gRPC is a powerful framework for communication between backend services. Combined with Java and Micronaut, it provides a practical foundation for building lightweight, strongly typed microservices.
In this tutorial, you'll learn how to get started with a Java gRPC service, build the project with Maven, and run a sample client-server interaction.
You can follow along using GRPCMicroService v1, the free starter project, available on GitHub under the MIT License. If you're looking for a more complete solution with additional features, GRPCMicroService v2 is available as a paid starter kit.
- Free v1: Browse the GitHub repository
- Paid v2: Discover the Complete Starter Kit
Why Use gRPC with Micronaut?
gRPC uses Protocol Buffers to define service contracts and exchange structured messages between clients and servers.
Some of its key benefits include:
-
Strongly typed contracts: Define service methods and message structures using
.protofiles. - Efficient communication: Use HTTP/2 and Protocol Buffers for remote procedure calls.
- Code generation: Generate client and server classes from service definitions.
- Microservice architecture: Build services with clearly defined interfaces.
- Java ecosystem: Use familiar tools such as Maven and your preferred Java IDE.
Micronaut provides the framework for building JVM applications, while gRPC handles service-to-service communication.
Together, they offer a practical foundation for developing Java microservices.
Prerequisites
Before getting started, make sure you have:
- JDK 21
- Apache Maven
- Eclipse IDE or another Java IDE (optional)
- Basic knowledge of Java and Maven
Verify your environment by running:
java -version
mvn -version
Make sure your terminal and IDE are configured to use a compatible JDK.
Step 1: Get the Free Starter Project
For this tutorial, we'll use GRPCMicroService v1, a free starter project that demonstrates the essential components of a Java gRPC microservice.
Clone the repository:
git clone https://github.com/frekost/grpc-micronaut-starter-kit.git
cd grpc-micronaut-starter-kit
You can also download the source code directly from the GitHub repository.
Import the Project into Eclipse
If you're using Eclipse, follow these steps:
- Open Eclipse.
- Select File → Import.
- Choose Maven → Existing Maven Projects.
- Select the project directory containing
pom.xml. - Finish the import and wait for Maven dependencies to resolve.
You can also open the project in your preferred Java IDE.
Step 2: Build and Test the Application
Open a terminal in the project directory and run:
mvn clean compile test
This command cleans the previous build output, compiles the project, and executes the configured tests.
If everything is configured correctly, Maven should finish with:
BUILD SUCCESS
This confirms that the build and configured tests completed successfully.
Step 3: Run the Application
In Eclipse, locate the application's main class, Application.java, and select:
Run As → Java Application
The sample project uses gRPC port 50052.
Once the server is running, the included client runner can send a request to the Greeter service.
The expected output is similar to:
Processing request with name: "Micronaut"
Response from gRPC server: Hello, Micronaut!
The exact output depends on the implementation and application configuration.
For a more detailed walkthrough, follow the Free v1 Quick Start Guide.
Step 4: Understand the Project Structure
A typical Java gRPC microservice contains several important components.
Protocol Buffers
The .proto file defines the service contract, request messages, and response messages.
These definitions provide a structured interface between the client and the server.
Service Implementation
The server-side implementation contains the business logic executed when a client calls an RPC method.
This is where you can start adapting the example to your own requirements.
gRPC Client
The client connects to the server and invokes methods defined in the service contract.
In the sample project, the client demonstrates how to send a request to the Greeter service and receive a response.
Maven Configuration
The pom.xml file manages dependencies, build plugins, and Protocol Buffers code generation.
Maven helps keep the project build reproducible and makes it easier to manage dependencies as the application evolves.
Tests
Automated tests help verify application behavior and catch regressions as the project changes.
Together, these components provide a practical starting point for developing and extending a gRPC-based microservice.
What's Next?
Once your service is running, you can explore more advanced topics:
- Adding new RPC methods
- Defining additional Protocol Buffers messages
- Implementing error handling and validation
- Configuring deadlines and timeouts
- Adding authentication and authorization
- Integrating logging and observability
- Introducing asynchronous event processing
- Exploring messaging systems such as Apache Kafka
- Containerizing and deploying your service
These are useful next steps when moving from a local example to a more complete microservice architecture.
You can implement these capabilities yourself, or start from a project that already includes some of the additional building blocks.
Free v1 vs. Paid v2
GRPCMicroService is available in two versions, designed for different needs.
GRPCMicroService v1 — Free
The free v1 project is designed for developers who want to learn how Java, Micronaut, gRPC, and Protocol Buffers work together.
It includes:
- A working gRPC Greeter service and client
- Protocol Buffers definitions
- Maven build configuration and code generation
- Micronaut application configuration
- Error-handling components
- Automated tests and technical documentation
The source code is available on GitHub under the MIT License, allowing you to use, modify, and redistribute it under the terms of that license.
Get started for free:
GRPCMicroService v2 — Complete Starter Kit
If you need more than the basic example, GRPCMicroService v2 extends the starter-kit concept with additional features for building Java microservices.
Depending on your requirements, these capabilities can help you explore more advanced application patterns without assembling every component from scratch.
The v2 starter kit includes additional capabilities such as:
- Event handling — Building blocks for event-driven workflows.
- Apache Kafka integration — Exploring messaging and asynchronous communication between services.
- Logging — Additional support for application diagnostics.
- Error handling — Components for managing errors across the application.
- Source code and automated tests — A more complete project to study, test, and adapt.
The paid v2 package is intended for developers who want a more complete starting point and prefer to spend less time assembling the initial project structure and supporting components.
Looking for the complete starter kit?
Discover GRPCMicroService v2 on Gumroad →
Review the product page for the package details and the applicable license terms.
Final Thoughts
Java, Micronaut, and gRPC are a useful combination for building services with clearly defined APIs and strongly typed communication.
Starting with a working example can help you understand the essential components before extending the service to meet your own requirements.
If you're learning gRPC or want a free foundation for your experiments, GRPCMicroService v1 is a good place to start.
If you're looking for additional capabilities, including event handling and Apache Kafka integration, GRPCMicroService v2 offers a more complete, paid starter kit.
Choose the version that fits your needs, explore the code, and start building your own Java gRPC microservices.
Have you used gRPC with Java or Micronaut? Share your experience and lessons learned in the comments!
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