DruidCoordinatorConfig.java

public class DruidCoordinatorConfig
{
 //
 // skipping other exisiting configs
 //

 /* 
 I was thinking JsonConfigProvider.bind("druid.coordinator", DruidCoordinatorConfig.class)
 could magically recursively deserialize DruidCoordinatorHadoopMergeConfig using properties
 starting with "druid.coordinator.hadoopMerge".
 */
 @JsonProperty("hadoopMerge")
 private DruidCoordinatorHadoopMergeConfig coordinatorHadoopMergeConfig;
 
}

DruidCoordinatorHadoopMergeConfig.java

public class DruidCoordinatorHadoopMergeConfig
{

  @JsonProperty("on")
  private boolean on = false;

  @JsonProperty("keepGap")
  private boolean keepGap = false;

  @JsonProperty("tuningConfig")
  private Map<String, Object> tuningConfig;

  public boolean isOn()
  {
    return on;
  }

  public boolean isKeepGap()
  {
    return keepGap;
  }

  public Map<String, Object> getTuningConfig()
  {
    return tuningConfig;
  }
}