Excel manipulation and testing in Java


In my current project I am doing a lot of Excel manipulation using Apache POI and Jacob COM libraries. One of the first challenges I faced was to write test cases that could read these Excel files and process them. This wasn't rocket science, but I want to blog about this so that a. I can share my approach and b. So that I can use this blog post in case I want to do this in the future.

So my Excel file which I want to test is stored in /src/test/resources as Gantt_XLS.xls in a Maven setup.So here is my test case -

public void shouldConvertExcelFile() throws IOException {
    InputStream inputStream = getClass().getResourceAsStream("/Gantt_XLS.xls");
    File file = convertToFile(inputStream);
    String outpath = FileUtils.getTempDirectory().getCanonicalPath() + File.separator + UUID.randomUUID().toString();
    FileUtils.forceMkdir(new File(outpath));
    excelConverter.doExcelConversion(file, outpath);

private File convertToFile(InputStream inputStream) throws IOException {
    String path = FileUtils.getTempDirectoryPath() + File.separator + UUID.randomUUID().toString() + File.separator;
    FileUtils.forceMkdir(new File(path));
    File f = new File(path + "Gantt_XLS.xls");
    OutputStream out = new FileOutputStream(f);
    byte buf[] = new byte[1024];
    int len;
    while ((len = inputStream.read(buf)) > 0) {
        out.write(buf, 0, len);
    return f;

So in this code, I am reading a file in the test resources folder as a InputStream, writing the stream to a file in a unique directory in my OS's temp directory and finally processing the file.

Now, the other task I am trying to do is converting a SpreadsheetML file to a binary Excel file. SpreadsheetML is MS Office Excel 2003 format for storing Excel files in XML format. For this I am using the Jacob COM library.

    public boolean doConversionTask() {
        boolean success = true;
        try {
            ActiveXComponent excel = new ActiveXComponent("Excel.Application");
            Dispatch workbook = Dispatch.call(excel.getProperty("Workbooks").toDispatch(), "Open", inFilePath).toDispatch();
            Dispatch.call(workbook, "SaveAs", tempFilePath, 43);
            Dispatch.call(excel.getProperty("Workbooks").toDispatch(), "Close");
        } catch (Exception e) {
            log.error("Error in converting HTML to Excel : " + e.getMessage());
            success =  false;
        } finally {
             excel.invoke("Quit", new Variant[]{});
        return success;

Hopefully this will help someone out there.