Kotlin DTO Generator for gRPC

The protobuf plugin generates DTO classes for the corresponding messages in your *.proto files.

The data classes in Kotlin is more convenient then the builders.

The generator makes the next steps:

1. Create a new DTO class with a simple name <message_class_name>*Dto* inside a package <java_package>*.dto*. Both suffixes for class and package are customizable.
2. Create to additional extension functions inside each file: toDto and toGrpc

The generator creates new Dto class with simple name <message_class_name>*Dto*. The prefix is customizable. The generator creates two additional extensions functions toDto and toGrpc

Some code taken from - https://github.com/grpc/grpc-kotlin. Remove as soon as possible.

Table of content

1. How to use
2. Options
3. Examples
   1. Primitives
   2. Enum
   3. One Of
   4. Optional
   5. Repeated
   6. Special scenarios

How to use

protobuf {
    protoc {
        artifact = "com.google.protobuf:protoc:${rootProject.ext["protobufVersion"]}"
    }
    plugins {
        id("grpc") {
            artifact = "io.grpc:protoc-gen-grpc-java:${rootProject.ext["grpcVersion"]}"
        }
        id("grpcdtokt") {
            artifact = "INPROGRESS"
        }
    }
    generateProtoTasks {
        all().forEach {
            if (it.name.startsWith("generateTestProto")) {
                it.dependsOn("jar")
            }

            it.plugins {
                id("grpc")
                id("grpcdtokt") {
                    option("dto_suffix=Dto")
                    option("dto_package_suffix=dto")
                }
            }
        }
    }
}

Options

Current implementation has the next options:

1. dto_suffix - DTO class suffix. Default - Dto (example: dto_suffix=DTO)
2. dto_package_suffix - DTO class package suffix. New package suffix adds to default package for proto objects. Default - dto (example: dto_package_suffix=test.example)

Examples

Primitives

All primitives has a default value.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.primitives";

package test.primitives;

message TestPrimitive {
  string stringValue = 1;
  double doubleValue = 2;
  bool booleanValue = 3;
  fixed32 fixed32Value = 4;
  fixed64 fixed64Value = 5;
  float floatValue = 6;
  int32 int32Value = 7;
  int64 int64Value = 8;
  sfixed32 sFixed32Value = 9;
  sfixed64 sFixed64Value = 10;
  sint32 sInt32Value = 11;
  sint64 sInt64Value = 12;
  uint32 uInt32Value = 13;
  uint64 uInt64Value = 14;
}

package org.avlasov.test.primitives.dto

import kotlin.Boolean
import kotlin.Double
import kotlin.Float
import kotlin.Int
import kotlin.Long
import kotlin.String
import org.avlasov.test.primitives.TestPrimitive

data class TestPrimitiveDto(
    val stringValue: String = "",
    val doubleValue: Double = 0.0,
    val booleanValue: Boolean = false,
    val fixed32Value: Int = 0,
    val fixed64Value: Long = 0,
    val floatValue: Float = 0F,
    val int32Value: Int = 0,
    val int64Value: Long = 0,
    val sFixed32Value: Int = 0,
    val sFixed64Value: Long = 0,
    val sInt32Value: Int = 0,
    val sInt64Value: Long = 0,
    val uInt32Value: Int = 0,
    val uInt64Value: Long = 0
)

fun TestPrimitive.toDto(): TestPrimitiveDto =
	TestPrimitiveDto(
		stringValue = stringValue,
		doubleValue = doubleValue,
		booleanValue = booleanValue,
		fixed32Value = fixed32Value,
		fixed64Value = fixed64Value,
		floatValue = floatValue,
		int32Value = int32Value,
		int64Value = int64Value,
		sFixed32Value = sFixed32Value,
		sFixed64Value = sFixed64Value,
		sInt32Value = sInt32Value,
		sInt64Value = sInt64Value,
		uInt32Value = uInt32Value,
		uInt64Value = uInt64Value
	)

fun TestPrimitiveDto.toGrpc(): TestPrimitive =
	TestPrimitive.newBuilder().also {
    	it.stringValue = stringValue
    	it.doubleValue = doubleValue
    	it.booleanValue = booleanValue
    	it.fixed32Value = fixed32Value
    	it.fixed64Value = fixed64Value
    	it.floatValue = floatValue
    	it.int32Value = int32Value
    	it.int64Value = int64Value
    	it.sFixed32Value = sFixed32Value
    	it.sFixed64Value = sFixed64Value
    	it.sInt32Value = sInt32Value
    	it.sInt64Value = sInt64Value
    	it.uInt32Value = uInt32Value
    	it.uInt64Value = uInt64Value
    }
    .build()

Enum

DTO enum class won’t have UNRECOGNISED value. Default value for a enum class as a field is null

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.enums";

package test.enums;

enum TestEnum {
  FIRST = 0;
  SECOND = 1;
  THIRD = 2;
}

package org.avlasov.test.enums.dto

import org.avlasov.test.enums.TestEnum

enum class TestEnumDto {
    FIRST,

    SECOND,

    THIRD
}

fun TestEnum.toDto(): TestEnumDto = TestEnumDto.valueOf(name)

fun TestEnumDto.toGrpc(): TestEnum = TestEnum.valueOf(name)

Message filed example

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.oneof";

package test.oneof;

enum OneOfEnum {
  ONE_OF_ELEMENT = 0;
}

message OneOfMessageFirst {
  OneOfEnum enumValue = 1;
}

package org.avlasov.test.oneof.dto

import org.avlasov.test.oneof.OneOfMessageFirst

data class OneOfMessageFirstDto(
    val enumValue: OneOfEnumDto? = null
)

fun OneOfMessageFirst.toDto(): OneOfMessageFirstDto =
	OneOfMessageFirstDto(
		enumValue = enumValue.toDto()
	)

fun OneOfMessageFirstDto.toGrpc(): OneOfMessageFirst =
	OneOfMessageFirst.newBuilder().also {
        if (enumValue != null) {
            it.enumValue = enumValue.toGrpc()
        }
    }
    .build()

One Of

By default all objects under oneOf tag is nullable types. You can set only one object. The generator set value if and only if Protobuf message has the value and if DTO value is not null.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.oneof";

package test.oneof;

enum OneOfEnum {
  ONE_OF_ELEMENT = 0;
}

message OneOfMessageFirst {
  OneOfEnum enumValue = 1;
}

message OneOfMessageSecond {
  double doubleValue = 1;
}

message TestOneOf {
  oneof simple_oneOf {
      string stringOneOf = 1;
      OneOfMessageFirst firstMessage = 2;
      OneOfMessageSecond secondMessage = 3;
  }
}

package org.avlasov.test.oneof.dto

import org.avlasov.test.oneof.OneOfEnum

enum class OneOfEnumDto {
    ONE_OF_ELEMENT
}

fun OneOfEnum.toDto(): OneOfEnumDto = OneOfEnumDto.valueOf(name)

fun OneOfEnumDto.toGrpc(): OneOfEnum = OneOfEnum.valueOf(name)

package org.avlasov.test.oneof.dto

import org.avlasov.test.oneof.OneOfMessageFirst

data class OneOfMessageFirstDto(
    val enumValue: OneOfEnumDto? = null
)

fun OneOfMessageFirst.toDto(): OneOfMessageFirstDto =
	OneOfMessageFirstDto(
		enumValue = enumValue.toDto()
	)

fun OneOfMessageFirstDto.toGrpc(): OneOfMessageFirst =
	OneOfMessageFirst.newBuilder().also {
        if (enumValue != null) {
            it.enumValue = enumValue.toGrpc()
        }
    }
    .build()

package org.avlasov.test.oneof.dto

import kotlin.Double
import org.avlasov.test.oneof.OneOfMessageSecond

data class OneOfMessageSecondDto(
    val doubleValue: Double = 0.0
)

fun OneOfMessageSecond.toDto(): OneOfMessageSecondDto =
	OneOfMessageSecondDto(
		doubleValue = doubleValue
	)

fun OneOfMessageSecondDto.toGrpc(): OneOfMessageSecond =
	OneOfMessageSecond.newBuilder().also {
    	it.doubleValue = doubleValue
    }
    .build()

package org.avlasov.test.oneof.dto

import kotlin.String
import org.avlasov.test.oneof.TestOneOf

data class TestOneOfDto(
    val stringOneOf: String? = null,
    val firstMessage: OneOfMessageFirstDto? = null,
    val secondMessage: OneOfMessageSecondDto? = null
)

fun TestOneOf.toDto(): TestOneOfDto =
	TestOneOfDto(
		stringOneOf = if (hasStringOneOf()) stringOneOf else null,
		firstMessage = if (hasFirstMessage()) firstMessage.toDto() else null,
		secondMessage = if (hasSecondMessage()) secondMessage.toDto() else null
	)

fun TestOneOfDto.toGrpc(): TestOneOf =
	TestOneOf.newBuilder().also {
        if (stringOneOf != null) {
            it.stringOneOf = stringOneOf
        }
        if (firstMessage != null) {
            it.firstMessage = firstMessage.toGrpc()
        }
        if (secondMessage != null) {
            it.secondMessage = secondMessage.toGrpc()
        }
    }
    .build()

Optional

Any field marked as optional is nullable by default.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.optional";

package test.optional;

message OptionalObject {
  bool test = 1;
}

message TestOptional {
  optional OptionalObject optionalObject = 1;
  optional string str = 2;
}

package org.avlasov.test.optional.dto

import kotlin.Boolean
import org.avlasov.test.optional.OptionalObject

data class OptionalObjectDto(
    val test: Boolean = false
)

fun OptionalObject.toDto(): OptionalObjectDto =
	OptionalObjectDto(
		test = test
	)

fun OptionalObjectDto.toGrpc(): OptionalObject =
	OptionalObject.newBuilder().also {
    	it.test = test
    }
    .build()

package org.avlasov.test.optional.dto

import kotlin.String
import org.avlasov.test.optional.TestOptional

data class TestOptionalDto(
    val optionalObject: OptionalObjectDto? = null,
    val str: String? = null
)

fun TestOptional.toDto(): TestOptionalDto =
	TestOptionalDto(
		optionalObject = if (hasOptionalObject()) optionalObject.toDto() else null,
		str = if (hasStr()) str else null
	)

fun TestOptionalDto.toGrpc(): TestOptional =
	TestOptional.newBuilder().also {
        if (optionalObject != null) {
            it.optionalObject = optionalObject.toGrpc()
        }
        if (str != null) {
            it.str = str
        }
    }
    .build()

Repeated

By default all fields marked as repeated has default value listOf(). The content of the repeated list converts from gRPC -> DTO and vice versa.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.oneof";

package test.oneof;

enum OneOfEnum {
  ONE_OF_ELEMENT = 0;
}

message OneOfMessageFirst {
  OneOfEnum enumValue = 1;
}

message OneOfMessageSecond {
  double doubleValue = 1;
}

message TestOneOf {
  oneof simple_oneOf {
      string stringOneOf = 1;
      OneOfMessageFirst firstMessage = 2;
      OneOfMessageSecond secondMessage = 3;
  }
}

package org.avlasov.test.repeated.dto

import kotlin.Boolean
import org.avlasov.test.repeated.RepeatedObject

data class RepeatedObjectDto(
    val test: Boolean = false
)

fun RepeatedObject.toDto(): RepeatedObjectDto =
	RepeatedObjectDto(
		test = test
	)

fun RepeatedObjectDto.toGrpc(): RepeatedObject =
	RepeatedObject.newBuilder().also {
    	it.test = test
    }
    .build()

package org.avlasov.test.repeated.dto

import kotlin.Int
import kotlin.String
import kotlin.collections.List
import org.avlasov.test.repeated.TestRepeated

data class TestRepeatedDto(
    val objects: List<RepeatedObjectDto> = listOf(),
    val strings: List<String> = listOf(),
    val ints: List<Int> = listOf()
)

fun TestRepeated.toDto(): TestRepeatedDto =
	TestRepeatedDto(
		objects = objectsList.map { it.toDto() },
		strings = stringsList,
		ints = intsList
	)

fun TestRepeatedDto.toGrpc(): TestRepeated =
	TestRepeated.newBuilder().also {
    	it.addAllObjects(objects.map { o -> o.toGrpc() })
    	it.addAllStrings(strings)
    	it.addAllInts(ints)
    }
    .build()

Special scenarios

One of the special scenarios is the message that not generates as DTO. For example: type - google.protobuf.Any

NOTE At this moment the feature is not fully covered. Please, fill free to contribute or create an issue.

syntax = "proto3";

option java_multiple_files = true;
option java_package = "org.avlasov.test.special";

import "google/protobuf/any.proto";

package test.special;

message TestSpecial {
  string message = 1;
  repeated google.protobuf.Any details = 2;
}

package org.avlasov.test.special.dto

import com.google.protobuf.Any
import kotlin.String
import kotlin.collections.List
import org.avlasov.test.special.TestSpecial

data class TestSpecialDto(
    val message: String = "",
    val details: List<Any> = listOf()
)

fun TestSpecial.toDto(): TestSpecialDto =
	TestSpecialDto(
		message = message,
		details = detailsList
	)

fun TestSpecialDto.toGrpc(): TestSpecial =
	TestSpecial.newBuilder().also {
    	it.message = message
    	it.addAllDetails(details)
    }
    .build()