File download is very common to any type of web application. Let’s see how this done in spring framework and java. This is pretty easy and you can add/remove code segments as you want. The given code segments are written as I thought and comments will give you an idea about each code.
Let’s go then, Please follow below simple steps to create your own file down-loader;
Step 1:
Create the spring controller.
@RequestMapping(value = "/downloadFile", method = RequestMethod.GET)
public void getUserProfilePage(@RequestParam("fileName") String fileName,
HttpServletRequest request, HttpServletResponse response) {
FileDownloadManager downloadManager = new FileDownloadManager();
try {
downloadManager.downloadFile(fileName, response);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Step 2:
Create a java Class “DownloadManager” and create below method.
public void downloadFile(String fileName, HttpServletResponse response) throws IOException {
// reads input file from an absolute path
try {
//get fixed file path from the property file of the project
String filePath = CommonUtil.getValueFromFile("application", "file.upload.location") + fileName;
File downloadFile = new File(filePath);
FileInputStream inStream = new FileInputStream(downloadFile);
// gets MIME type of the file
String mimeType = new MimetypesFileTypeMap().getContentType(downloadFile);
if (mimeType == null) {
// set to binary type if MIME mapping not found
mimeType = "application/octet-stream";
} else if (StringUtils.equals(FilenameUtils.getExtension(filePath), "pdf")
|| StringUtils.equals(FilenameUtils.getExtension(filePath), "PDF")) {
mimeType = "application/pdf";
}
System.out.println("MIME type: " + mimeType);
// modifies response
response.setContentType(mimeType);
response.setHeader("Content-Disposition", "inline; filename=" + downloadFile.getName());
response.setContentLength((int) downloadFile.length());
// if you want to forces download you can use below
// String headerKey = "Content-Disposition";
// String headerValue = String.format("attachment; filename=\"%s\"", downloadFile.getName());
// response.setHeader(headerKey, headerValue);
// obtains response's output stream
OutputStream outStream = response.getOutputStream();
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = inStream.read(buffer)) != -1) {
outStream.write(buffer, 0, bytesRead);
}
inStream.close();
outStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
For mime type; you can use different java libraries like MimeMagic, Tika or use URLConnection. But I have used simple MimetypesFileTypeMap which is available form java 1.7 as I know.
Now you can enjoy the file down-loader by accessing the spring controller via browser. Please contact me for further information.
Java Source Point 