java - Spring Batch如何在写入步骤之前处理数据列表

Question

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。但是我需要在写入数据之前处理 ItemReader 的整个结果。

例如，我正在从数据库行读取客户端:

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

但我想计算并写出有多少用户被激活，按订阅代码分组:

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

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

批量配置:

@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();
    }
}

主要应用:

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

如果我从您的评论中了解到您需要对激活的帐户进行总结，对吗？
您可以为正在处理的每个 Client 创建一个 Subscription，并使用 ItemWriterLister.afterWrite将上面创建的订阅项写入数据库。