Creating a file download link using Spring Boot and Thymeleaf

Question

This might sound like a trivial question, but after hours of searching I am yet to find an answer to this. The problem, as far as I understand, is that I am trying to return a FileSystemResource from the controller and Thymeleaf expects me to supply a String resource using which it will render the next page. But since I am returning a FileSystemResource, I get the following error:

org.thymeleaf.exceptions.TemplateInputException: Error resolving template "products/download", template might not exist or might not be accessible by any of the configured Template Resolvers

The controller mapping I have used is:

@RequestMapping(value="/products/download", method=RequestMethod.GET)
public FileSystemResource downloadFile(@Param(value="id") Long id) {
    Product product = productRepo.findOne(id);
    return new FileSystemResource(new File(product.getFileUrl()));
}

My HTML link looks something like this:

<a th:href="${'products/download?id=' + product.id}"><span th:text="${product.name}"></span></a>

I don't want to be redirected anywhere, I just need the file downloaded once the link is clicked. Is this actually the right implementation? I'm not sure.

Answer 1

You need to change the th:href to look like:

<a th:href="@{|/products/download?id=${product.id}|}"><span th:text="${product.name}"></span></a>

Then also you need to change your controller and include the @ResponseBody annotation:

@RequestMapping(value="/products/download", method=RequestMethod.GET)
@ResponseBody
public FileSystemResource downloadFile(@Param(value="id") Long id) {
    Product product = productRepo.findOne(id);
    return new FileSystemResource(new File(product.getFileUrl()));
}

Answer 2

Have a href url like

<a th:href="@{|/download?id=${obj.id}|}">download</a>

Then In controller define like below to write the file to the response object.

@RequestMapping(value="/download", method=RequestMethod.GET)
public void downloadFile(@Param(value="id") Long id,HttpServletResponse response) {
        try {
            Ticket ticket = this.findById(id);
        String fileName =  Paths.get(property.getFileLocation()).resolve(ticket.getFilePath()).toString();
        response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
        String headerKey = "Content-Disposition";
        String headerValue = String.format("attachment; filename=\"%s\"", fileName);
        response.setHeader(headerKey, headerValue);
        FileInputStream inputStream;
        try {
            inputStream = new FileInputStream(fileName);
            try {
                int c;
                while ((c = inputStream.read()) != -1) {
                response.getWriter().write(c);
                }
            } finally {
                if (inputStream != null)
                    try {
                        inputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    response.getWriter().close();
            }
        } catch (IOException e) {
            e.printStackTrace();

        }
    }