Question

想象一下一个带有3个字段的Menu.java pojo：id，name和telephone。

我使用Spring Batch 3.我的处理器返回一个List。我想在文件中写下列表中每个对象的这些值。

如果菜单不是列表，那么这将是我的作家类：

@Bean(name="MyWriter")
@SphynxBatchStepScope
public FlatFileItemWriter<Menu> myWriter() String fileOutputName) {

    FlatFileItemWriter<Menu> writer = new FlatFileItemWriter<Menu>();   
    writer.setResource(new FileSystemResource("test.txt")));
    DelimitedLineAggregator<Menu> delLineAgg = new DelimitedLineAggregator<Menu>();
    delLineAgg.setDelimiter("          ");
    BeanWrapperFieldExtractor<Menu> fieldExtractor = new BeanWrapperFieldExtractor<Menu>();
    fieldExtractor.setNames(new String[] {"id", "name", "telephone"});
    delLineAgg.setFieldExtractor(fieldExtractor);
    writer.setLineAggregator(delLineAgg);
    writer.setHeaderCallback(header());
    writer.setFooterCallback(footer());
    writer.setEncoding("UTF-8");

    return writer;
}

但是，如果我想将这个类转换为使用List，我该怎么办呢？

我无法找到任何解决方案。只有这个：

Using an ItemWriter with List of Lists

但我不知道如何实现这一点。例如，在何处以及如何调用setDelegate方法。或者，当我需要将我的＆＃34; id＆＃34;，＆＃34; name＆＃34;，＆＃34;电话＆＃34;序列

请问，是否有人知道带有List的自定义Writer的代码示例？

提前致谢

Answer 1

你的作家将保持原样但被ListUnpackingItemWriter包裹。

// NOTE: this will now be the delegate used by the delegating writer.
// It will be injected to the delegating writer.
@Bean(name="MyDelegateWriter")
@SphynxBatchStepScope
public FlatFileItemWriter<Menu> myWriter(String fileOutputName) {

    FlatFileItemWriter<Menu> writer = new FlatFileItemWriter<Menu>();   
    writer.setResource(new FileSystemResource("test.txt")));
    DelimitedLineAggregator<Menu> delLineAgg = new DelimitedLineAggregator<Menu>();
    delLineAgg.setDelimiter("          ");
    BeanWrapperFieldExtractor<Menu> fieldExtractor = new BeanWrapperFieldExtractor<Menu>();
    fieldExtractor.setNames(new String[] {"id", "name", "telephone"});
    delLineAgg.setFieldExtractor(fieldExtractor);
    writer.setLineAggregator(delLineAgg);
    writer.setHeaderCallback(header());
    writer.setFooterCallback(footer());
    writer.setEncoding("UTF-8");

    return writer;
}

// NOTE: now this "MyWriter" will be used by your job
@Bean(name="MyWriter")
@SphynxBatchStepScope
public ListUnpackingItemWriter(@Qualifier("MyDelegateWriter") FlatFileItemWriter<Menu> delegate) {
    ListUnpackingItemWriter<List<Menu>> writer = new ListUnpackingItemWriter<>();
    writer.setDelegate(delegate);
    return writer;
}

Spring Batch 3自定义Writer列表

1 个答案: