NotSerializableException with Spark

import org.springframework.stereotype.Service;
import java.io.Serializable;
@Service
class Job implements Serializable
{
    private Dataset<String> getPropIdValueEqualsDataset(final SparkSession sparkSession, final Dataset<Root> dataset, final String propId)
    {
        Map<String, Field> propFieldMap = Arrays.stream(FieldUtils.getAllFields(Root.class)).collect(Collectors.toMap(Field::getName, Function.identity()));
        Dataset<String> strDataset = dataset.flatMap(new FlatMapFunction<Root, String>() 
        {
            @Override
            public Iterator<String> call(Root root) throws Exception
            {
                List<String> list = new ArrayList<>();
                Field dataField = propFieldMap.get(propId);
                dataField.setAccessible(true);
                String dataFieldValue = (String)dataField.get(root);
                list.add(dataFieldValue);
                return list.iterator();
            }
        }, Encoders.bean(String.class));
        return strDataset;
    }
}

I am getting these two errors

1. org.apache.spark.SparkException: Job aborted due to stage failure: Task not serializable: java.io.NotSerializableException: java.lang.reflect.Field Serialization stack:
2. org.apache.spark.SparkException: Job aborted due to stage failure: Task not serializable: java.io.NotSerializableException: com.app.Job$$EnhancerBySpringCGLIB$$96d07abc

How do I fix this error?