Spring Batch中ItemWriter未执行时，如何验证数据库是否拉取到数据？

参考数据库读取打印列表的示例实现Spring Batch任务，目前能看到ItemReader和ItemWriter的初始化日志，但LoggingItemWriter的write方法未执行，想验证数据库是否成功拉取到数据。

我的Batch配置代码 #

@Configuration
@EnableBatchProcessing
public class BatchConfing {

    private static final String QUERY_FIND_STUDENTS =
            "select " +
                    "stu_info " +
                    "from myTable " +
                    "where status = '\"+PASS + \"" ;

    @Bean
    public ItemReader<StudentDTO> itemReader(DataSource dataSource) {
        System.out.println("Reached Reader");
        return new JdbcCursorItemReaderBuilder<StudentDTO>()
                .name("cursorItemReader")
                .dataSource(dataSource)
                .sql(QUERY_FIND_STUDENTS)
                .rowMapper(new BeanPropertyRowMapper<>(StudentDTO.class))
                .build();
    }

    @Bean
    public ItemWriter<StudentDTO> itemWriter(){
        System.out.println("I am in writer");
        return new LoggingItemWriter();
       /* return student -> {
            System.out.println("student.toString()");

        };*/
    }
    
    @Bean
    public JobExecutionListener listener() {
        return new ScheduelListener();
    }
    
    @Bean
    public Step stepA(@Qualifier("itemReader") ItemReader<StudentDTO> reader,
                      @Qualifier("itemWriter") ItemWriter<StudentDTO> writer,
                      StepBuilderFactory stepBuilderFactory) {
        return stepBuilderFactory.get("stepA")
                .<StudentDTO,StudentDTO>chunk(2)
                .reader(reader)
                .writer(writer)
                .build()
                ;
    }

    @Bean
    public Job jobA(@Qualifier("stepA") Step exampleJobStep,
                    JobBuilderFactory jobBuilderFactory){
        return jobBuilderFactory.get("jobA")
                .incrementer(new RunIdIncrementer())
                .listener(listener())
                .flow(exampleJobStep)
                .end()
                .build()
                ;
    }

}

LoggingItemWriter代码 #

public class LoggingItemWriter  implements ItemWriter<StudentDTO> {
    public LoggingItemWriter() {
        System.out.println("test LoggingItemWriter ");

    }

    private static final Logger LOGGER = LoggerFactory.getLogger(LoggingItemWriter.class);

    @Override
    public void write(List<? extends StudentDTO> list) throws Exception {
        LOGGER.info("Writing student info: {}", list);
        for (StudentDTO item : list) {
            System.out.println("test"+list);
        }

    }
}

验证数据库数据拉取的方法 #

• 直接调试Reader读取逻辑：在itemReader方法中临时添加手动读取测试，验证是否能获取数据：

  @Bean
  public ItemReader<StudentDTO> itemReader(DataSource dataSource) {
      System.out.println("Reached Reader");
      JdbcCursorItemReader<StudentDTO> reader = new JdbcCursorItemReaderBuilder<StudentDTO>()
              .name("cursorItemReader")
              .dataSource(dataSource)
              .sql(QUERY_FIND_STUDENTS)
              .rowMapper(new BeanPropertyRowMapper<>(StudentDTO.class))
              .build();
      // 临时测试读取逻辑
      try {
          reader.open(new ExecutionContext());
          StudentDTO dto;
          while ((dto = reader.read()) != null) {
              System.out.println("读取到数据：" + dto);
          }
          reader.close();
      } catch (Exception e) {
          e.printStackTrace();
      }
      return reader;
  }
  

• 修复SQL语句错误：当前SQL拼接存在语法问题，"where status = '\"+PASS + \""会生成无效SQL，改用参数化查询避免错误：

  private static final String QUERY_FIND_STUDENTS =
          "select stu_info from myTable where status = ?";
  
  // 构建Reader时设置参数
  return new JdbcCursorItemReaderBuilder<StudentDTO>()
          .name("cursorItemReader")
          .dataSource(dataSource)
          .sql(QUERY_FIND_STUDENTS)
          .parameterValues(PASS) // 传入PASS变量的实际值
          .rowMapper(new BeanPropertyRowMapper<>(StudentDTO.class))
          .build();
  

  SQL语法错误会导致查询无结果，Reader返回空数据，此时Writer的write方法不会被触发。
• 开启Spring Batch DEBUG日志：将日志级别调整为DEBUG，Spring Batch会打印Step执行统计、Reader读取记录数等详细信息，直接确认是否读取到数据。
• 临时替换Writer测试：把itemWriter中的返回逻辑换回你注释掉的匿名内部类，如果能打印内容，说明LoggingItemWriter的日志配置存在问题；如果仍无输出，说明Reader未读取到数据。

内容的提问来源于stack exchange，提问作者David