Spring Batch如何在写入步骤之前处理数据列表 [英] Spring Batch how to process list of data before write in a Step

问题描述

我正在尝试从数据库中读取客户端数据并将处理后的数据写入平面文件。
但我需要在写入数据之前处理 ItemReader 的整个结果。

I am trying to read client data from database and write processed data to a flat file. But I need to process whole result of the ItemReader before write data.

例如，我从数据库行读取客户端：

For example, I am reading Client from database rows :

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

但是我想要计算并写下按subscriptionCode分组激活的用户数：

But I want to count and write how many user are activated grouped by subscriptionCode :

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

我不知道如何使用执行此操作ItemReader / ItemProcessor / ItemWriter ，你能帮助我吗？

I don't know how to perform that using ItemReader/ItemProcessor/ItemWriter, can you help me ?

BatchConfiguration：

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();
    }
}

主要申请：

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

推荐答案

我找到了一个基于 ItemProcessor 的解决方案：

I found a solution based on ItemProcessor :

@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();
}

但我必须维持第二个订阅列入 ItemProcessor （我不知道线程是否安全且高效？）。您对此解决方案有何看法？

But I have to maintain a second Subscription List into ItemProcessor (I don't know if is thread safe and efficient ?). What do you think about this solution ?

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