protoc-gen-spring-webflux

gRPC to JSON handler generator protoc plugin for Spring WebFlux inspired by grpc-gateway.

The protoc-gen-spring-webflux is a plugin of the Google protocol buffers compiler protoc. It reads protobuf service definitions and generates Spring WebFlux HTTP server classes which translates RESTful HTTP API into gRPC. This server is generated according to the google.api.http annotations in your service definitions.

Uses an external HTTP server separately from the gRPC server to convert Http requests to gRPC calls.

Usage

1. Define your gRPC service using protocol buffers.

syntax = "proto3";

package example.demo;

// messages...

service EchoService {

    rpc GetEcho(EchoRequest) returns (EchoResponse) {
    }

    rpc CreateEcho(CreateEchoRequest) returns (CreateEchoResponse) {
    }
}

2. Add a google.api.http annotation to your .proto file for HTTP API.

syntax = "proto3";

package example.demo;
+import "google/api/annotations.proto";

// messages...

service EchoService {

    rpc GetEcho(EchoRequest) returns (EchoResponse) {
+        option (google.api.http) = {
+            get: "/echo/{echo}"
+        };
    }

    rpc CreateEcho(CreateEchoRequest) returns (CreateEchoResponse) {
+        option (google.api.http) = {
+              post: "/echo"
+              body: "*"
+        };
    }
}

3. Generate routing handler class using protoc-gen-spring-webflux

3-a. Use protoc plugin on Linux or OSX

• When building in a Linux or OSX environment, build with the protoc plugin.

# build.gradle

protobuf {
    protoc {
        // ...
    }

    plugins {
        // ...
+       webflux {
+           artifact = 'io.github.protobuf-x:protoc-gen-spring-webflux:${PROTOC_GEN_SPRING_WEBFLUX_VERSION}'
+       }
    }

    generateProtoTasks {
        all()*.plugins {
            // ...
+           webflux {}
        }
    }
}

3-b. Use protoc command

• Since the protobuf plugin for windows is not supported, please execute the protoc command if you need to build on windows.

protoc -I. \
    --spring-webflux_out=. \
     example.proto

Download the latest binaries from Maven Central Repository.

4. Write an routing of the Spring WebFlux Handler server.

@Configuration
class HandlerServerConfg {
    @Bean
    ExampleHandlers.EchoServiceHandler exampleHandlers() {
        ManagedChannel channel = ManagedChannelBuilder.forAddress(/*...*/)
                .usePlaintext()
                .build();
        EchoServiceGrpc.EchoServiceStub stub = EchoServiceGrpc.newStub(channel);

        // ExampleHandlers is a class generated by protoc-gen-spring-webflux
        return EchoServiceRest.newGrpcProxyBuilder()
                .setStub(stub)
                .setIncludeHeaders(Collections.singletonList("Authorization"))
                .build();
    }

    @Bean
    RouterFunction<ServerResponse> routing(ExampleHandlers.EchoServiceHandler handler) {
        return RouterFunctions.route()
                // Use the handleAll method to route everything to the generated Handler.
                .add(handler.allRoutes())
                // Handler can be routed individually by using the generated method.
                .GET("/echo/{id}", handler::getEcho)
                .POST("/echo", handler::createEcho)
                .build();
    }
}

Missing Features Shortlist

• Streams not supported.
• Custom patterns not supported.
• Variables not supported.
• Not supporting * and ** in path.

License

(The MIT License)

Copyright (c) 2020 @disc99