strict-protobuf-generator

Generate Java constructor helpers for your Protocol Buffers (proto3) messages.

This plugin enables simple, type-safe construction of Protobuf messages by generating static factory methods based on message fields.

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Features

• ✅ Constructor generation based on Protobuf message fields
• ✅ Supports proto3 optional fields (null-safe)
• ✅ Auto-generates import statements for message and enum types
• ✅ Supports nested package structures
• ✅ Easy integration with protoc via plugin

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Installation

Using Gradle (Local Development)

git clone https://github.com/protobuf-utils/strict-protobuf-generator.git
cd strict-protobuf-generator
./gradlew :protoc-plugin:installDist

This will generate the plugin binaries at

protoc-plugin/build/install/protoc-plugin

Make sure you have Java 17+ and protobuf-compiler installed in your environment.

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Example Usage

Given the following example.proto

syntax = "proto3";

package example;

option java_package = "com.example";
option java_multiple_files = true;

message User {
  string id = 1;
  optional string email = 2;
}

Run bash

protoc \
  --plugin=protoc-gen-strictproto=./scripts/protoc-gen-strictproto \
  --strictproto_out=./gen \
  --proto_path=. \
  path/to/example.proto

The generated code will look like

package com.example;

public final class UserConstructor {

    private UserConstructor() {}

    public static User from(String id, String email) {
        User.Builder builder = User.newBuilder();
        builder.setId(id);
        if (email != null) {
            builder.setEmail(email);
        }
        return builder.build();
    }
}

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Docker Support

You can use Docker to run the generator in isolation

docker compose build strictproto-dev
docker compose run --rm strictproto-dev bash scripts/generate-strictproto.sh

Make sure your .proto and scripts/ directory are available inside the container.