Writing List of Items using JdbcBatchItemWriter - list

Question

Currently i am using JpaItemWriter to write the list of objects as below which is working fine.
Now i want to change the JpaItemWriter to JdbcBatchItemWriter due to performance issue.
public class MyItemWriter implements ItemWriter<List<MyDomainObject>> {
#Override
public void write(List<? extends Lists<MyDomainObject>> items) {
JpaItemWriter<MyDomainObject> writer = new JpaItemWriter<>();
for(List<MyDomainObject> o : items)
{
writer.write(o);
}
}
}
Suggest a sample snippets which uses the JdbcBatchItemWriter to write the List of objects will helps. Tried using the ItemSqlParameterSourceProvider it did't help ending up in org.springframework.dao.InvalidDataAccessApiUsageException: No value supplied for the SQL parameter exception

Answer 1

You example is not correct. You are creating a JpaItemWriter in the write method, so a new instance is created on each call to write. This is probably the cause of your performance issue.
More importantly, lifecycle methods of the delegate writer (open/update/close) will not be honored (it is not the case for JpaItemWriter which does not implement ItemStream but this would be a problem if the delegate is an item stream). Your MyItemWriter implementation should be something like:
public class MyItemWriter implements ItemWriter<List<MyDomainObject>> {
private JpaItemWriter jpaItemWriter;
public MyItemWriter(JpaItemWriter jpaItemWriter) {
this. jpaItemWriter = jpaItemWriter;
}
#Override
public void write(List<? extends Lists<MyDomainObject>> items) {
for(List<MyDomainObject> o : items) {
this. jpaItemWriter.write(o);
}
}
}
Now if you want to use the JdbcBatchItemWriter to write a list of lists, see Spring Batch - Using an ItemWriter with List of Lists.
Edit: Added a sample code of how to set the delegate as requested in comments:
#Bean
public ListUnpackingItemWriter<T> itemWriter() {
JdbcBatchItemWriter<T> jdbcBatchItemWriter = null; // configure your jdbcBatchItemWriter
ListUnpackingItemWriter<T> listUnpackingItemWriter = new ListUnpackingItemWriter<>();
listUnpackingItemWriter.setDelegate(jdbcBatchItemWriter);
return listUnpackingItemWriter;
}