# Simple Service using gRPC & Spring Boot

Paul Tomoiu

●

Examples,

Spring,

Spring Boot,

gRPC

●

Published 2022-12-03

This tutorial explains how to create a server using gRPC and Spring Boot. You will have an example as well.

The first step is to create a simple web Spring Boot application. I did it using Spring Initializr.

Here are the steps for creating a

Step #1 - add the following properties in the pox.xml

<properties>
   <grpc.version>1.42.1</grpc.version>
   <protobuf-maven-plugin.version>0.6.1</protobuf-maven-plugin.version>
</properties>

Step #2 - add the following dependencies in the pox.xml

<dependency>
        <groupId>net.devh</groupId>
        <artifactId>grpc-spring-boot-starter</artifactId>
        <version>2.14.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-stub</artifactId>
        <version>${grpc.version}</version>
    </dependency>
    <dependency>
        <groupId>io.grpc</groupId>
        <artifactId>grpc-protobuf</artifactId>
        <version>${grpc.version}</version>
    </dependency>
    <dependency>
        <!-- Java 9+ compatibility -->
        <groupId>jakarta.annotation</groupId>
        <artifactId>jakarta.annotation-api</artifactId>
        <version>1.3.5</version>
        <optional>true</optional>
</dependency>

Step #3 - add the following extension in the pox.xml

<extension>
    <groupId>kr.motd.maven</groupId>
    <artifactId>os-maven-plugin</artifactId>
    <version>1.6.1</version>
</extension>

Step #4 - add the following plugin in the pox.xml

<plugin>
    <groupId>org.xolstice.maven.plugins</groupId>
    <artifactId>protobuf-maven-plugin</artifactId>
    <version>${protobuf-maven-plugin.version}</version>
    <configuration>
        <protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.16.1:exe:${os.detected.classifier}</pluginArtifact>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
                <goal>compile-custom</goal>
            </goals>
        </execution>
    </executions>
</plugin>

Here is the full pom.xml file I have used for my example:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.10</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>grpc-service</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>grpc-service</name>
	<description>Demo project for Spring Boot and gRPC Service</description>
	<properties>
		<java.version>17</java.version>

		<grpc.version>1.42.1</grpc.version>
		<protobuf-maven-plugin.version>0.6.1</protobuf-maven-plugin.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>net.devh</groupId>
			<artifactId>grpc-spring-boot-starter</artifactId>
			<version>2.14.0.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>io.grpc</groupId>
			<artifactId>grpc-stub</artifactId>
			<version>${grpc.version}</version>
		</dependency>
		<dependency>
			<groupId>io.grpc</groupId>
			<artifactId>grpc-protobuf</artifactId>
			<version>${grpc.version}</version>
		</dependency>
		<dependency>
			<!-- Java 9+ compatibility -->
			<groupId>jakarta.annotation</groupId>
			<artifactId>jakarta.annotation-api</artifactId>
			<version>1.3.5</version>
			<optional>true</optional>
		</dependency>

	</dependencies>

	<build>
		<extensions>
			<extension>
				<groupId>kr.motd.maven</groupId>
				<artifactId>os-maven-plugin</artifactId>
				<version>1.6.1</version>
			</extension>
		</extensions>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<configuration>
					<excludes>
						<exclude>
							<groupId>org.projectlombok</groupId>
							<artifactId>lombok</artifactId>
						</exclude>
					</excludes>
				</configuration>
			</plugin>

			<plugin>
				<groupId>org.xolstice.maven.plugins</groupId>
				<artifactId>protobuf-maven-plugin</artifactId>
				<version>${protobuf-maven-plugin.version}</version>
				<configuration>
					<protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
					<pluginId>grpc-java</pluginId>
					<pluginArtifact>io.grpc:protoc-gen-grpc-java:1.16.1:exe:${os.detected.classifier}</pluginArtifact>
				</configuration>
				<executions>
					<execution>
						<goals>
							<goal>compile</goal>
							<goal>compile-custom</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>

</project>

Step #5 - create the proto & services directory as in the following picture:

Step #6 - define the service(s) and data structures (messages) in the proto file

prototext
syntax = "proto3";

package proto;

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

service MyService {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {
  }
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
  string message_code = 2;
}

Step #6 - implement the service

package com.example.grpc.services;

import com.example.from.proto.HelloReply;
import com.example.from.proto.HelloRequest;
import com.example.from.proto.MyServiceGrpc;

import io.grpc.stub.StreamObserver;

import net.devh.boot.grpc.server.service.GrpcService;

@GrpcService
public class MyServiceImpl extends MyServiceGrpc.MyServiceImplBase {

    @Override
    public void sayHello(HelloRequest request, StreamObserver<HelloReply> responseObserver) {
        HelloReply reply = HelloReply.newBuilder()
                .setMessage("Hello " + request.getName() + " !")
                .setMessageCode("2020")
                .build();
        responseObserver.onNext(reply);
        responseObserver.onCompleted();
    }

}

Info

At this point the following imports will not work.

import com.example.from.proto.HelloReply;
import com.example.from.proto.HelloRequest;
import com.example.from.proto.MyServiceGrpc;

We need to run mvn clean install in order to generate these classes.

Please take a look at target directory to see all generated files:

The main Java class has nothing special:

package com.example.grpc;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class GrpcServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(GrpcServiceApplication.class, args);
	}
}

After mvn clean install we can start the application and test it using BloomRPC or other gRPC clients.

The port could be changed in application.properties using grpc.server.port=9091.