some base retryable grpc client

BaseRetryableGrpcClient.java

import com.google.gson.Gson;
import com.google.gson.stream.JsonReader;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;

import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Map;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
// grpc_config.json

{
  "methodConfig": [
    {
      "name": [
        { "service": "com.module.Service" }
      ],
      "timeout": "50s",
      "retryPolicy": {
        "maxAttempts" : 15,
        "initialBackoff" : "1s",
        "maxBackoff": "30s",
        "backoffMultiplier": 30,
        "retryableStatusCodes": [ "UNAVAILABLE" ]
      }
    }
  ]
}
*/

public interface BaseGrpcClient {
    /**
     * get retry config
     * @return {@link Map}
     * @throws IOException {@link IOException} some exception
     */
    default Map<String, ?> getRetryingServiceConfig() throws IOException {
        ResourceLoader resourceLoader = new DefaultResourceLoader();
        Resource resource = resourceLoader.getResource("grpc_config.json");
        return new Gson()
                .fromJson(
                        new JsonReader(new InputStreamReader(resource.getInputStream(), UTF_8)),
                        Map.class
                );
    }

    /**
     * build a channel
     * @param host {@link String}
     * @param port {@link Integer}
     * @return {@link ManagedChannel}
     */
    default ManagedChannel buildChannel(String host, Integer port) {
        var channelBuilder = ManagedChannelBuilder.forAddress(host, port).usePlaintext();
        try {
            channelBuilder.defaultServiceConfig(getRetryingServiceConfig()).enableRetry();
        } catch (Exception e){
            e.printStackTrace();
        }
        return channelBuilder.build();
    }
}