Downloading a file using Vaadin

Question

Here is my code to try to download a file using Vaadin. The button function is added within a component.

Button button = new Button("Generate");
@Override
public void buttonClick(ClickEvent event) {
try{
    VaadinResponse resp = VaadinService.getCurrentResponse();
    HttpServletResponse response = (HttpServletResponse) resp;
    response.setContentType("text/csv");
    response.setHeader("Content-Disposition", "attachment; filename=\"Report.csv\"");
    OutputStream outputStream = response.getOutputStream();
    String outputResult = "Id,name,dept,salary\n";
    outputStream.write(outputResult.getBytes());
    outputStream.flush();
    outputStream.close();
}catch(Exception e){
    e.printStackTrace();
}

But I get the following error Invalid JSON response from server:Id,name,dept,salary

Please help in identifying where I have gone wrong.

Thanks

Answer 1

You can't implement a file download like that. The Vaadin client is expecting a specifically formatted response. You can use a FileDownloader extension instead: https://vaadin.com/docs/v8/framework/articles/LettingTheUserDownloadAFile