Protocol buffer3 and json

I'm using Protobuf 3.3.0, which does have a built-in JSON serializer and parser. You can use 2 functions from google/protobuf/util/json_util.h called MessageToJsonString() and JsonStringToMessage() to make your C++ generated Message objects go to and from JSON respectively.

Here's a simple test that uses them:test-protobuf.proto:

syntax = "proto3";message SearchRequest {  string query = 1;  int32 page_number = 2;  int32 result_per_page = 3;}

test-protobuf.cpp:

#include <iostream>#include <google/protobuf/util/json_util.h>#include "test-protobuf.pb.h"int main(){  std::string json_string;  SearchRequest sr, sr2;  // Populate sr.  sr.set_query(std::string("Hello!"));  sr.set_page_number(1);  sr.set_result_per_page(10);  // Create a json_string from sr.  google::protobuf::util::JsonPrintOptions options;  options.add_whitespace = true;  options.always_print_primitive_fields = true;  options.preserve_proto_field_names = true;  MessageToJsonString(sr, &json_string, options);  // Print json_string.  std::cout << json_string << std::endl;  // Parse the json_string into sr2.  google::protobuf::util::JsonParseOptions options2;  JsonStringToMessage(json_string, &sr2, options2);  // Print the values of sr2.  std::cout    << sr2.query() << ", "    << sr2.page_number() << ", "    << sr2.result_per_page() << std::endl  ;  return 0;}

You can compile these files (assuming that you have protobuf, a compiler, and CMake installed) by using the following CMakeLists.txt file (tested on Windows).

cmake_minimum_required(VERSION 3.8)project(test-protobuf)find_package(Protobuf REQUIRED)# Use static runtime for MSVCif(MSVC)  foreach(flag_var      CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE      CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)    if(${flag_var} MATCHES "/MD")      string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")    endif(${flag_var} MATCHES "/MD")  endforeach(flag_var)endif(MSVC)protobuf_generate_cpp(test-protobuf-sources test-protobuf-headers  "${CMAKE_CURRENT_LIST_DIR}/test-protobuf.proto")list(APPEND test-protobuf-sources  "${CMAKE_CURRENT_LIST_DIR}/test-protobuf.cpp")add_executable(test-protobuf ${test-protobuf-sources} ${test-protobuf-headers})target_include_directories(test-protobuf  PUBLIC    ${PROTOBUF_INCLUDE_DIRS}    ${CMAKE_CURRENT_BINARY_DIR})target_link_libraries(test-protobuf  ${PROTOBUF_LIBRARIES})

Assuming that CMakeLists.txt, test-protobuf.proto, and test-protobuf.cpp are in the same directory, here are the commands to compile and run them on Windows with Visual Studio 15 2017 and 64-bit protobuf libraries.

mkdir buildcd buildcmake -G "Visual Studio 15 2017 Win64" ..cmake --build . --config ReleaseRelease/test-protobuf

You should see the following output:

{ "query": "Hello!", "page_number": 1, "result_per_page": 10}Hello!, 1, 10

Protobuf has json api for C#. There are some json class for C# in google protobuf reference and You can find some tests in github protobuf repository for java and c++.