Pessimistic Lock for Jakarta Batch-compliant Batch Applications¶

This section shows an implementation example for pessimistic lock in a Jakarta Batch-compliant batch application. By implementing with reference to the examples shown below, the lock time can be reduced and the effect on other processes can be reduced.

Point

The ItemReader fetches only the primary key of the record to be processed.
Fetch the record for processing based on the master key in ItemProcessor and perform a pessimistic lock. For information on pessimistic lock using Universal DAO , see Pessimistic locking .

@Dependent
@Named
public class SampleReader extends AbstractItemReader {

    private DeferredEntityList<ProjectId> list;

    private Iterator<ProjectId> iterator;

    @Override
    public void open(Serializable checkpoint) throws Exception {

        // The acquisition process for search criteria is omitted

        list = (DeferredEntityList<ProjectId>) UniversalDao.defer()
                .findAllBySqlFile(ProjectId.class, "GET_ID", condition);
        iterator = list.iterator();
    }

    @Override
    public Object readItem() {
        if (iterator.hasNext()) {
            return iterator.next();
        }
        return null;
    }

    @Override
    public void close() throws Exception {
        list.close();
    }
}

@Dependent
@Named
public class SampleProcessor implements ItemProcessor {

    @Override
    public Object processItem(Object item) {
        final Project project =
                UniversalDao.findBySqlFile(Project.class, "FIND_BY_ID_WITH_LOCK", item);

        // Omitted for business operations

        return project;
    }
}

@Dependent
@Named
public class SampleWriter extends AbstractItemWriter {

    @Override
    public void writeItems(List<Object> items) {
        UniversalDao.batchUpdate(items);
    }
}