How it Works

1. We can define the Size of Jobreader and Job Processor. In other words the no of records to be processed could be set using Jobreader and job processor
2. We dont have control over Jobwriter. Jobreader and JobProcessor honors chunk size

SimpleJobReader.java

import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.NonTransientResourceException;
import org.springframework.batch.item.ParseException;
import org.springframework.batch.item.UnexpectedInputException;
import org.springframework.stereotype.Component;
import java.util.Arrays;
import java.util.List;

@Component
public class SimpleJobReader implements ItemReader<Integer> {
    List<Integer> arrNum = Arrays.asList(1,2,3,4,5,6,7,8,9);
    int chunkSize = 3;
    int index = 0;

    @Override
    public Integer read() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException {
        System.out.println("Inside Job Reader");
        if(index < arrNum.size()){
            int num = arrNum.get(index);
            index++;
            return num;
        }
        index = 0;

        return null;
    }
}

SimpleJobProcessor.java

import org.springframework.batch.item.ItemProcessor;
import org.springframework.stereotype.Component;

@Component
public class SimpleJobProcessor implements ItemProcessor<Integer, Long> {
    @Override
    public Long process(Integer item) throws Exception {
        System.out.println("Inside Job Processor");
        return Long.valueOf(item);
    }
}

SimpleJobWriter.java

import org.springframework.batch.item.Chunk;
import org.springframework.batch.item.ItemWriter;
import org.springframework.stereotype.Component;

@Component
public class SimpleJobWriter implements ItemWriter<Long> {
    @Override
    public void write(Chunk<? extends Long> items) throws Exception {
        System.out.println("Inside Job Writer");
        items.getItems().forEach(System.out::println);
    }
}

SimpleJobWriter.java

@Configuration
public class BatchConfig {
    @Autowired
    ItemReader simpleJobReader;

    @Autowired
    ItemWriter simpleJobWriter;

    @Autowired
    ItemProcessor simpleJobProcessor;

    @Bean
    public Job job(JobRepository jobRepository, PlatformTransactionManager transactionManager) {
        return new JobBuilder("job", jobRepository)
                .incrementer(new RunIdIncrementer())
                .start(simpleTaskletStep(jobRepository, transactionManager))
                .next(simpleChunkStep(jobRepository, transactionManager))
                .build();
    }

    @Bean
    public Step simpleChunkStep(JobRepository jobRepository, PlatformTransactionManager transactionManager) {
        StepBuilder stepBuilderOne = new StepBuilder("Chunk Oriented Step", jobRepository);
        return stepBuilderOne
                .chunk(3, transactionManager)
                .reader(simpleJobReader)
                .processor(simpleJobProcessor)
                .writer(simpleJobWriter)
                .build();
    }

    @Bean
    public Step simpleTaskletStep(JobRepository jobRepository, PlatformTransactionManager transactionManager) {
        StepBuilder stepBuilderOne = new StepBuilder("Tasklet Oriented Step", jobRepository);
        return stepBuilderOne
                .tasklet(simpleTaskLet(), transactionManager)
                .build();
    }

    @Bean
    public Tasklet simpleTaskLet(){
        return (StepContribution contribution, ChunkContext chunkContext) -> {
            return RepeatStatus.FINISHED;
        };
    }
}

Output

Inside Job Reader
Inside Job Reader
Inside Job Reader
Inside Job Processor
Inside Job Processor
Inside Job Processor
Inside Job Writer
1
2
3
Inside Job Reader
Inside Job Reader
Inside Job Reader
Inside Job Processor
Inside Job Processor
Inside Job Processor
Inside Job Writer
4
5
6
Inside Job Reader
Inside Job Reader
Inside Job Reader
Inside Job Processor
Inside Job Processor
Inside Job Processor
Inside Job Writer
7
8
9
Inside Job Reader