Spring-Batch: Item writer for Parent-Child relationship - spring-batch

Question

I have written a item processor which returns the list of Objects. This object needs to be split into 2 data base table (One parent and a child). One header row and for this corresponding header ID we have child rows associated in child table. I have used ListUnpackingItemWriter example to solve list problem. I have used CompositeItemWriter to split the result into 2 writer, Now I need to split each one for header and child table. Now each writer has same number of rows. IS there a better way to do it? Solve both Table Primary key problem. I need example write custom item writer which does validation before insert. Thanking you in advance.
Below is the code
public JdbcBatchItemWriter<T> myWriter() {
JdbcBatchItemWriter<T> myWriter = new JdbcBatchItemWriter<T>();
myWriter.setItemSqlParameterSourceProvider(new BeanPropertyItemSqlParameterSourceProvider<T>());
myWriter.setSql("INSERT INTO Parent table( colums) values ( values )");
myWriter.setDataSource(dataSource);
myWriter.afterPropertiesSet();
return myWriter;
}
public JdbcBatchItemWriter<T> myOtherWriter() {
JdbcBatchItemWriter<T> myWriter = new JdbcBatchItemWriter<T>(); 1
myWriter.setItemSqlParameterSourceProvider(new BeanPropertyItemSqlParameterSourceProvider<T>());
myWriter.setSql("INSERT INTO child table( colums) values ( values )");
myWriter.setDataSource(dataSource);
myWriter.afterPropertiesSet();
return myWriter;
}
public CompositeItemWriter<T> compositeItemWriter() {
CompositeItemWriter<T> writer = new CompositeItemWriter<T>();
writer.setDelegates(Arrays.asList(myWriter(),myOtherWriter()));
return writer;
}
```

Answer 1

If the composite writer does not work for you, then can you use a custom writer, something like:
import java.util.List;
import javax.sql.DataSource;
import org.springframework.batch.item.ItemWriter;
import org.springframework.jdbc.core.JdbcTemplate;
public class MyParentChildWriter implements ItemWriter<Object> {
private JdbcTemplate jdbcTemplate;
public MyParentChildWriter(DataSource dataSource) {
this.jdbcTemplate = new JdbcTemplate(dataSource);
}
#Override
public void write(List<?> items) {
for (Object item : items) {
// get parent/child values from item and use them in the query as needed
jdbcTemplate.update("INSERT INTO Parent table( colums) values ( values )");
jdbcTemplate.update("INSERT INTO child table( colums) values ( values )");
}
}
}
Note that all update statements will be executed in a single transaction as explained in the Chunk-oriented Processing section.