Reading from streams instead of files in spring batch itemReader

Question

I am getting a csv file as a webservice call which needs to be laoded. Right now I am saving it in temp directory to provide it as setResource to Reader.

Is there a way to provide stream(byte[]) as is instead of saving the file first?

Answer 1

The method setResource of the ItemReader takes a org.springframework.core.io.Resource as a parameter. This class has a few out-of-the-box implementations, among which you can find org.springframework.core.io.InputStreamResource. This class' constructor takes a java.io.InputStream which can be implemented by java.io.ByteArrayInputStream.

So technically, yes you can consume a byte[] parameter in an ItemReader.

Now, for how to actually do that, here are a few ideas :

1. Create your own FlatFileItemReader (since CSV is a flat file) and make it implement StepExecutionListener

   public class CustomFlatFileItemReader extends FlatFileItemReader implements StepExecutionListener { }

2. Override the beforeStep method, do your webservice call within and save the result in a variable

   private byte[] stream;

   @Override public void beforeStep(StepExecution stepExecution) {

     // your webservice logic
     stream = yourWebservice.results();
   

   }

3. Override the setResource method to pass this stream as the actual resource.

   @Override public void setResource(Resource resource) {

    // Convert byte array to input stream
    InputStream is = new ByteArrayInputStream(stream);
   
    // Create springbatch input stream resource
    InputStreamResource res = new InputStreamResource(is);
   
    // Set resource
    super.setResource(res);
   

   }

Also, if you don't want to call your webservice within the ItemReader, you can simply store the byte array in the JobExecutionContext and get it in the beforeStep method with stepExecution.getJobExecution().getExecutionContext().get("key");