proto-java

Introduction

This project offers an alternative way of working with gRPC in Java. Rather than defining the Protocol Buffer files specification in a .proto file, we can now define it in Java using annotations.

Modules

• proto-java-annotation
• proto-java-default-gen
• proto-java-plugin

proto-java-annotation

This module automatically converts Java POJOs and interfaces to .proto files during time.

Examples

Simply add custom annotation @ProtoMessage and @ProtoField annotation to the POJO.

@ProtoMessage(protoName = "helloworld", protoPackage = "example.helloworld")
public class HelloReply {
    @ProtoField(tag = 1) private String name;
}

@ProtoMessage(protoName = "helloworld", protoPackage = "example.helloworld")
public class HelloRequest {
    @ProtoField(tag = 1) private String message;
    @ProtoField(tag = 2) private Integer id;
}

And add custom annotation @ProtoService and @ProtoMethod annotation to an interface.

@ProtoService(protoName = "helloworld", protoPackage = "example.helloworld")
public interface Greeter {
    @ProtoMethod CompletableFuture<HelloReply> sayHello(HelloRequest request);
}

A .proto file will be generated in target/classes or target/test-classes

proto-java-default-gen

If protoc binary is already available in the $PATH, this module automatically generate gRPC client and server implementation of interfaces annotated with @ProtoService.

How to apply

Simply add the module as dependency

    <dependency>
        <groupId>io.github.lwlee2608</groupId>
        <artifactId>proto-java-default-gen</artifactId>
        <version>VERSION</version>
    </dependency>

Example Server

    Server server = ServerBuilder
        .forPort(8080)
        .addService(new HelloworldProto.GreeterService.GreeterServerImpl(new Greeter() {
            @Override
            public CompletableFuture<HelloReply> sayHello(HelloRequest request) {
                return CompletableFuture.completedFuture(new HelloReply().setName(request.getMessage() + " World"));
            }
        }))
        .build();

Example Client

    Greeter client = new HelloworldProto.GreeterService.GreeterClientImpl(channel, CallOptions.DEFAULT);
    client.sayHelloFuture(new HelloRequest().setMessage("Hello").setId(1));

View the full example here

Supported Method

Asynchronous Type	Project	Supported
StreamObserver	io.grpc	✔️
CompletableFuture	JDK	✔️

proto-java-plugin

If protoc binary is not available in $PATH, use this maven-plugin to automatically download it

How to apply

Make sure execution phase is set to process-sources

    <plugin>
        <groupId>io.github.lwlee2608</groupId>
        <artifactId>proto-java-plugin</artifactId>
        <version>VERSION</version>
        <executions>
            <execution>
                <id>download-protoc-binary</id>
                <phase>process-sources</phase>
                <goals>
                    <goal>download</goal>
                </goals>
            </execution>
        </executions>
    </plugin>