java - Spring MVC : large files for download, OutOfMemoryException

Question

How to provide large files for download through spring controller ? I followed few discussions on similar topic :

Downloading a file from spring controllers

but those solutions fails for large files ~ 300mb - 600mb. I am getting OutOfMemoryException on the last line :

@RequestMapping(value = "/file/{dummyparam}.pdf", method = RequestMethod.GET, produces=MediaType.APPLICATION_OCTET_STREAM_VALUE)
public @ResponseBody byte[] getFile(@PathVariable("dummyparam") String dummyparam, HttpServletResponse response) {
.
.       
InputStream is = new FileInputStream(resultFile);

response.setHeader("Content-Disposition", "attachment; filename="dummyname " + dummyparam + ".pdf"");
.
.         
return IOUtils.toByteArray(is);

My (naive) assumption was that IOUtils will handle even large files but this is not obviously happening. Is there any way how to split file into chunks as download is in progress ? Files are usually around 300 - 600mb large. Max number of concurrent downloads is estimated to 10.

Easy way would be to link files as static content in the webserver directory but we would like to try do it in within our Spring app.

Answer 1

It is because you are reading the entire file into memory, use a buffered read and write instead.

@RequestMapping(value = "/file/{dummyparam}.pdf", method = RequestMethod.GET, produces=MediaType.APPLICATION_OCTET_STREAM_VALUE)
public void getFile(@PathVariable("dummyparam") String dummyparam, HttpServletResponse response) {


    InputStream is = new FileInputStream(resultFile);

    response.setHeader("Content-Disposition", "attachment; filename="dummyname " + dummyparam + ".pdf"");


    int read=0;
    byte[] bytes = new byte[BYTES_DOWNLOAD];
    OutputStream os = response.getOutputStream();

    while((read = is.read(bytes))!= -1){
        os.write(bytes, 0, read);
    }
    os.flush();
    os.close(); 
}