Myujth

I am trying to convert a protobuf object to JSON format using com.googlecode.protobuf.format.JsonFormat but the map type came out unexpected.

My message is like this

message Response 
 repeated Candidate candidates = 1;
 map<string, ErrorMessage> errors = 2;


message ErrorMessage 
 string message = 0;
 ErrorType type = 1;


enum ErrorType 
 ERROR = 0;
 WARNING = 1;

The issue is the JSON format of the Response object I created

Response response = ...
Return new ResponseEntity<>(new JsonFormat().printToString(response), HttpStatus.OK);

I expect the errors be formatted as a map keyed by the string value (of the map key)

...
"errors": 
 "someID" : 
 "message": "blah blah",
 "type": "ERROR"
 

However the actual output is (I evaluated only the new JsonFormat().printToString(response) part in intellij)

...
"errors": 
 "key": "someID",
 "value": 
 "message": "blah blah",
 "type": "ERROR"
 

I hope it's some small configuration I missed to make protobuf (or Jackson?) to be aware of the actual key value ? not using "key" and "value".

BTW, what's the point of having literal "key" and "value" field in a map type ? You can't do constituent lookup with it and you might just use a custom type/object.

This code works perfectly for me:

test.proto

syntax = "proto2";
package by.dev.madhead;
option java_outer_classname = "SO";

message Candidate 



enum ErrorType 
 ERROR = 0;
 WARNING = 1;


message ErrorMessage 
 required string message = 1;
 required ErrorType type = 2;


message Response 
 repeated Candidate candidates = 1;
 map<string, ErrorMessage> errors = 2;

App.java

public class App 
 public static void main(String args) throws InvalidProtocolBufferException 
 SO.Response response = SO.Response.newBuilder()
 .addCandidates(SO.Candidate.newBuilder().build())
 .addCandidates(SO.Candidate.newBuilder().build())
 .addCandidates(SO.Candidate.newBuilder().build())
 .putErrors("error1", SO.ErrorMessage.newBuilder().setMessage("error1").setType(SO.ErrorType.ERROR).build())
 .putErrors("error2", SO.ErrorMessage.newBuilder().setMessage("error2").setType(SO.ErrorType.WARNING).build())
 .build();

 System.out.println(JsonFormat.printer().print(response));
 

The output is:

 "candidates": [
 , 
 , 
 ],
 "errors": 
 "error1": 
 "message": "error1",
 "type": "ERROR"
 ,
 "error2": 
 "message": "error2",
 "type": "WARNING"
 
 

Which has no keys and value as you see. Make sure that you printed not the message itself, but the result of JsonFormat.printer().print(). Basically, key and values you've seen are from internal toString() implementation of Protobuf Message.

And the full class name for JsonFormat is com.google.protobuf.util.JsonFormat, not com.googlecode.protobuf.format.JsonFormat.