how to prepare pdf report using thymleaf and Flying Saucer in spring boot

I am using Flying Saucer for pdf report creation and template using thymleaf but the problem is when I am converting the template I am getting this error.

org.thymeleaf.exceptions.TemplateProcessingException: Link base "/download-pdf/{refno}" cannot be context relative (/...) unless the context used for executing the engine implements the org.thymeleaf.context.IWebContext interface

In thymleaf template I am using this code: Download PDF Document

I have taken the reference of https://github.com/tuhrig/Flying_Saucer_PDF_Generation.

Before that, I have used Itext for Pdf report but using Itext PDF is converting but CSS is not supporting properly in the case of Itext.

This is the code for Flying Saucer I am using in Java.

@RequestMapping("download-pdf/{refno}")
    public void generatePdf(@PathVariable("refno") Long refno) throws Exception {
        ClassLoaderTemplateResolver templateResolver = new ClassLoaderTemplateResolver();
        templateResolver.setPrefix("templates/");
        templateResolver.setSuffix(".html");
        templateResolver.setTemplateMode(TemplateMode.HTML);
        templateResolver.setCharacterEncoding(UTF_8);

    TemplateEngine templateEngine = new TemplateEngine();
    templateEngine.setTemplateResolver(templateResolver);
    System.out.println(refno + " " + "downlodadaf");
    complaintDto = complaintRepo.findById(refno).orElse(null);
    System.out.println(complaintDto.getcMobile() + " dfdf      " + complaintDto.getRefno());

    Context context = new Context();
    context.setVariable("complaintPdfBean", complaintDto);
    String renderedHtmlContent = templateEngine.process("complant-privew", context);
    String xHtml = convertToXhtml(renderedHtmlContent);

    ITextRenderer renderer = new ITextRenderer();
    renderer.getFontResolver().addFont("Code39.ttf", IDENTITY_H, EMBEDDED);
    String baseUrl = FileSystems.getDefault().getPath("src", "main", "resources").toUri().toURL().toString();
    renderer.setDocumentFromString(xHtml, baseUrl);
    renderer.layout();

    // And finally, we create the PDF:
    OutputStream outputStream = new FileOutputStream("inline; filename=complantprivew.pdf");
    renderer.createPDF(outputStream);
    outputStream.close();
}

private String convertToXhtml(String html) throws UnsupportedEncodingException {
    Tidy tidy = new Tidy();
    tidy.setInputEncoding(UTF_8);
    tidy.setOutputEncoding(UTF_8);
    tidy.setXHTML(true);
    ByteArrayInputStream inputStream = new ByteArrayInputStream(html.getBytes(UTF_8));
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    tidy.parseDOM(inputStream, outputStream);
    return outputStream.toString(UTF_8);
}