DEV Community: frekost

gRPC vs REST in Java: 7 Things Every Microservices Developer Should Know

frekost — Sat, 31 Oct 2026 16:33:44 +0000

gRPC vs REST in Java: 7 Things Every Microservices Developer Should Know

When building microservices in Java, one important architectural decision is choosing how services communicate.

For years, REST has been the default choice. But gRPC is becoming an increasingly interesting alternative, especially when performance, strongly typed contracts, and efficient service-to-service communication matter.

So, what's the difference? And when should you choose one over the other?

Let's explore seven things every Java microservices developer should know.

REST uses JSON, while gRPC uses Protocol Buffers

REST APIs commonly exchange data using JSON.

JSON is human-readable, easy to debug, and supported by almost every programming language.

gRPC uses Protocol Buffers (Protobuf), a compact binary serialization format.

Instead of defining your API through JSON examples or separate documentation, you describe your service in a ".proto" file.

For example:

syntax = "proto3";

service Greeter {
rpc SayHello (HelloRequest) returns (HelloReply);
}

message HelloRequest {
string name = 1;
}

message HelloReply {
string message = 1;
}

From this definition, gRPC can generate client and server code.

Why does this matter?

Strongly typed service contracts.
Less repetitive boilerplate.
Compact message serialization.
Code generation for multiple programming languages.

gRPC is built around HTTP/2

REST commonly uses HTTP/1.1, although it can also run over HTTP/2.

gRPC is designed around HTTP/2 and takes advantage of several of its capabilities:

Multiplexing: multiple requests can share a single connection.
Header compression: reduces repeated header overhead.
Binary framing: provides an efficient transport format.
Streaming: supports continuous data exchange.

These features make gRPC particularly interesting for communication between backend services.

gRPC supports four communication patterns

Traditional REST APIs typically follow a request-response model.

gRPC supports four communication patterns:

This flexibility makes gRPC useful for real-time applications, monitoring systems, event-driven architectures, and services that need continuous data exchange.

gRPC provides strongly typed service contracts

With REST, API contracts are often documented separately using tools such as OpenAPI.

With gRPC, the ".proto" file defines:

Service names.
RPC methods.
Request messages.
Response messages.
Field types.

The same contract can be shared between teams and used to generate client and server code.

This helps reduce inconsistencies between services and makes API evolution more structured.

When should you choose REST?

REST is still an excellent choice.

Consider REST when:

You're building public APIs for web or mobile applications.
Browser compatibility is important.
Human-readable JSON is useful.
You need straightforward integration with third-party services.
Your application mainly exposes conventional CRUD operations.

REST has a mature ecosystem and remains a practical choice for many applications.

When should you choose gRPC?

gRPC is particularly useful when:

Java microservices communicate internally.
Efficient serialization and transport matter.
You need client-side or server-side streaming.
Multiple services share strongly typed contracts.
Your architecture includes services written in different programming languages.

For internal service-to-service communication, gRPC can be a very effective alternative to REST.

Building gRPC microservices with Java and Micronaut

Micronaut provides a lightweight framework for building Java microservices.

Combined with gRPC and Protocol Buffers, it offers a practical foundation for implementing strongly typed service-to-service communication.

If you want to experiment with this approach without starting from scratch, I've created a project:

gRPC Micronaut Starter Kit

The starter kit provides a foundation for building Java gRPC microservices with Micronaut.

Explore the project:

"GitHub repository" (https://github.com/frekost/grpc-micronaut-starter-kit)
"Extended version on Gumroad" (https://frekost.gumroad.com/l/grpc2micronaut)

If you'd like to start with a practical introduction, you can also read my previous tutorial:

"Master Java gRPC with Micronaut: Your First Microservice in Minutes" (https://dev.to/frekost/master-java-grpc-with-micronaut-your-first-microservice-in-minutes-6l2)

Final thoughts

REST and gRPC are not technologies where one must always replace the other.

They solve different problems.

REST remains an excellent option for public APIs and browser-facing applications.

gRPC is a strong choice for efficient communication between backend services, especially when strongly typed contracts and streaming are important.

In many microservice architectures, both technologies can coexist.

What do you use for communication between Java microservices?

Do you prefer REST, gRPC, or a combination of both?

Share your experience in the comments. I'd love to hear your thoughts!

Master Java gRPC with Micronaut: Your First Microservice in Minutes

frekost — Thu, 22 Oct 2026 12:08:13 +0000

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 .proto files.
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!