Beanio - How to write to stream object

Question

I am trying to create a fixed length file output using beanio. I don't want to write the physical file, instead I want to write content to an OutputStream.

ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
StreamFactory factory = StreamFactory.newInstance(); 
StreamBuilder builder = new StreamBuilder("sb")
            .format("fixedlength")
            .parser(new FixedLengthParserBuilder())
            .addRecord(Team.class);

factory.define(builder);
OutputStreamWriter writer = new OutputStreamWriter(outputStream, StandardCharsets.UTF_8);
BeanWriter bw = sf.createWriter("sb", writer);

bw.write(teamVO) // teamVO has some value.

try(OutputStream os = new FileOutputStream("file.txt")){
    outputStream.writeTo(os); //Doing this only to check outputStream has some value
}

Here the file created, file.txt has no content in it, It is of size 0 kb.

I am able to write the file in the following method, but as I don't want to write the file in physical location, I thought of writing the contents in to a outputStream and then later in a different method, it can be converted in to a file

//This is working and creates file successfully
StreamFactory factory = StreamFactory.newInstance();
StreamBuilder builder = new StreamBuilder("sb")
                .format("fixedlength")
                .parser(new FixedLengthParserBuilder())
                .addRecord(Team.class)
        
factory.define(builder);
BeanWriter bw = factory.createWriter("sb", new File("file.txt"));
bw.write(teamVO);

Why in the first approach the file is created with size 0 kb?

Answer 1

It looks like you haven't written enough data to the OutputstreamWriter for it to push some data to the underlying ByteArrayOutputStream. You have 2 options here.

1. Flush the writer object manually and then close it. This will then write the data to the outputStream. I would not recommend this approach because the writer may not be flushed or closed should there be any Exception before you could manually flush and close the writer.
2. Use a try-with-resource block for the writer which should take care of closing the writer and ultimately flushing the data to the outputStream

This should do the trick:

final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
try (final OutputStreamWriter writer = new OutputStreamWriter(outputStream) ) {
  final BeanWriter bw = factory.createWriter("sb", writer);

  final Team teamVO = new Team();
  teamVO.setName("TESTING");

  bw.write(teamVO); // teamVO has some value.
}

try (OutputStream os = new FileOutputStream("file.txt") ) {
  outputStream.writeTo(os); // Doing this only to check outputStream has some value
}