Parse/Decode raw protobuf msg

[Rohan Suri]

Hello everyone,

I'm trying to find the right Java APIs to do what protoc --decode_raw and protoc --decode do.

Essentially handling two cases:

1) When I don't have the proto, and only the raw protobuf msg.

eg protoc --decode_raw < rawmsg.bin

1: "rohan"

2 {

    1: "13"

    2: "08"

    3: "94"

}

2) When I have the .proto(not the generated classes, neither the parsed .proto)

eg protoc --decode some.pkg.name.Person $proto_file_path < rawmsg.bin

name: "rohan"

dob {

     dd: "13"

     mm: "08"

     yy: "94"

}

I did dig google groups.

From those the hints I've got is

For case 1) Using CodedInputStream write my own parser? parsing bytes by making informed guesses.

https://groups.google.com/forum/#!searchin/protobuf/decode$20without$20proto|sort:relevance/protobuf/7s4YIwrQLgk/r2Yc_36OYGAJ

http://stackoverflow.com/questions/19647387/parsing-a-raw-protocol-buffer-byte-stream-in-c-sharp/19652735#19652735

http://stackoverflow.com/questions/13937882/parsing-protocol-buffers-without-knowing-the-proto

For case 2) well nothing. Everything I got assumed I have FileDescriptorProto for my .proto or instance of my message type.

Are there any add-on libraries present to handle these scenarios?

Or any logic to go about solving them?

Thanks.

[Feng Xiao]

2) requires parsing .proto files and that parser is in C++ only. 

Are there any add-on libraries present to handle these scenarios?

Or any logic to go about solving them?

Thanks.

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[Rohan Suri]

Hey Feng, thanks for your input.

Any suggestions for 1) ? Other than using CodingInputStream?

Also is it bad practise to invoke protoc compiler in a production environment?

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[Feng Xiao]

CodedInputStream is the right one to use for 1.

Invoking protoc compiler in production sounds problematic to me, though I'm not aware of any document listing it explicitly as bad practice. I would suggest avoid that and use other alternatives. For example, in Google we build a protodb which contains FileDescriptorProto of all transitively depended .proto files and use that instead of actual .proto files.

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[Rohan Suri]

You create a descriptor by using --descriptor_set_out right?

Followed by creating FileDescriptorProto by using parseFrom(FileInputStream)?

And moving forward as stated here https://groups.google.com/d/msg/protobuf/bWlJaaMmx4Q/kIYJ1-5YRb0J

[Feng Xiao]

On Wed, Apr 19, 2017 at 1:26 PM, Rohan Suri <rohan....@gmail.com> wrote:

You create a descriptor by using --descriptor_set_out right?

That's right. You can make that part of your build process and embed the generated data file into your binary however you want.

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[Rohan Suri]

Thanks a lot Feng :)