Spring batch - pass values between reader and processor

Question

I have a requirement where I need to read values from an xls (where a column called netCreditAmount exists) and save the values in database. The requirement is to add the value of netCreditAmount from all the rows and then set this sum in database only for the first row in xls and remaining rows are inserted with their corresponding netCreditAmounts. How should I go ahead with the implemetation in Spring Batch. Normal reader, processor and writer are working fine but where exactly should i insert this implementation? Thanks!

Answer 1

So what is the problem? You need to setup your batch job step to use reader-processor-writer.

Reader has interface:

public interface ItemReader<T> {    
  T read();
}

Processor:

public interface ItemProcessor<I, O> {
  O process(I item);
}

So what you need to have same type provided by reader - T; and pass it to processor - I

stepBuilderFactory.get("myCoolStep")
            .<I, O>chunk(1)
            .reader(myReader)
            .processor(myProcessor)
            .writer(myWriter)
            .build();

Answer 2

Yo can solve this by adding additional tasklet. job flow can be like below

@Bean
    public Job myJob(JobBuilderFactory jobs) throws Exception {
        return jobs.get("myJob")
                .start(step1LoadAllData())  // This step will load all data in database excpet first row in xls
                .next(updateNetCreditAmountStep()) //// This step will be a tasklet. and will update total sum in first row. You can use database sql for sum for this 
                .build();           

    }

Tasklet will be something like below

@Component
public class updateNetCreditAmountTasklet implements Tasklet {  

    @Override
    public RepeatStatus execute(StepContribution stepContribution, ChunkContext chunkContext)
            throws Exception {
            Double sum = jdbctemplate.queryForObject("select sum(netCreditAmount) from XYZ", Double.class);
         // nouw update this some in database for first row 
        return null;
    }

}