How to convert S3Object to File and return the File Object in Java using try with resources?

Mohammed Idris :

I have a service method which returns a File Object from AWS S3 bucket given a fileName. I would like to convert the S3Object to a File object and return the same.

I do not want to use any temp location to download the file, just want to convert the S3Object to File Object and return it.

I would also like to use try with resources and IOUtils for the same.

My question is what is the right way to perform com.amazonaws.util.IOUtils.copy(InputStream in, OutputStream out) method to get the File Object. This File object will be used by the calling method for further processing hence I do not want to save it locally. I tried something like this but it throws FileNotFoundException.

I am sure I am missing something in this, may be IOUtils.copy has to be used differently. or I am not using try with resources correctly.

    public File getFileFromBucket(String fileName) {
        GetObjectRequest getObjectRequest = new GetObjectRequest(aWSBucketName, fileName);
        S3Object s3Object = aWSS3client.getObject(getObjectRequest);
        File s3File = new File(fileName);
        try (FileOutputStream fos = new FileOutputStream(s3File)) { //throws Exception
            IOUtils.copy(s3Object.getObjectContent(), fos); 
        } catch (IOException e) {
            log.debug("IOException Occurred while fetching file {}", fileName);
            e.printStacktrace();
        }
        return s3File;
    }

What is the right way to return the File? Any help is appreciated, thanks in advance.

Edit

If I do not want to save a File Object locally, is it advisable to return the InputStream to the calling method?

As mentioned, the calling method uses apache poi library to parse the excel file.

org.apache.poi.xssf.usermodel.XSSFWorkbook.XSSFWorkbook(InputStream is) this method anyway takes InputStream as a param.

I do not know why I wanted to convert it to a File to begin with.

Question:

Is it advisable to send the S3Object.getObjectContent() as an InputStream to the calling method or is there a better way to do it?

Mohammed Idris :

After consulting my seniors I found that it is fine to send the InputStream to the calling method.

If the InputStream needs to be save to a local system, then IOUtils.copy can be used whenever necessary.

Conversion of InputStream to File and then back to InputStream is a waste of computation.

Hence my method is simply returning the ObjectContent like this:

public InputStream getFileInputStreamFromBucket(String fileName) {
        GetObjectRequest getObjectRequest = new GetObjectRequest(aWSBucketName, fileName);
        S3Object s3Object = aWSS3client.getObject(getObjectRequest);
        InputStream fileInputStream = s3Object.getObjectContent();
        log.debug("File Input Stream fetched from s3 bucket for File {} ", fileName);
        return fileInputStream;
    }

This seems to be the right choice.

If anyone has a better way to send back the InputStream please feel free to Post an answer.