The library allows exposing GRPC services as REST-APIs using Connect protocol (with JSON messages) + GRPC Transcoding, without Envoy or any other proxy.

In essence, a service implementing the following protobuf definition:

syntax = "proto3"; package example; service ExampleService { rpc GetExample(GetExampleRequest) returns (GetExampleResponse) {} } message GetExampleRequest { string id = 1; } message GetExampleResponse { string name = 1; }

Is exposed to the clients as a REST API:

POST /example.ExampleService/GetExample HTTP/1.1 Content-Type: application/json { "id": "123" } HTTP/1.1 200 OK { "name": "example" }

It is compatible with Connect protocol clients (e.g., generated with Connect RPC protoc and buf plugins).

• Expose existing GRPC services as REST APIs without modifying the original service code alongside GRPC. GRPC services are used for internal communication, while REST APIs are used for external clients.
• Fully switch GRPC servers and clients to ConnectRPC protocol, while keeping the original GRPC service interfaces.
• Build from scratch using Connect RPC instead of GRPC, but still use the same service interfaces.

Dependency for Maven:

<dependency> <groupId>me.ivovk</groupId> <artifactId>connect-rpc-java-netty</artifactId> <version>${connect-rpc-java.version}</version> </dependency>

and for Gradle:

"me.ivovk:connect-rpc-java-netty:${connect-rpc-java.version}" 

The entry point that allows the server to be started is ConnectNettyServerBuilderclass:

import me.ivovk.connect_rpc_java.netty.ConnectNettyServerBuilder; // Your GRPC service(s) List<io.grpc.ServiceDefinition> grpcServices = List.of( ExampleServiceGrpc.getServiceDefinition() ); // Start the server var server = ConnectNettyServerBuilder .forServices(grpcServices) .port(8080) .build(); // Stop the server Runtime.getRuntime().addShutdownHook(new Thread(server::shutdown));

• Client-Server communication using Connect RPC protocol: link
• Starting both GRPC and Connect RPC servers: link

Run the following command to run Connect-RPC conformance tests:

make test-conformance-stable

Execution results are output to STDOUT. Diagnostic data from the server itself is written to the log file out/out.log.

• All incoming Connection-* headers are removed, as they aren’t allowed by GRPC.
• All outgoing grpc-* headers are removed.
• Original User-Agent request header is renamed to x-user-agent, user-agent is set to the in-process client's User Agent (grpc-java-inprocess/1.69.0), there is no way to disable it.

• Connect RPC website
• Connect RPC Java library
• Connect RPC Scala library
• Conformance Docker Image