Spring Batch多CSV合并任务完成但输出文件无数据求助

尝试使用Spring Batch读取resources/input目录下所有命名为user_*.csv的多份CSV文件，合并后写入resources/output/user.csv文件。执行过程无报错，但输出文件中没有数据，请求排查原因。

配置文件 #

@Configuration
@EnableBatchProcessing
public class BatchConfig {

    private static final Logger log = LoggerFactory.getLogger(BatchConfig.class);

    @Autowired
    private StepBuilderFactory stepBuilderFactory;

    @Autowired
    private JobBuilderFactory jobBuilderFactory;

    @Value(value = "classpath:input/user_*.csv")
    private Resource[] resources;

    @Bean
    public FlatFileItemReader<User> flatFileItemReader(){
        log.info("flatFileItemReader execution started");
        FlatFileItemReader<User> reader = new FlatFileItemReader<>();
        reader.setName("ReadMultipleCsv");
        reader.setLineMapper(lineMapper());
        log.info("flatFileItemReader execution completed");
        return reader;
    }

    private LineMapper<User> lineMapper(){
        DefaultLineMapper<User> lineMapper = new DefaultLineMapper<>();

        DelimitedLineTokenizer lineTokenizer = new DelimitedLineTokenizer();
        lineTokenizer.setDelimiter(",");
        lineTokenizer.setStrict(false);
        lineTokenizer.setNames(new String[] {"id","name","department","salary"});

        BeanWrapperFieldSetMapper<User> fieldSetMapper = new BeanWrapperFieldSetMapper<>();
        fieldSetMapper.setTargetType(User.class);

        lineMapper.setLineTokenizer(lineTokenizer);
        lineMapper.setFieldSetMapper(fieldSetMapper);
        return lineMapper;
    }

    @Bean
    public MultiResourceItemReader<User> multiResourceItemReader(){
        log.info("multiResourceItemReader() execution started");
        MultiResourceItemReader<User> reader = new MultiResourceItemReader<>();
        reader.setResources(resources);
        reader.setDelegate(flatFileItemReader());
        log.info("multiResourceItemReader() execution completed");
        return reader;
    }

    @Bean
    public FlatFileItemWriter<User> writer(){
        log.info("writer() execution started");
        FlatFileItemWriter<User> writer = new FlatFileItemWriter<>();
        writer.setResource(new ClassPathResource("output/user.csv"));
        writer.setAppendAllowed(true);

        DelimitedLineAggregator<User> delimitedLineAggregator = new DelimitedLineAggregator<>();
        delimitedLineAggregator.setDelimiter(",");
        BeanWrapperFieldExtractor<User> beanWrapperFieldExtractor = new BeanWrapperFieldExtractor<>();
        beanWrapperFieldExtractor.setNames(new String[] {"id","name","department","salary"});
        delimitedLineAggregator.setFieldExtractor(beanWrapperFieldExtractor);
        writer.setLineAggregator(delimitedLineAggregator);
        log.info("writer() execution completed");
        return writer;
    }

    @Bean
    public Step step(){
        return stepBuilderFactory.get("get-student").<User, User>chunk(5)
                .reader(multiResourceItemReader())
                .writer(writer()).build();
    }

    @Bean
    public Job job(){
        return jobBuilderFactory.get("process-student").incrementer(new RunIdIncrementer())
                .flow(step()).end().build();
    }
}

User实体类 #

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class User {

    private String id;
    private String name;
    private String department;
    private String salary;
}

执行日志 #

2022-08-22 16:40:06.295  INFO 17264 --- [           main] c.s.SpringBatchMultipleCsvToApplication  : Starting SpringBatchMultipleCsvToApplication using Java 1.8.0_121 on GBMLVVCSW3823 with PID 17264 (C:\Users\NavghS\Downloads\spring-batch-multiple-csv-to\spring-batch-multiple-csv-to\target\classes started by NavghS in C:\Users\NavghS\Downloads\spring-batch-multiple-csv-to\spring-batch-multiple-csv-to)

2022-08-22 16:40:06.300  INFO 17264 --- [           main] c.s.SpringBatchMultipleCsvToApplication  : No active profile set, falling back to 1 default profile: "default"

2022-08-22 16:40:08.999  INFO 17264 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)

2022-08-22 16:40:09.017  INFO 17264 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]

2022-08-22 16:40:09.018  INFO 17264 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.65]

2022-08-22 16:40:09.349  INFO 17264 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext

2022-08-22 16:40:09.350  INFO 17264 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2936 ms

2022-08-22 16:40:09.542  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : flatFileItemReader execution started

2022-08-22 16:40:09.554  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : flatFileItemReader execution completed

2022-08-22 16:40:09.559  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : multiResourceItemReader() execution started

2022-08-22 16:40:09.574  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : multiResourceItemReader() execution completed

2022-08-22 16:40:09.576  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : writer() execution started

2022-08-22 16:40:09.579  INFO 17264 --- [           main] com.shrikant.config.BatchConfig          : writer() execution completed

2022-08-22 16:40:10.299  INFO 17264 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''

2022-08-22 16:40:10.313  INFO 17264 --- [           main] c.s.SpringBatchMultipleCsvToApplication  : Started SpringBatchMultipleCsvToApplication in 5.205 seconds (JVM running for 6.176)

2022-08-22 16:40:10.316  INFO 17264 --- [           main] o.s.b.a.b.JobLauncherApplicationRunner   : Running default command line with: []

2022-08-22 16:40:10.317  WARN 17264 --- [           main] o.s.b.c.c.a.DefaultBatchConfigurer       : No datasource was provided...using a Map based JobRepository

2022-08-22 16:40:10.318  WARN 17264 --- [           main] o.s.b.c.c.a.DefaultBatchConfigurer       : No transaction manager was provided, using a ResourcelessTransactionManager

2022-08-22 16:40:10.339  INFO 17264 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : No TaskExecutor has been set, defaulting to synchronous executor.

2022-08-22 16:40:10.393  INFO 17264 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [FlowJob: [name=process-student]] launched with the following parameters: [{run.id=1}]

2022-08-22 16:40:10.612  INFO 17264 --- [           main] o.s.batch.core.job.SimpleStepHandler     : Executing step: [get-student]

2022-08-22 16:40:10.894  INFO 17264 --- [           main] o.s.batch.core.step.AbstractStep         : Step: [get-student] executed in 282ms

2022-08-22 16:40:10.907  INFO 17264 --- [           main] o.s.b.c.l.support.SimpleJobLauncher      : Job: [FlowJob: [name=process-student]] completed with the following parameters: [{run.id=1}] and the following status: [COMPLETED] in 344ms

排查关键点 #

• 验证资源加载情况：在multiResourceItemReader方法中添加日志打印resources.length，确认是否成功加载到目标CSV文件。如果长度为0，说明路径匹配失败，检查resources/input目录是否存在、文件名是否符合user_*.csv格式。
• 跳过CSV表头：如果输入CSV文件包含表头行，需在flatFileItemReader中设置reader.setLinesToSkip(1);，否则表头会被尝试解析为User对象，可能导致数据无法正确读取（即使strict=false不报错，也可能没有有效数据输出）。
• 修改写入资源路径：ClassPathResource指向的是类路径下的只读资源，运行时写入可能无法生效或写入到编译后的target/classes/output目录而非源码目录。建议改用FileSystemResource指定具体文件路径，比如：

  writer.setResource(new FileSystemResource("src/main/resources/output/user.csv"));
  

  或者检查target/classes/output/user.csv是否有数据。
• 添加数据读取验证：新增ItemProcessor打印读取到的User对象，确认是否真的读取到数据：

  @Bean
  public ItemProcessor<User, User> processor() {
      return user -> {
          log.info("读取到用户数据：{}", user);
          return user;
      };
  }
  

  然后在Step配置中添加.processor(processor())。

内容的提问来源于stack exchange，提问作者breakingcode