I tried to implement an example of Spring Boot Batch Processing from db to csv. The issue which I cannot solve is based on not sorting all values by id in csv file as well as showing column titles.

Here is the output in csv file. (First value is related with id)

3,9,2013-04-15,Japan,[email protected],Jard,MALE,Heino,87cdda81-45d0-451a-a62f-f8450eae1b64
2,23,1999-01-25,Panama,[email protected],Natala,FEMALE,Loynes,24be24e6-525f-42de-855d-52d4fef21608
6,9,2013-02-16,China,[email protected],Roseline,FEMALE,Cossans,06f70b0d-2c98-4f46-b933-528499ab91b3
4,8,2014-05-09,Indonesia,[email protected],Jilleen,FEMALE,Carlaw,c722e6d5-9024-49c5-80e0-c2555f1eb9cc
1,22,2000-08-15,China,[email protected],Ginnie,FEMALE,Spearing,fa26fa96-97d3-4e8e-856a-fdf07499e13e
5,22,2000-03-18,Indonesia,[email protected],Rainer,MALE,Gillino,5302a199-f313-4a24-9550-d643001d9faf

I want all values are sorted by id.

How can I do that?

Here is the batch configuration file shown below.

@Configuration // Informs Spring that this class contains configurations
@EnableBatchProcessing // Enables batch processing for the application
@RequiredArgsConstructor
public class BatchConfiguration {

    private final JobBuilderFactory jobBuilderFactory;
    private final StepBuilderFactory stepBuilderFactory;
    private final UserRepository userRepository;

    Date now = new Date(); // java.util.Date, NOT java.sql.Date or java.sql.Timestamp!
    String format1 = new SimpleDateFormat("yyyy-MM-dd'-'HH-mm-ss-SSS",Locale.forLanguageTag("tr-TR")).format(now);
    private Resource outputResource = new FileSystemResource("output/customers_"   format1   ".csv");

    @Bean
    public RepositoryItemReader<User> reader(){
        RepositoryItemReader<User> repositoryItemReader = new RepositoryItemReader<>();
        repositoryItemReader.setRepository(userRepository);
        repositoryItemReader.setMethodName("findAll");
        final HashMap<String, Sort.Direction> sorts = new HashMap<>();
        sorts.put("id", Sort.Direction.ASC);
        repositoryItemReader.setSort(sorts);
        return repositoryItemReader;
    }

    @Bean
    public FlatFileItemWriter<User> writer() {

        FlatFileItemWriter<User> writer = new FlatFileItemWriter<>();

        writer.setResource(outputResource);
        writer.setAppendAllowed(true);

        writer.setLineAggregator(new DelimitedLineAggregator<User>() {
            {
                setDelimiter(",");
                setFieldExtractor(new BeanWrapperFieldExtractor<User>() {
                    {
                        setNames(new String[]{"id", "age", "birthday", "country", "email", "firstName", "gender", "lastName", "personId"});
                    }
                });
            }
        });

        return writer;
    }

    @Bean
    public UserProcessor processor() {
        return new UserProcessor();
    }

    @Bean
    public UserJobExecutionNotificationListener stepExecutionListener() {
        return new UserJobExecutionNotificationListener(userRepository);
    }


    @Bean
    public UserStepCompleteNotificationListener jobExecutionListener() {
        return new UserStepCompleteNotificationListener();
    }

    @Bean
    public Step step1() {
        return stepBuilderFactory.get("csv-step").<User, User>chunk(10)
                .reader(reader())
                .processor(processor())
                .writer(writer())
                .listener(stepExecutionListener())
                .taskExecutor(taskExecutor())
                .build();
    }

    @Bean
    public Job runJob() {
        return jobBuilderFactory.get("importuserjob")
                .listener(jobExecutionListener())
                .flow(step1()).end().build();

    }

    @Bean
    public TaskExecutor taskExecutor() {
        SimpleAsyncTaskExecutor asyncTaskExecutor = new SimpleAsyncTaskExecutor();
        asyncTaskExecutor.setConcurrencyLimit(10);
        return asyncTaskExecutor;
    }
}

Here is the link of example : Link

CodePudding user response：

After I added FlatFileHeaderCallback into FlatFileItemWriter, I fixed the issue.

Here is the code snippets shown below.

 writer.setHeaderCallback(new FlatFileHeaderCallback() {
            @Override
            public void writeHeader(Writer writer) throws IOException {
                for(int i=0;i<headers.length;i  ){
                    if(i!=headers.length-1)
                        writer.append(headers[i]   ",");
                    else
                        writer.append(headers[i]);
                }
            }
        });