grpc全局异常处理（java版）

类似于spring mvc全局捕获异常，然后统一返回错误信息；我们尝试在Grpc中实现类似方案：

@GrpcGlobalServerInterceptor
public class GrpcGlobalInterceptor implements ServerInterceptor {

    @Override
    public <ReqT, RespT> Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> serverCall, Metadata metadata,
                                                      ServerCallHandler<ReqT, RespT> serverCallHandler) {
        Listener<ReqT> listener = serverCallHandler.startCall(serverCall, metadata);
        return new HandlingServerCallListener<ReqT, RespT>(listener, serverCall, metadata);
    }

    private class HandlingServerCallListener<ReqT, RespT> extends SimpleForwardingServerCallListener<ReqT> {

        private ServerCall<ReqT, RespT> serverCall;
        private Metadata                metadata;

        HandlingServerCallListener(Listener<ReqT> listener, ServerCall<ReqT, RespT> serverCall, Metadata metadata) {
            super(listener);
            this.serverCall = serverCall;
            this.metadata = metadata;
        }

        public void onHalfClose() {
            try {
                super.onHalfClose();
            } catch (RuntimeException e) {
                RespT resp = (RespT) AccountResponse.newBuilder()
                    .setCode(AccountNotFound.getCode())
                    .setMessage(e.getMessage())
                    .build();
                serverCall.sendHeaders(metadata);
                serverCall.sendMessage(resp);
                serverCall.close(Status.OK, metadata);
            }
        }
    }
}

非标准用法，慎重使用；建议通过 @ClientInterceptor 或 手动try-catch 在客户端拦截异常来进行处理；