Kotlin Protobuf

Protocol Buffer generator for kotlin multiplatform or single platform.

Overview

Features

• Support data types
  • optional, repeated, map, oneof features
• Support service type (grpc)
• Support JSON format
• Export type registry
• google.api (Grpc Gateway)
• Plugin
  • kotlinx-serialization adapter (You can use protobuf serializer with ProtobufFormat)

Backlog

• Gradle Plugin
• Customize generating files for Extension (e.g. Modify field type)
• Add option infos of protobuf to generated files.
• Utilities
  • ProtobufMessage.toAny : optimize toAny usage
• Improve kotlin type mapping
  • google.protobuf.Any to kotlin.Any
  • google.protobuf.Empty to kotlin.Unit
  • some prebuilt types
  • Kotlinx serialization annotations
• Kotlin/JS
• Kotlin/Native
• Plain kotlin serializer
• Grpc Web

Note

• This will use 'package' option in proto file. (Not using java_package or other option)

Examples

• JVM Example
• Multiplatform Example

Usage

Gradle :: JVM

build.gradle.kts

plugins {
    kotlin("jvm") version "1.9.23"
    kotlin("plugin.serialization") version "1.9.23" //optional
    id("com.google.protobuf") version "0.9.4"
}

sourceSets {
    main {
        proto {
            srcDir(File(project.projectDir, "src/main/proto"))
        }
    }
}

protobuf {
    plugins {
        //If you want without kotlinx-serialization.
        //id("kotlin-protobuf-kotlin") {
        //    artifact = "kr.jadekim:kotlin-protobuf-generator:$kotlinProtobufVersion"
        //}
        id("kotlin-protobuf-kotlinx") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-kotlinx:$kotlinProtobufVersion"
        }
        id("kotlin-protobuf-converter-jvm") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-converter-jvm:$kotlinProtobufVersion"
        }
        
        id("grpc") {
            artifact = "io.grpc:protoc-gen-grpc-java:$grpcVersion"
        }
        id("kotlin-protobuf-grpc-jvm") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-grpc-jvm:$kotlinProtobufVersion"
        }
    }
    
    generateProtoTasks {
        all().forEach {
            it.plugins {
                id("kotlin-protobuf-kotlinx")
                id("kotlin-protobuf-converter-jvm")

                id("grpc")
                id("kotlin-protobuf-grpc-jvm")
            }
        }
    }
}

dependencies {
    implementation("kr.jadekim:kotlin-protobuf:$kotlinProtobufVersion")
    implementation("kr.jadekim:kotlin-protobuf-kotlinx:$kotlinProtobufVersion")
    implementation("kr.jadekim:kotlin-protobuf-grpc:$kotlinProtobufVersion")

    implementation("com.google.protobuf:protobuf-java:$protobufVersion")
    implementation("io.grpc:grpc-protobuf:$grpcVersion")
    implementation("io.grpc:grpc-stub:$grpcVersion")
    implementation("io.grpc:grpc-kotlin-stub:$grpcKotlinVersion")

    implementation("org.jetbrains.kotlinx:kotlinx-serialization-core:$kotlinxSerializationVersion")
}

Gradle :: Multiplatform

build.gradle.kts

plugins {
    kotlin("multiplatform") version "1.9.23"
    kotlin("plugin.serialization") version "1.9.23" //optional
    id("com.google.protobuf") version "0.9.4"
    `java-library`
}

sourceSets {
    main {
        proto {
            srcDir(File(project.projectDir, "src/main/proto"))
        }
    }
}

protobuf {
    plugins {
        //If you want without kotlinx-serialization.
        //id("kotlin-protobuf-kotlin") {
        //    artifact = "kr.jadekim:kotlin-protobuf-generator:$kotlinProtobufVersion"
        //}
        id("kotlin-protobuf-kotlinx") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-kotlinx:$kotlinProtobufVersion"
        }
        id("kotlin-protobuf-converter-multiplatform") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-multiplatform:$kotlinProtobufVersion"
        }
        id("kotlin-protobuf-converter-multiplatform-jvm") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-multiplatform-jvm:$kotlinProtobufVersion"
        }
        
        id("grpc") {
            artifact = "io.grpc:protoc-gen-grpc-java:$grpcVersion"
        }
        id("kotlin-protobuf-grpc-multiplatform") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-grpc-multiplatform:$kotlinProtobufVersion"
        }
        id("kotlin-protobuf-grpc-multiplatform-jvm") {
            artifact = "kr.jadekim:kotlin-protobuf-generator-grpc-multiplatform-jvm:$kotlinProtobufVersion"
        }
    }
    
    generateProtoTasks {
        all().forEach {
            it.plugins {
                id("kotlin-protobuf-kotlinx")
                id("kotlin-protobuf-converter-multiplatform")
                id("kotlin-protobuf-converter-multiplatform-jvm")

                id("grpc")
                id("kotlin-protobuf-grpc-multiplatform")
                id("kotlin-protobuf-grpc-multiplatform-jvm")
            }
        }
    }
}

kotlin {
    jvm {
        withJava()
    }
    
    sourceSets {
        val commonMain by getting {
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/kotlin-protobuf-kotlinx"))
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/kotlin-protobuf-converter-multiplatform"))
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/kotlin-protobuf-grpc-multiplatform"))

            dependencies {
                implementation("kr.jadekim:kotlin-protobuf:$kotlinProtobufVersion")
                implementation("kr.jadekim:kotlin-protobuf-kotlinx:$kotlinProtobufVersion")
                implementation("kr.jadekim:kotlin-protobuf-grpc:$kotlinProtobufVersion")
                
                implementation("org.jetbrains.kotlinx:kotlinx-serialization-core:$kotlinxSerializationVersion")
            }
        }

        val jvmMain by getting {
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/java"))
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/grpc"))
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/kotlin-protobuf-converter-multiplatform-jvm"))
            kotlin.srcDir(File(buildDir, "generated/source/proto/main/kotlin-protobuf-grpc-multiplatform-jvm"))

            dependencies {
                implementation("com.google.protobuf:protobuf-java:$protobufVersion")
                implementation("io.grpc:grpc-protobuf:$grpcVersion")
                implementation("io.grpc:grpc-stub:$grpcVersion")
                implementation("io.grpc:grpc-kotlin-stub:$grpcKotlinVersion")
            }
        }
    }
}

Options

• Set prefix to type url : kotlin-protobuf.prefix=[some_prefix]
• Generate TypeRegistry : kotlin-protobuf.type_registry=[output class]
• Generate JvmTypeRegistry : kotlin-protobuf.jvm_type_registry=[output class]
• Generate Kotlinx SerializersModules : kotlin-protobuf.serializers_modules=[output class]

Note

Option value can't have ','.

How to apply options

protobuf {
  ...
  generateProtoTasks {
    all().forEach {
      it.plugins {
        id(...) {
          option("[option string]")
        }
      }
    }
  }
}