在 Spring - "Writer must be open before it can be written to" 异常之外对 FlatFileItemWriter 进行单元测试

Question

我正在编写一个写入 CSV 文件的简单批处理，我想为此使用 Spring 批处理 FlatFileItemWriter，使用 Spring Boot 2.3。1.RELEASE .

我想对我的 writer 进行单元测试，以便确认它的配置是否正确。

代码很简单:

    public class CSVResultWriter implements ItemWriter<Project> {

    private final FlatFileItemWriter writer;

    public CSVResultWriter(String outputResource) {

      writer=new FlatFileItemWriterBuilder<Project>()
          .name("itemWriter")
          .resource(new FileSystemResource(outputResource))
          .lineAggregator(new PassThroughLineAggregator<>())
          .append(true)
          .build();

    }

   @Override
   public void write(List<? extends Project> items) throws Exception {
     writer.write(items);
   }
}

我正在编写一个没有 Spring 的简单单元测试，例如：

    File generatedCsvFile = new File(workingDir.toString() + File.separator + "outputData.csv");

    CSVResultWriter writer = new CSVResultWriter(generatedCsvFile.getAbsolutePath());

    Project sampleProject = Project.builder().name("sampleProject1").build();

    writer.write(List.of(sampleProject));

    assertThat(generatedCsvFile).exists();

但是测试失败说：

org.springframework.batch.item.WriterNotOpenException: Writer must be open before it can be written to

查看 Spring 源代码，我不明白如何让它工作。尝试编写项目时，Spring 做的第一件事是检查编写器已初始化：

https://github.com/spring-projects/spring-batch/blob/744d1834fe313204f06c0bcd0eedd472ab4af6be/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/AbstractFileItemWriter.java#L237

    @Override
    public void write(List<? extends T> items) throws Exception {
        if (!getOutputState().isInitialized()) {
            throw new WriterNotOpenException("Writer must be open before it can be written to");
        }
...

但是 OutputState 的构建方式并没有给出它已经启动的机会：

https://github.com/spring-projects/spring-batch/blob/744d1834fe313204f06c0bcd0eedd472ab4af6be/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/support/AbstractFileItemWriter.java#L363

    // Returns object representing state.
    protected OutputState getOutputState() {
        if (state == null) {
            File file;
            try {
                file = resource.getFile();
            }
            catch (IOException e) {
                throw new ItemStreamException("Could not convert resource to file: [" + resource + "]", e);
            }
            Assert.state(!file.exists() || file.canWrite(), "Resource is not writable: [" + resource + "]");
            state = new OutputState();
            state.setDeleteIfExists(shouldDeleteIfExists);
            state.setAppendAllowed(append);
            state.setEncoding(encoding);
        }
        return state;
    }

--> OutputState 中的 initialized 标志保留其默认值，即 false。

所以我有点困惑..我想当它由 Spring 管理时，一些神奇的事情发生了并且它起作用了。

我是不是遗漏了一些明显的东西，或者我们真的不能在 Spring 之外测试它吗？

Answer 1

FlatFileItemWriter 实现了 ItemStream 合同，在 Spring 批处理作业中使用时将自动兑现。

如果您想在 Spring 之外使用编写器，您需要手动调用这些方法 (open/update/close)。这在参考文档的 Item Stream 部分中提到：

Clients of an ItemReader that also implement ItemStream should call open before any calls
to read, in order to open any resources such as files or to obtain connections.
A similar restriction applies to an ItemWriter that implements ItemStream

在 Spring - "Writer must be open before it can be written to" 异常之外对 FlatFileItemWriter 进行单元测试

unit testing a FlatFileItemWriter outside of Spring - "Writer must be open before it can be written to" exception

java

spring-batch