Spring Batch如何在寫入步驟之前處理數據列表

Question

我試圖從數據庫中讀取客戶端數據並將處理后的數據寫入平面文件。 但是我需要在寫入數據之前處理ItemReader整個結果。

例如，我從數據庫行讀取Client：

public class Client {
    private String id;
    private String subscriptionCode;
    private Boolean activated;
}

但是我想要計算並編寫由subscriptionCode分組激活的用戶數：

public class Subscription {
    private String subscriptionCode;
    private Integer activatedUserCount;
}

我不知道如何使用ItemReader / ItemProcessor / ItemWriter執行該操作，你能幫幫我嗎？

BatchConfiguration：

@CommonsLog
@Configuration
@EnableBatchProcessing
@EnableAutoConfiguration
public class BatchConfiguration {

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Bean
    public Step step1() {
        return stepBuilderFactory.get("step1")
                .<Client, Client> chunk(1000)
                .reader(new ListItemReader<Client>(new ArrayList<Client>() { // Just for test
                    {
                        add(Client.builder().id("1").subscriptionCode("AA").activated(true).build());
                        add(Client.builder().id("2").subscriptionCode("BB").activated(true).build());
                        add(Client.builder().id("3").subscriptionCode("AA").activated(false).build());
                        add(Client.builder().id("4").subscriptionCode("AA").activated(true).build());
                    }
                }))
                .processor(new ItemProcessor<Client, Client>() {
                    public Client process(Client item) throws Exception {
                        log.info(item);
                        return item;
                    }
                })
                .writer(new ItemWriter<Client>() {
                    public void write(List<? extends Client> items) throws Exception {
                        // Only here I can use List of Client
                        // How can I process this list before to fill Subscription objects ?
                    }
                })
                .build();
    }

    @Bean
    public Job job1(Step step1) throws Exception {
        return jobBuilderFactory.get("job1").incrementer(new RunIdIncrementer()).start(step1).build();
    }
}

主要應用：

public class App {
    public static void main(String[] args) throws JobExecutionAlreadyRunningException, JobRestartException, JobInstanceAlreadyCompleteException, JobParametersInvalidException {
        System.exit(SpringApplication.exit(SpringApplication.run(BatchConfiguration.class, args)));
    }
}

Answer 1

如果我從您的評論中了解到您需要對激活的帳戶進行總結，對吧？
您可以為正在處理的每個Client創建Subscription ，並使用ItemWriterLister.afterWrite將上面創建的Subscription項寫入數據庫。

Answer 2

我發現了一個基於ItemProcessor的解決方案：

@Bean
public Step step1() {
  return stepBuilderFactory.get("step1")
      .<Client, Subscription> chunk(1000)
      .reader(new ListItemReader<Client>(new ArrayList<Client>() {
        {
          add(Client.builder().id("1").subscriptionCode("AA").activated(true).build());
          add(Client.builder().id("2").subscriptionCode("BB").activated(true).build());
          add(Client.builder().id("3").subscriptionCode("AA").activated(false).build());
          add(Client.builder().id("4").subscriptionCode("AA").activated(true).build());
        }
      }))
      .processor(new ItemProcessor<Client, Subscription>() {
        private List<Subscription> subscriptions;

        public Subscription process(Client item) throws Exception {
          for (Subscription s : subscriptions) { // try to retrieve existing element
            if (s.getSubscriptionCode().equals(item.getSubscriptionCode())) { // element found
              if(item.getActivated()) {
                s.getActivatedUserCount().incrementAndGet(); // increment user count
                log.info("Incremented subscription : " + s);
              }                             
              return null; // existing element -> skip
            }
          }
          // Create new Subscription
          Subscription subscription = Subscription.builder().subscriptionCode(item.getSubscriptionCode()).activatedUserCount(new AtomicInteger(1)).build();
          subscriptions.add(subscription);
          log.info("New subscription : " + subscription);
          return subscription;
        }

        @BeforeStep
        public void initList() {
          subscriptions = Collections.synchronizedList(new ArrayList<Subscription>());
        }

        @AfterStep
        public void clearList() {
          subscriptions.clear();
        }
      })
      .writer(new ItemWriter<Subscription>() {                  
        public void write(List<? extends Subscription> items) throws Exception {
          log.info(items);
          // do write stuff
        }                   
      })
      .build();
}

但我必須在ItemProcessor維護第二個Subscription列表（我不知道線程安全且高效嗎？）。 您對此解決方案有何看法？