Using Servlet to Export File

 

String helloworld = "hello world";
 response.setContentType("application/x-download");
 // must be set the Header before any data has wrote into it.
 response.addHeader("Content-Disposition","attachment;filename=helloworld.txt");
 

 byte[] ins = helloworld.getBytes();
 response.getOutputStream().write(ins);

 

The things that u should only concerned is that, if u want to set Header or ContentType that basic impacts on the format of the Response, u should set them before u added any data in the response.getOutputStream().