How to read all files in a folder with spring-batch and MultiResourceItemReader?

Alternatively @Value annotation can be used to let ResourceArrayPropertyEditor convert string to Resource[].

@Bean
@StepScope
public ItemReader<String> reader(
        @Value("file:/myfolder/*.csv") Resource[] resources
) {
    MultiResourceItemReader<String> reader = new MultiResourceItemReader<>();
    reader.setResources(resources);
    reader.setDelegate(new FlatFileItemReader<>(..));
    return reader;
}

I think you should use a PathMatchingResourcePatternResolver.

Read multiple files from Absolute file path:

 @Bean
      public MultiResourceItemReader<POJO> multiResourceItemReader() {
        MultiResourceItemReader<POJO> resourceItemReader = new MultiResourceItemReader<POJO>();
            ClassLoader cl = this.getClass().getClassLoader();
            ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver(cl);

        Resource[] resources = resolver.getResources("file:" + filePath );
        resourceItemReader.setResources(resources);
        resourceItemReader.setDelegate(reader());
        return resourceItemReader;
      }

      @Bean
      public FlatFileItemReader<POJO> reader() {
        FlatFileItemReader<POJO> reader = new FlatFileItemReader<POJO>();
        reader.setLineMapper(new DefaultLineMapper() {{
          setLineTokenizer(new DelimitedLineTokenizer() {{
            setNames(new String[]{"id1", "POJO"});
          }});
          setFieldSetMapper(new BeanWrapperFieldSetMapper<POJO>() {{
            setTargetType(POJO.class);
          }});
        }});
        return reader;
      }

Use PathMatchingResourcePatternResolver like this.

@Bean
public ItemReader<String> reader() {
    Resource[] resources = null;
    ResourcePatternResolver patternResolver = new PathMatchingResourcePatternResolver();   
    try {
        resources = patternResolver.getResources("/myfolder/*.csv");
    } catch (IOException e) {
        e.printStackTrace();
    }
    MultiResourceItemReader<String> reader = new MultiResourceItemReader<>();
    reader.setResources(resources);
    reader.setDelegate(new FlatFileItemReader<>(..));
    return reader;
}