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SOFARPC is a high-performance, high-extensibility, production-level Java RPC framework.
Lightweight REST for Java
Java language framework rpc source code implementation
A simple RPC framework based on Netty, ZooKeeper and Spring
JRPC is a lightweight Java RPC framework
Asynchronous RPC/REST library built on top of Java 8, Netty, HTTP/2, Thrift and gRPC