spring batch jpa with many to one relation - spring-data-jpa

Question

I'm trying to import csv file to populate my database.
City {
String name;
#ManyToOne
Country country;
String State;
double area;
}
Country {
String name;
String code;
}
Here is a csv record example:
city_name state country_name country_code area garbage_data
Toronto Ontario Canada CA 205.3 .....
I use spring data JPA to handle database transactions.
Here is my spring batch code:
#Bean
public FlatFileItemReader<City> reader() {
FlatFileItemReader<City> reader = new FlatFileItemReader<>();
reader.setResource(new ClassPathResource("Hotel-Cities.csv"));
reader.setLineMapper(new DefaultLineMapper<City>() {
{
setLineTokenizer(new DelimitedLineTokenizer() {
{
setIncludedFields(new int[]{0,1,2,3,4});
}
});
**//what to do here to map city that includes country?**
setFieldSetMapper(new BeanWrapperFieldSetMapper<City>() {
{
setTargetType(City.class);
}
});
}
});
return reader;
}
Since city has many-to-one relationship with country, where should I do something like dao.save(country);city.set(country); dao.save(city);
From what I learned, reader reads csv columns and map value to object, writer writes object to database. I still don't know how to resolve entity reference.
PS. I get type mismatch error when convert string to double, how to resolve it?