java.lang.IllegalStateException: InputStream 已被读取 - 如果需要多次读取流，请不要使用 InputStreamResource

Question

我正在尝试从 aws s3 存储桶中读取文件并将其设置为我的 spring 批处理读取器类中的资源。当我在 aws lambda 函数上测试应用程序时，出现以下错误。任何建议专家？

    Caused by: java.lang.IllegalStateException: InputStream has already been read - do not use InputStreamResource if a stream needs to be read multiple times
    at org.springframework.core.io.InputStreamResource.getInputStream(InputStreamResource.java:97) ~[task/:na]
    at org.springframework.batch.item.file.DefaultBufferedReaderFactory.create(DefaultBufferedReaderFactory.java:34) ~[task/:na]
    at org.springframework.batch.item.file.FlatFileItemReader.doOpen(FlatFileItemReader.java:266) ~[task/:na]
    at org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.open(AbstractItemCountingItemStreamItemReader.java:146) ~[task/:na]

Class to read from s3 bucket
@Service
public class S3BucketProcessing {
private static final AmazonS3 s3 = AmazonS3ClientBuilder.standard().build();

public InputStreamResource readFile() throws IOException{

   String bucketName = "mybuckey";
   String key = "File.txt";

   S3Object object = s3.getObject(new GetObjectRequest(bucketName, key));    

   return new InputStreamResource(object.getObjectContent());

}

Spring批处理阅读器类

    @Component
public class MyReader extends FlatFileItemReader<MyEntity> {

    MyLineMapper mapper;
    MyTokenizer tokenizer;
    S3BucketProcessing s3BucketProcessing;

    @Autowired
    public MyReader(MyTokenizer tokenizer, MyLineMapper mapper, S3BucketProcessing s3BucketProcessing) throws Exception{
        LOG.info("CardCustomerNotificationReader constructor");
        this.mapper = mapper;
        this.tokenizer = tokenizer;
        this.s3BucketProcessing= s3BucketProcessing;
        this.setResource(s3BucketProcessing.readFile());
        mapper.setLineTokenizer(tokenizer);
        this.setLineMapper(mapper);
    }
}

Answer 1

文档建议使用 ByteArrayResource 将内容缓存在内存中，而不是 InputStreamResource。

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/core/io/InputStreamResource.html

只需像这样更改返回部分：

//As suggested by berzerk
byte[] content = IOUtils.toByteArray(object.getObjectContent()); 

//Then
return new ByteArrayResource( content );