}{
"Toyota",
"Honda",
"Dodge",
}
}
Sorry for the long post, I hope it makes your work easier with proto3 and Go! :)
来源：https://stackoverflow.com/questions/52966444/is-google-protobuf-struct-proto-the-best-way-to-send-dynamic-json-over-grpc