I want to download files using SpringBoot - spring-boot

Question

An attempt was made to implement file downloads through the SpringBoot MVC structure. There is no error, it says it has run normally, but the download does not proceed.
All information about the file is entered correctly, and also the path and name of the file are entered correctly.
I'd like to know why the download doesn't proceed even though there's no error.
#RestController
public class Controller {
#PostMapping("/fileDownload")
public void fileDownload(#RequestBody BoardFileDTO dto,HttpServletRequest request,HttpServletResponse response) throws UnsupportedEncodingException {
//File contains all stored paths, names, and extensions
Path fileNamePath = Paths.get(Directory + dto.getFile_save_name()).toAbsolutePath();
String filename = dto.getFile_save_name(); //The name of the saved file
String downname = dto.getFile_name(); //The name of the file to be saved
if (filename == null || "".equals(filename)) {
filename = downname;
}
try {
String browser = request.getHeader("User-Agent");
//File Encoding
if (browser.contains("MSIE") || browser.contains("Trident")
|| browser.contains("Chrome")) {
filename = URLEncoder.encode(filename, "UTF-8").replaceAll("\\+",
"%20");
} else {
filename = new String(filename.getBytes("UTF-8"), "ISO-8859-1");
}
} catch (UnsupportedEncodingException ex) {
System.out.println("UnsupportedEncodingException");
}
System.out.println(fileNamePath);
File file1 = new File(fileNamePath.toString());
if (!file1.exists()) {
return ;
}
// Specifying a File
response.setContentType("application/octer-stream");
response.setHeader("Content-Transfer-Encoding", "binary;");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
try {
OutputStream os = response.getOutputStream();
FileInputStream fis = new FileInputStream(fileNamePath.toString());
int ncount = 0;
byte[] bytes = new byte[512];
while ((ncount = fis.read(bytes)) != -1 ) {
os.write(bytes, 0, ncount);
}
fis.close();
os.close();
} catch (FileNotFoundException ex) {
System.out.println("FileNotFoundException");
} catch (IOException ex) {
System.out.println("IOException");
}
}
}

Answer 1

Your code is a bit convoluted imho. A couple of issues I see with your code
Using Path.toString to convert to a File, use the proper factory methods instead or use java.nio.Files to check the existence.
Your content-type is wrong application/octer-stream isn't a known content-type (you probably want application/octet-stream.
Copying from a Path or File is better done with either the StreamUtils from Spring or the java.nio.Files class (if you already have a Path use that).
#PostMapping("/fileDownload")
public void fileDownload(#RequestBody BoardFileDTO dto, HttpServletRequest request, HttpServletResponse response) throws UnsupportedEncodingException {
//File contains all stored paths, names, and extensions
Path fileNamePath = Paths.get(Directory, dto.getFile_save_name()).toAbsolutePath();
if (!Files.exists(fileNamePath)) {
return;
}
String filename = determineFilename(dto, request);
// Specifying a File
response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
response.setHeader("Content-Transfer-Encoding", "binary;");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
try {
Files.copy(fileNamePath, response.getOutputStream());
} catch (IOException ex) {
System.out.println("IOException");
}
}
private static String determineFilename(BoardFileDTO dto, HttpServletRequest request) {
String filename = dto.getFile_save_name(); //The name of the saved file
if (filename == null || "".equals(filename)) {
filename = dto.getFile_name();
}
String browser = request.getHeader("User-Agent");
//File Encoding
if (browser.contains("MSIE") || browser.contains("Trident") || browser.contains("Chrome")) {
filename = URLEncoder.encode(filename, StandardCharsets.UTF_8).replaceAll("\\+", "%20");
} else {
filename = new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);
}
return filename;
}
It would write it something like that. As you have a path use the java.nio.Files to check for existence and copying. Use constants for mediatypes and charsets.
Your error handling is quite basic (I would say non-existing and at least not proper) as the processing just stops and returns an empty 200 to the client. No information what so ever.
I took the liberty to factor out the logic to determine the filename, which should make your code more readable.