CODEWITHSUNDEEP
c++jsonserializationflatbuffers
alteredinstance
alteredinstance

Reputation: 597

Serializing a FlatBuffer object to JSON without it's schema file

I've been working with FlatBuffers as a solution for various things in my project, one of them specifically being JSON support. However, while FB natively supports JSON generation, the documentation for flatbuffers is poor, and the process is somewhat cumbersome. Right now, I am working in the Object->JSON direction. The issue I am having doesn't really arise the other way around (I think).

I currently have JSON generation working per an example I found here (line 630, JsonEnumsTest()) - by parsing a .fbs file into a flattbuffers::Parser, building and packaging my flatbuffer object, then running GenerateText() to generate a JSON string. The code I have is simpler than the example in test.cpp, and looks vaguely like this:

bool MyFBSchemaWrapper::asJson(std::string& jsonOutput)
{
    //**This is the section I don't like having to do
    std::string schemaFile;
    if (flatbuffers::LoadFile((std::string(getenv("FBS_FILE_PATH")) + "MyFBSchema.fbs").c_str(), false, &schemaFile))
    {
        flatbuffers::Parser parser;
        const char *includePaths[] = { getenv("FBS_FILE_PATH");
        parser.Parse(schemaFile.c_str(), includePaths);
    //**End bad section
        parser.opts.strict_json = true;

        flatbuffers::FlatBufferBuilder fbBuilder;
        auto testItem1 = fbBuilder.CreateString("test1");
        auto testItem2 = fbBuilder.CreateString("test2");

        MyFBSchemaBuilder myBuilder(fbBuilder);

        myBuilder.add_item1(testItem1);
        myBuilder.add_item2(testItem2);
        FinishMyFBSchemaBuffer(fbBuilder, myBuilder.finish());

        auto result = GenerateText(parser, fbBuilder.GetBufferPointer(), &jsonOutput);
        return true;
    }
    return false;
}

Here's my issue: I'd like to avoid having to include the .fbs files to set up my Parser. I don't want to clutter an already large monolithic program by adding even more random folders, directories, environment variables, etc. I'd like to be able to generate JSON from the compiled FlatBuffer schemas, and not have to search for a file to do so.

Is there a way for me to avoid having to read back in my .fbs schemas into the parser? My intuition is pointing to no, but the lack of documentation and community support on the topic of FlatBuffers & JSON is telling me there might be a way. I'm hoping that there's a way to use the already generated MyFBSchema_generated.h to create a JSON string.

Upvotes: 1

Views: 4141

Answers (1)

Aardappel
Aardappel

Reputation: 6074

Yes, see Mini Reflection in the documentation: http://google.github.io/flatbuffers/flatbuffers_guide_use_cpp.html

Upvotes: 1

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