how to handle arbitrary (json) structs

[lucas-natraj]

i haven't been able to find an example of how to support arbitrary json -> map[string]interface{}.
i've defined my message as:

message Entity {

    // The entity's key.
    string key = 1;

    // The entity's properties.
    google.protobuf.Struct data = 2;
}

as Struct seems to be the appropriate json equivalent in protobuf.

however, i am unable to invoke the corresponding REST endpoint using

{
    "key": "xyz",
    "data": {
        "name": "joe",
        "age": 28
    }
}

is there a way to support arbitrary json content and have it mapped to basically a map[string]interface{}?

not sure how I need to define my proto messages / services to support this.

[tamalsaha]

This is not a gateway question, rather what you can map into protocol buffer. The short answer is, you can't define arbitrary map[string]interface{} in protocol buffer. Please check here: https://developers.google.com/protocol-buffers/docs/proto3#oneof

To use protocol buffer, you need to know the schema of your data.

[lucas-natraj]

yeah, i understand that map[string]interface{} isn't really supported. i was just using it as an example of handling arbitrary content.

the struct message does, in fact, use oneof and I am able to receive it on the grpc service side.

however, when using the gateway, i have to send the json request body as

{
  "key": "xyz",
  "data": {
    "fields": {
      "name": {
        "stringValue": "joe"
      },
      "age": {
        "numberValue": 28
      }
    }
  }
}

which, while not ideal, does actual get parsed correctly by the gateway.
i was hoping there was a way to achieve the more natural json representation I mentioned earlier.

[tamalsaha]

I don't think you can do any better with oneof.

[tamalsaha]

As an alternative, you could use map[string]string, then deal with type conversion in your code. In that case, json form might look a bit nicer.

[lucas-natraj]

hmm.. somewhat doable, although things quickly get mucky with nested objects.

oh well.. guess i'm outta luck.

thanks for your time @tamalsaha.

[bobbytables]

I'm pretty sure this can solve this for anyone else that finds this issue: https://godoc.org/github.com/golang/protobuf/jsonpb#Unmarshal

[derekperkins]

@bobbytables Not quite sure what you mean. How does that let you map arbitrary json to a field?

[derekperkins]

This worked for us: https://developers.google.com/protocol-buffers/docs/reference/google.protobuf#struct

[vnt32]

yeah, i understand that map[string]interface{} isn't really supported. i was just using it as an example of handling arbitrary content.

the struct message does, in fact, use oneof and I am able to receive it on the grpc service side.

however, when using the gateway, i have to send the json request body as

{
  "key": "xyz",
  "data": {
    "fields": {
      "name": {
        "stringValue": "joe"
      },
      "age": {
        "numberValue": 28
      }
    }
  }
}

which, while not ideal, does actual get parsed correctly by the gateway. i was hoping there was a way to achieve the more natural json representation I mentioned earlier.

Thanks, I barely found how to use this thing, because. not in one guide google this is not written. Used shnake_case instead of camelCase based on type from proto file