Importing "google/protobuf/descriptor.proto" in java protocol buffers

Question

I have a .proto file definition which needs to import "google/protobuf/descriptor.proto" because I use Custom Options.

So in my .proto file I do:

import "google/protobuf/descriptor.proto";
package ...;

...

Since my file didn't compile complaining about the dependency, I got a copy of the descriptor.proto file placing it in the same directory my proto file was.

This solved the problem but I don't believe this is the correct way. Now the descriptor.proto gets compiled together with my .proto file resulting in having 2 compiled descriptor.proto at runtime:

• the one shipped with the protobuf-java-2.5.0.jar file
• the one which was compiled together with my .proto file

I think the --proto-path option should be used somehow but not entirely sure what is the correct way.

Thanks for the best practise tip here!

Answer 1

When I have used descriptor in a .proto, I have used it like

import "google/protobuf/descriptor.proto";

message AddressBook {
  required google.protobuf.FileDescriptorSet proto_files = 1;

Then to generate the java (on windows) with addressbookSD.proto in the default directory:

protoc addressbookSD.proto --java_out=./ --proto_path=./ --proto_path=<protobuf-install-directory>\src

where <protobuf-install-directory> is the protocol buffers install directory. The key point is descriptor.proto is in

<protobuf-install-directory>\src\google\protobuf

The levels in an protobuf import stament must match directories in the File system just like they would in java.

So I use <protobuf-install-directory>\src as the import directory, The directory structure must be

<protobuf-install-directory>\src
    +-- google
         +-- protobuf
             +-- descriptor.proto

Answer 2

Your protoc is not able to find the files in the default include folder for your system

https://github.com/golang/protobuf/issues/694

apt install protobuf-compiler does not put it in include folder

Use this if you are having errors like in linux machines

google/protobuf/descriptor.proto: File not found.

google/protobuf/duration.proto: File not found.

google/protobuf/timestamp.proto: File not found.

For Correct installation on linux systems

PROTOC_ZIP=protoc-3.7.1-linux-x86_64.zip
curl -OL https://github.com/protocolbuffers/protobuf/releases/download/v3.7.1/$PROTOC_ZIP
sudo unzip -o $PROTOC_ZIP -d /usr/local bin/protoc
sudo unzip -o $PROTOC_ZIP -d /usr/local 'include/*'
rm -f $PROTOC_ZIP