InputStream xls file can't be decoded-CodePudding

I use an endpoint in order to upload a .xlsx or .xls file. After that I am storing the encoded excel file (base64) to a String. In order to parse and handle the values of excel I need to decode that file.

Upload service class:

public BulkUploadResponse validateFile(BulkUploadRequest request) {
        final String pfx = String.format("validateFile: ");

        BulkUploadResponse response = new BulkUploadResponse();

        String delimiters = "\\s |,";
        
        String[] tokensVal = request.getContent().split(delimiters);
        String fileContentEncoded = tokensVal[tokensVal.length-1];

        InputStream fileContent = new ByteArrayInputStream(new String(Base64.getDecoder().decode(fileContentEncoded), UTF_8).getBytes(UTF_8));

Then I call a class where I convert the data included in excel file parsing as a parameter the fileContent which is supposed to be decoded.

BulkVignetteCustomer customerVignettes = bulkVignetteCustomerConverter.convert(fileContent);

Finally I use the Workbook package in order to parse that file

Example:

@Override
    public BulkVignetteCustomer convert(InputStream fileContent) {

        try {
            Workbook wb = WorkbookFactory.create(fileContent);
            FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
            Sheet sheet = wb.getSheetAt(0);
            Iterator rows = sheet.iterator();
            (...)

Error that I get:

java.lang.IllegalArgumentException: Your InputStream was neither an OLE2 stream, nor an OOXML stream at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:89)

Any thoughts on how to decode the file without any errors?

Thank you!

CodePudding user response：

This line seems very strange to me:

InputStream fileContent = new ByteArrayInputStream(new String(Base64.getDecoder().decode(fileContentEncoded), UTF_8).getBytes(UTF_8));

You have an Excel file which isn't plain text but a big binary blob at this stage. Why do you use a String here?

So the binary blob is encoded as Base64. You can directly get the bytes out of the decoder and put them into the ByteArrayInputStream:

InputStream fileContent = new ByteArrayInputStream(Base64.getDecoder().decode(fileContentEncoded));

To verify this part of your application you can store the bytes to a file and try to open it with Excel.