Download A File On click of a link using spring mvc - spring

Question

When I click on any link the content should be downloaded
But this is what I get.
MastercourseController.java
#RequestMapping(value = { ControllerUriConstant.download_file }, method = RequestMethod.GET)
#ResponseBody
public void downloadingAFileById(#RequestParam("id") String id, Model model, HttpServletRequest request)
throws TechnoShineException, IOException {
String filePath = "D:/dev/testFIle.txt";
long download = Long.parseLong(id);
byte[] b = masterCourseFileFormService.getAllDownloadable(download);
OutputStream outputStream = new FileOutputStream(filePath);
outputStream.write(b);
outputStream.close();
}
MasterCourseService
public byte[] getAllDownloadable(long id) throws TechnoShineException
{
return masterCourseFormUploadDao.getAllDownloadableFiles(id);
}
MasterCourseDao
public byte[] getAllDownloadableFiles(long id) throws TechnoShineException
{
return masterCourseFormUploadMapper.getAllDownloadable(id);
}
MasterCourseMapper
public byte[] getAllDownloadable(long id) throws TechnoShineException;

Answer 1

You are writing the data returned by getAllDownloadable(..) to a hard-coded file. Are you sure that is what you want? I think you want to write the content returned by getAllDownloadable(..) to be written into the response. That can be done by adding a method parameter of the type HttpServletResponse to your mapping and writing into the output stream returned by HttpServletResponse#getOutputStream() and flushing (not closing!) that stream at the end.
Furthermore you have to remove the #ResponseBody annotation as this is meant to be used if the value that is returned by the mapping method returns the data that should directly be sent to the client (i.e. when sending a JSON data object or a string) without passing it to the template engine. As you are not returning anything you can remove this annotation.
Furthermore you have to set the content type of your response by invoking HttpServletResponse#setContentType(contentType: String).
In your case, the invocation would be the following:
response.setContentType("text/plain");
You complete method would look like this:
#RequestMapping(
value = ControllerUriConstant.download_file,
method = RequestMethod.GET
)
public void downloadingAFileById(#RequestParam("id") String id, HttpServletResponse response)
throws TechnoShineException, IOException {
long download = Long.parseLong(id);
byte[] b = masterCourseFileFormService.getAllDownloadable(download);
response.getOutputStream().write(b);
response.getOutputStream().flush();
}