Spring batch read file one by one. File content is not constant - spring

Question

MultiResourceItemReader reads all files sequentially.
I want once one file read completely, it should call processor/writer.it should not read next file.
Since file content is not constant, i can't go with chunk size.
Any idea on chunk policy to decide end of file content?

Answer 1

I think you should write a step which read/process/write only one file with a "single file item reader" (like FlatFileItemReader). And repeat the step while there are files remainig.
Spring batch gives you a feature to do so : conditional flows and in particular the programmatic flow decision which gives you a smart way to decide when to stop a loop between steps (when there is not file any more)
And since you will not be able to give a constant input file name to your reader, you should also have a look at Late binding section.
Hope this will be enough to help you. Please, make comments if you need more details.

Answer 2

Using MultiResourceItemReader, assigning multiple file reasources.
Using custom file reader as delegate, reading a file completely
For reading file completely, come up with a logic
#Bean
public MultiResourceItemReader<SimpleFileBean> simpleReader()
{
Resource[] resourceList = getFileResources();
if(resourceList == null) {
System.out.println("No input files available");
}
MultiResourceItemReader<SimpleFileBean> resourceItemReader = new MultiResourceItemReader<SimpleFileBean>();
resourceItemReader.setResources(resourceList);
resourceItemReader.setDelegate(simpleFileReader());
return resourceItemReader;
}
#Bean
SimpleInboundReader simpleFileReader() {
return new SimpleInboundReader(customSimpleFileReader());
}
#Bean
public FlatFileItemReader customSimpleFileReader() {
return new FlatFileItemReaderBuilder()
.name("customFileItemReader")
.lineMapper(new PassThroughLineMapper())
.build();
}
public class SimpleInboundReader implements ResourceAwareItemReaderItemStream{
private Object currentItem = null;
private FileModel fileModel = null;
private String fileName = null;
private boolean fileRead = false;
private ResourceAwareItemReaderItemStream<String> delegate;
public SimpleInboundReader(ResourceAwareItemReaderItemStream<String> delegate) {
this.delegate = delegate;
}
#Override
public void open(ExecutionContext executionContext) throws ItemStreamException {
delegate.open(executionContext);
}
#Override
public void update(ExecutionContext executionContext) throws ItemStreamException {
delegate.update(executionContext);
}
#Override
public void close() throws ItemStreamException {
delegate.close();
}
#Override
public void setResource(Resource resource) {
fileName = resource.getFilename();
this.delegate.setResource(resource);
}
String getNextLine() throws UnexpectedInputException, ParseException, NonTransientResourceException, Exception {
return delegate.read();
}
#Override
public SimpleFileBean read() throws Exception, UnexpectedInputException, ParseException, NonTransientResourceException {
SimpleFileBean simpleFileBean = null;
String currentLine = null;
currentLine=delegate.read();
if(currentLine != null) {
simpleFileBean = new SimpleFileBean();
simpleFileBean.getLines().add(currentLine);
while ((currentLine = getNextLine()) != null) {
simpleFileBean.getLines().add(currentLine);
}
return simpleFileBean;
}
return null;
}
}