Building a Custom RPC Spring Starter: Architecture, Principles, and Code Walkthrough

Remote Procedure Call (RPC) enables a program to invoke methods on a remote server as if they were local calls; the article reviews its history, goals, and the main challenges such as service discovery, data representation, transmission, and method invocation.

The overall system consists of a registration center (Zookeeper) where service nodes register themselves, a client that discovers available nodes, serializes and compresses requests, sends them over Netty, and a server that decompresses, deserializes, and invokes the target method.

Service registration and discovery – The author uses Zookeeper persistent nodes for service definitions and temporary nodes for live instances. Example registration code: public void exportService(Service serviceResource) { String name = serviceResource.getName(); String uri = GSON.toJson(serviceResource); String servicePath = "rpc/" + name + "/service"; zkClient.createPersistent(servicePath, true); String uriPath = servicePath + "/" + uri; zkClient.createEphemeral(uriPath); } Discovery retrieves child nodes, decodes the JSON, and caches the list.

Client implementation – A dynamic proxy generated by ClientProxyFactory.getProxy intercepts method calls, builds an RpcRequest , selects a service instance via load‑balancing, serializes the request, compresses it, and sends it through netClient.sendRequest . The invocation handler extracts service name, method name, parameters, and version before dispatch.

Network transmission – The request bytes are sent over TCP using Netty. The article discusses TCP’s sticky‑packet problem and Netty’s three decoder options: FixedLengthFrameDecoder, LineBased/DelimiterBasedFrameDecoder, and LengthFieldBasedFrameDecoder.

Serialization and compression – Various serializers (Java Serializable, Protobuf, Kryo) and compressors (Gzip) are described. The MessageProtocol interface defines byte[] marshallingRequest(RpcRequest request) and RpcRequest unmarshallingRequest(byte[] data) , while the Compresser interface defines byte[] compress(byte[] bytes) and byte[] decompress(byte[] bytes) .

Server implementation – The server receives the request, decompresses and deserializes it, looks up the service object from serverRegister , and invokes the target method via reflection or Javassist‑generated proxy classes. Example handler code: public RpcResponse handleRequest(RpcRequest request) throws Exception { ServiceObject serviceObject = serverRegister.getServiceObject(request.getServiceName() + request.getGroup() + request.getVersion()); return invoke(serviceObject, request); }

The article also compares two server‑side proxy generation strategies: DefaultRpcReflectProcessor registers the original bean as the service object, while DefaultRpcJavassistProcessor creates a new proxy class with Javassist to wrap the bean, showing the generated proxy source for a sample HelloService interface.

Overall, the tutorial provides a comprehensive, hands‑on guide to building an RPC framework from scratch, covering architecture, service registry, dynamic proxies, serialization, compression, network handling, and server dispatch.