Contextual Data / Scoped Beans

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This section describes how you can store contextual / per request data.

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A Word of Warning

In grpc-java different steps in the message delivery / request process can and will run in different threads. This is not only but especially relevant for streaming calls. Avoid using ThreadLocals inside your ServerInterceptors and grpc service method implementations (in the entire grpc context). When it comes down to it, the preparation phase, every single message and the completion phase might run in different threads. If you wish to store data for the duration of the session, do so either using grpc’s Context or grpcRequest scoped beans.

grpcRequest Scope

This library adds a grpcRequest that works similar to spring web’s request scope. It is only valid for a single request.

First you define your bean with the @Scope annotation:

@Bean
@Scope(scopeName = "grpcRequest", proxyMode = ScopedProxyMode.TARGET_CLASS)
//@Scope(scopeName = GrpcRequestScope.GRPC_REQUEST_SCOPE_NAME, proxyMode = ScopedProxyMode.TARGET_CLASS)
ScopedBean myScopedBean() {
    return new ScopedBean();
}

The proxyMode = TARGET_CLASS is required unless you only use the bean inside another grpcRequest scoped bean. Please note that this proxyMode does not work with final classes or methods.

After that, you can use the bean as you are used to:

@Autowired
private ScopedBean myScopedBean;

@Override
public void grpcMethod(Request request, StreamObserver<Response> responseObserver) {
    responseObserver.onNext(myScopedBean.magic(request));
    responseObserver.onCompleted();
}

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