Vert.x gRPC Protoc Plugin 2
The easiest way to start using Vert.x gRPC is to utilize its built-in code generator plugin. To do so,
one must define the protocol in the protobuffer
format as required by gRPC.
syntax = "proto3";
option java_multiple_files = true;
option java_package = "examples";
option java_outer_classname = "HelloWorldProto";
package helloworld;
// The greeting service definition.
service Greeter {
// 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;
}
This is a very simple example showing the single request, single response mode.
Compile the RPC definition
Using the definition above we need to compile it.
You can compile the proto file using the protoc
compiler if you like, or you can integrate it in your build.
If you’re using Apache Maven you need to add the plugin:
<plugin>
<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.6.1</version>
<configuration>
<protocArtifact>com.google.protobuf:protoc:${protoc.version}:exe:${os.detected.classifier}</protocArtifact>
<pluginId>grpc-java</pluginId>
<pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}</pluginArtifact>
<protocPlugins>
<protocPlugin>
<id>vertx-grpc-protoc-plugin2</id>
<groupId>io.vertx</groupId>
<artifactId>vertx-grpc-protoc-plugin2</artifactId>
<version>${stack.version}</version>
<mainClass>io.vertx.grpc.plugin.VertxGrpcGenerator</mainClass>
</protocPlugin>
</protocPlugins>
</configuration>
<executions>
<execution>
<id>compile</id>
<configuration>
<outputDirectory>${project.basedir}/src/main/java</outputDirectory>
<clearOutputDirectory>false</clearOutputDirectory>
</configuration>
<goals>
<goal>compile</goal>
<goal>compile-custom</goal>
</goals>
</execution>
</executions>
</plugin>
The ${os.detected.classifier}
property is used to make the build OS independant, on OSX it is replaced
by osx-x86_64 and so on. To use it you need to add the os-maven-plugin[https://github.com/trustin/os-maven-plugin]
in the build
section of your pom.xml
:
<build>
...
<extensions>
<extension>
<groupId>kr.motd.maven</groupId>
<artifactId>os-maven-plugin</artifactId>
<version>1.4.1.Final</version>
</extension>
</extensions>
...
</build>
This plugin will compile your proto files under src/main/proto
and make them available to your project.
If you’re using Gradle you need to add the plugin:
...
apply plugin: 'com.google.protobuf'
...
buildscript {
...
dependencies {
// ASSUMES GRADLE 2.12 OR HIGHER. Use plugin version 0.7.5 with earlier gradle versions
classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.0'
}
}
...
protobuf {
protoc {
artifact = 'com.google.protobuf:protoc:3.2.0'
}
plugins {
grpc {
artifact = "io.grpc:protoc-gen-grpc-java:1.25.0"
}
vertx {
artifact = "io.vertx:vertx-grpc-protoc-plugin2:${vertx.grpc.version}"
}
}
generateProtoTasks {
all()*.plugins {
grpc
vertx
}
}
}
This plugin will compile your proto files under build/generated/source/proto/main
and make them available to your project.
Generated RPC files
For each service definition, the plugin creates two Java RPC files.
For the Greeter
service:
-
examples/GreeterGrpcClient.java
-
examples/GreeterGrpcService.java
Besides the usual client/server generated code, these files contains service method constants:
public class GreeterGrpcClient {
public static final ServiceMethod<examples.HelloReply, examples.HelloRequest> SayHello = ServiceMethod.client(
ServiceName.create("helloworld", "Greeter"),
"SayHello",
GrpcMessageEncoder.encoder(),
GrpcMessageDecoder.decoder(examples.HelloReply.parser())
);
// ...
}
public class GreeterGrpcServer {
public static final ServiceMethod<examples.HelloRequest, examples.HelloReply> SayHello = ServiceMethod.server(
ServiceName.create("helloworld", "Greeter"),
"SayHello",
GrpcMessageEncoder.encoder(),
GrpcMessageDecoder.decoder(examples.HelloRequest.parser())
);
// ...
}
For each service method, a public static final ServiceMethod
is generated, these constants provide everything
Vert.x gRPC needs to know to interact with gRPC.
-
the service name:
/helloworld.Greeter
-
the service method name:
SayHello
-
the message decoder
-
the message encoder
They can be used to bind services or interact with a remote server.