Add gRPC server and client samples with Spring Integration by cppwfs · Pull Request #377 · spring-projects/spring-integration-samples

cppwfs · 2026-02-12T16:05:23Z

Implement gRPC examples demonstrating Spring Integration's gRPC support for both server and client scenarios.

Server implementation:

Add GrpcInboundGateway with service routing for multiple RPC patterns
Implement unary RPC and server streaming streaming methods
Configure HelloWorldService with message routing based on service method headers

Client implementation:

Add GrpcOutboundGateway for unary and streaming response handling
Implement ApplicationRunner beans to demonstrate both communication patterns

rishiraj88 · 2026-02-12T22:42:49Z

Looks promising. Thanks.

artembilan

It also would be great to have tests for these new examples.
This way the samples project would serve a role of smoke tests for core project.
Thanks

artembilan · 2026-02-12T23:14:55Z

gradle.properties

 springBootVersion=4.1.0-SNAPSHOT
+protobufVersion=4.29.4
+protobufPluginVersion=0.9.4
+grpcVersion=1.78.0


That's not where we keep versions.
See ext block in the build.gradle.
And I guess we don't need protobufPluginVersion variable since it can simply go to the plugin definition itself.

artembilan · 2026-02-12T23:16:26Z

build.gradle

+
+	dependencies {
+		implementation 'org.springframework.boot:spring-boot-starter-integration'
+		implementation "org.springframework.integration:spring-integration-grpc:7.1.0-SNAPSHOT"


Why do we need explicit SI version here?
More over there is a dedicated variable in the ext block.

build.gradle

artembilan · 2026-02-12T23:17:45Z

build.gradle

+		//Test
+		testImplementation 'org.springframework.boot:spring-boot-starter-test'
+		testImplementation 'org.springframework.integration:spring-integration-test'
+		testRuntimeOnly 'org.junit.platform:junit-platform-launcher'


If we need this, then it probably should go to the common deps section for all the projects.

artembilan · 2026-02-12T23:18:22Z

build.gradle

+
+		//Test
+		testImplementation 'org.springframework.boot:spring-boot-starter-test'
+		testImplementation 'org.springframework.integration:spring-integration-test'


I think this one has to be in the common deps section.
If that is not the case, we should consider to improve the project.

artembilan · 2026-02-12T23:19:20Z

build.gradle

+
+	dependencies {
+		implementation 'org.springframework.boot:spring-boot-starter-integration'
+		implementation "org.springframework.integration:spring-integration-grpc:7.1.0-SNAPSHOT"


If you fix the server sample, I guess same has to be done for the client one, too.

artembilan · 2026-02-12T23:20:01Z

basic/grpc-server/src/main/resources/application.properties

@@ -0,0 +1 @@
+spring.grpc.server.port=9090


New line in the end of each file.
I believe there supposed to be an option in IntelliJ IDEA.

artembilan · 2026-02-12T23:24:45Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+			MessageChannel grpcInputChannelStreamResponse,
+			FluxMessageChannel grpcStreamOutputChannel) {
+		//TODO: Need advice, there has to be a better way than what I have below (or is this a bug in the
+		// GrpcOutboundGateway?


OK. Let's debug it together to see what is going on!

Looks like we don't need this anymore.
Plus, the gateway could be created from the Grpc DSL factory.

artembilan · 2026-02-17T17:37:17Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+			MessageChannel grpcInputChannelStreamResponse,
+			FluxMessageChannel grpcStreamOutputChannel) {
+		//TODO: Need advice, there has to be a better way than what I have below (or is this a bug in the
+		// GrpcOutboundGateway?


Looks like we don't need this anymore.
Plus, the gateway could be created from the Grpc DSL factory.

artembilan · 2026-02-17T17:38:34Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+ * @author Glenn Renfro
+ */
+@SpringBootTest(properties = {
+		"spring.main.web-application-type=none",


If we don't use web, then this looks suspicious.
As well as the next line.
Why do we need to override some bean?

artembilan · 2026-02-17T17:41:52Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+
+		@Bean
+		@Primary
+		public ApplicationRunner grpcClientStreamResponse() {


Are you sure we need to override these beans for test?
Feels like the sample is very complex, not something what users would expect coming here for beginner's knowledge

Please, elaborate why these bean overrides were not removed.

artembilan · 2026-02-17T17:43:01Z

.../grpc-server/src/test/java/org/springframework/integration/samples/grpc/GrpcServerTests.java

+/**
+ * @author Glenn Renfro
+ */
+@SpringBootTest(webEnvironment = WebEnvironment.NONE)


I'm still not sure what web is doing in these samples...

artembilan · 2026-02-17T17:46:00Z

gradle.properties

@@ -1,5 +1,6 @@
 version=7.1.0
 springBootVersion=4.1.0-SNAPSHOT
+protobufVersion=4.29.4


How that happened that grpcVersion has gone to ext, but not this?

artembilan · 2026-02-17T17:46:58Z

.../grpc-server/src/test/java/org/springframework/integration/samples/grpc/GrpcServerTests.java

+	@BeforeEach
+	void setUp() {
+		Object server = ReflectionTestUtils.getField(this.grpcServerLifecycle, "server");
+		this.grpcServerPort = ReflectionTestUtils.invokeMethod(server, "getPort");


I think something more convenient has to be Spring gRPC, rather than such a hack with reflection.

artembilan · 2026-02-18T14:19:51Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+	private static final Log LOG = LogFactory.getLog(ClientHelloWorldConfiguration.class);
+
+	/**
+	 * Creates a managed gRPC channel for communication with the server.


Why not imperative?
This is a method and this is a sample.
Why give readers of these samples a wrong impression about Spring code style and consistency?
Everything what we do here is for community and Spring newcomers.
Would be great to teach them a right lesson and don't overcomplicate the sample code scary impression reasons.

So, see also about those blank lines in method Javadocs.

artembilan · 2026-02-18T14:21:27Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+	 */
+	@Bean(destroyMethod = "shutdownNow")
+	ManagedChannel managedChannel(@Value("${grpc.server.host:localhost}") String host,
+			@Value("${grpc.server.port:9090}") int port) {


As we talked not one time: if method declaration is multi-line, a blank line before before method body.

I also wonder if there are some Spring gRPC auto-configuration for clients.
If there is really a reason to have our own ManagedChannel and those props with hard-coded defaults in the bean definition.

artembilan · 2026-02-18T14:22:50Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+	 *
+	 * @param grpcInputChannelStreamResponse the message channel for streaming response requests
+	 * @param grpcStreamOutputChannel channel that contains the responses
+	 * @param replyTimeout the time in seconds to await for the response.  Defaults to 1 second.


Why no consistency?
The previous example talks about milliseconds instead.

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

artembilan · 2026-02-18T14:29:42Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+					.doOnSubscribe(subscription -> {
+						HelloRequest request = HelloRequest.newBuilder().setName("Jack").build();
+						Message<?> requestMessage = MessageBuilder.withPayload(request).build();
+						grpcInputChannelStreamResponse.send(requestMessage);


When we do setReplyChannel(replyChannel), this should go outside of the Flux handling.
We can subscribe() and then send: exactly the way how it is recommended by Project Reactor.

artembilan · 2026-02-18T15:23:45Z

basic/grpc-client/src/main/proto/hello.proto

+
+package integration.grpc.hello;
+
+option java_package = "org.springframework.integration.grpc.proto";


We need to double check if these packages have a proper name.
Not sure if without a sample sub-package it is OK to deliver.

artembilan · 2026-02-18T15:25:04Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+
+		@Bean
+		@Primary
+		public ApplicationRunner grpcClientStreamResponse() {


Please, elaborate why these bean overrides were not removed.

artembilan · 2026-02-18T15:28:04Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+
+	@DynamicPropertySource
+	static void grpcServerProperties(DynamicPropertyRegistry registry) throws IOException {
+		mockGrpcServer = ServerBuilder.forPort(0)


That's not correct place to declare server instance.
Plus I wonder if it really should be a socket-based, but not InProcessServerBuilder, like we do in Spring Integration tests.
And another thought: I wonder if there is some Spring gRPC auto-configuration for testing to avoid a lot of boilerplate code like this to confuse end-users.

artembilan · 2026-02-18T15:31:05Z

basic/grpc-server/src/main/resources/application.properties

@@ -0,0 +1 @@
+spring.grpc.server.port=9090


Isn't that a default value?
Why do we need to declare this property here at all?
Probably mention Spring gRPC docs in the README to this sample should be enough.

artembilan · 2026-02-18T15:38:05Z

.../grpc-server/src/test/java/org/springframework/integration/samples/grpc/GrpcServerTests.java

+
+	@BeforeEach
+	void setUp() {
+		this.grpcServerPort = this.grpcServerLifecycle.getPort();


Doesn't look like we need the port as a property.
More over, I believe there should be some channel auto-configuration in Spring gRPC to avoid duplication.
Plus stubbing also can be done by Spring gRPC.
See their docs for more info.

Implement gRPC examples demonstrating Spring Integration's gRPC support for both server and client scenarios. Server implementation: - Add `GrpcInboundGateway` with service routing for multiple RPC patterns - Implement unary RPC and server streaming streaming methods - Configure HelloWorldService with message routing based on service method headers Client implementation: - Add `GrpcOutboundGateway` for unary and streaming response handling - Implement ApplicationRunner beans to demonstrate both communication patterns

- Removed POC experimental code

Replace manual channel/server setup in gRPC client and server samples with Spring gRPC's `GrpcChannelFactory` and in-process testing utilities to improve alignment with Spring conventions and reduce boilerplate. - Add `@EnableIntegration` to `ClientHelloWorldConfiguration` - Remove unused bidirectional and client-streaming RPC definitions from `hello.proto` in both client and server modules - Refactor `GrpcClientTests` to use an in-process gRPC server

artembilan

Thanks for the update!
Very close, but still there are some questions.

artembilan · 2026-03-02T16:33:03Z

basic/grpc-client/src/main/java/org/springframework/integration/samples/grpc/Application.java

+@SpringBootApplication
+public final class Application {
+
+	private Application() {


Was not addressed.

artembilan · 2026-03-02T16:34:43Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+	 */
+	@Bean
+	ManagedChannel managedChannel(GrpcChannelFactory factory) {
+		return factory.createChannel("local");


Isn't there an auto-configuration in Spring gRPC on the matter?

artembilan · 2026-03-02T16:35:14Z

basic/grpc-client/src/main/proto/hello.proto

+syntax = "proto3";
+import "types.proto";
+
+package integration.grpc.hello;


Do we need to revise this package as well?

artembilan · 2026-03-02T16:36:19Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+/**
+ * @author Glenn Renfro
+ */
+@SpringBootTest(properties = {"spring.grpc.server.enabled=false"})


Why do we do this instead of auto-configuration suggested by Spring gRPC?

artembilan · 2026-03-02T16:38:09Z

build.gradle

+
+	dependencies {
+		implementation 'org.springframework.boot:spring-boot-starter-integration'
+		implementation "org.springframework.integration:spring-integration-grpc:$springIntegrationVersion"


I don't think we need an explicit version for Spring Integration dependencies since we rely on Spring Boot management.

artembilan · 2026-03-02T16:58:57Z

basic/grpc-server/src/main/java/org/springframework/integration/samples/grpc/Application.java

+@SpringBootApplication
+public final class Application {
+
+	private Application() {


Also suspicious ctor.
How it happened here?
I never saw start.spring.io does that for us.

artembilan · 2026-03-02T17:01:07Z

.../grpc-client/src/test/java/org/springframework/integration/samples/grpc/GrpcClientTests.java

+
+		@Bean
+		GrpcInboundGateway helloWorldService() {
+			GrpcInboundGateway gateway = new GrpcInboundGateway(HelloWorldServiceGrpc.HelloWorldServiceImplBase.class);


I don't think that is what we want here in the test.
I believe just regular gRPC HelloWorldServiceImplBase implementation as a separate class in this test scope would be enough.
I mean that is fine that we verify Spring Integration server side, but that should not be a goal of the test in the sample for client side.

artembilan · 2026-03-02T17:03:44Z

...rg/springframework/integration/samples/grpc/configuration/ClientHelloWorldConfiguration.java

+		return flow -> flow
+				.handle(Grpc.outboundGateway(managedChannel, HelloWorldServiceGrpc.class)
+						.methodName("StreamSayHello"))
+				.channel(grpcStreamOutputChannel);


I see you do .setReplyChannel(grpcStreamOutputChannel) in the respective ApplicationRunner impl.
So, this one must not be here, but just fully similar to the grpcOutboundFlowSingleResponse configuration.

artembilan · 2026-03-02T17:06:05Z

basic/grpc-client/README.md

+
+```properties
+grpc.server.host=localhost
+grpc.server.port=9090


May it worth to have such an application.properties file in our sample?

artembilan · 2026-03-02T17:07:46Z

basic/grpc-server/README.md

+
+    $ gradlew :grpc-server:bootRun
+
+The server will start on port 9090 by default (configured in `application.properties`).


I see we do have such a file in the sample, but it is empty.
Should we add a respective property to let end-user to override it to something they want to play with?

cppwfs · 2026-03-02T17:55:04Z

I'm going to close this PR. I want to tackle it from a different angle from the current solution.

artembilan requested changes Feb 12, 2026

View reviewed changes

artembilan requested changes Feb 17, 2026

View reviewed changes

artembilan requested changes Feb 18, 2026

View reviewed changes

cppwfs added 4 commits March 2, 2026 09:40

Resolve Code Review issues

bfc1098

Resole code review comments

cb64227

- Removed POC experimental code

cppwfs force-pushed the SIS-add-grpc-samples branch from 8dbc2d6 to 25637a1 Compare March 2, 2026 15:13

artembilan requested changes Mar 2, 2026

View reviewed changes

cppwfs closed this Mar 2, 2026

		@@ -0,0 +1 @@
		spring.grpc.server.port=9090 No newline at end of file


		package integration.grpc.hello;

		option java_package = "org.springframework.integration.grpc.proto";


		$ gradlew :grpc-server:bootRun

		The server will start on port 9090 by default (configured in `application.properties`).

Conversation

cppwfs commented Feb 12, 2026

Uh oh!

rishiraj88 commented Feb 12, 2026

Uh oh!

artembilan left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

artembilan left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment