Spring Batch - write to 2 tables at once

Question

I have a Person object that has a list of addresses. My Spring Batch app converts Person JSON recors into Person POJOs and writes them to a database.

Ordinarily, I'd use JdbcBatchItemWriter but I see it is limited in writing to 2 seperate tables. I need to write to Person and Address table.

Hibernate could write this in one step but I don't see a simialr capability in Spring Bathc.

This SO question Multiple itemwriters in Spring batch suggests using a CompositeItemWriter but the issue with that is, I want my Address table to hold a column called Person_id to link an address back to Person. I won't be able to do that with 2 writes.

Any suggestions? Surely Batch caters for more complex writes

Answer 1

I see from the comment that you can't use an ORM or a service that persists a Person with its addresses. In this case, you can use a custom writer for that:

import java.util.List;

import javax.sql.DataSource;

import org.springframework.batch.item.ItemWriter;
import org.springframework.jdbc.core.JdbcTemplate;

public class PersonWriter implements ItemWriter<Person> {

    private JdbcTemplate jdbcTemplate;

    public PersonWriter(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Override
    public void write(List<? extends Person> items) {
        for (Person person : items) {
            jdbcTemplate.update("INSERT INTO Person ...");
            for (Address address : person.addresses) {
                jdbcTemplate.update("INSERT INTO Address ... where person_id = ?", person.getId()); 
            }
        }
    }
}

Another way to do it to delegate to two jdbc batch item writers:

import java.util.Collections;
import java.util.List;

import org.springframework.batch.item.ItemWriter;
import org.springframework.batch.item.database.JdbcBatchItemWriter;

public class PersonItemWriter implements ItemWriter<Person> {

    private JdbcBatchItemWriter<Person> personWriter;
    private JdbcBatchItemWriter<Address> addressWriter;

    public PersonItemWriter(JdbcBatchItemWriter<Person> personWriter, JdbcBatchItemWriter<Address> addressWriter) {
        this.personWriter = personWriter;
        this.addressWriter = addressWriter;
    }

    @Override
    public void write(List<? extends Person> persons) throws Exception {
        for (Person person : persons) {
            personWriter.write(Collections.singletonList(person));
            List<Address> addresses = person.getAddresses();
            for (Address address : addresses) {
                address.setPersonId(person.getId());
            }
            addressWriter.write(addresses);
        }
    }
}