Downloading a file from spring controllers

I have a requirement where I need to download a PDF from the website. The PDF needs to be generated within the code, which I thought would be a combination of freemarker and a PDF generation framework like iText. Any better way?

However, my main problem is how do I allow the user to download a file through a Spring Controller?

What I can quickly think of is, generate the pdf and store it in webapp/downloads/< RANDOM-FILENAME>.pdf from the code and send a forward to this file using HttpServletRequest

request.getRequestDispatcher("/downloads/<RANDOM-FILENAME>.pdf").forward(request, response);

or if you can configure your view resolver something like,

<bean id="pdfViewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="order" value=”2″/>
<property name="prefix" value="/downloads/" />
<property name="suffix" value=".pdf" />
</bean>

then just return

return "RANDOM-FILENAME";

I was able to stream line this by using the built in support in Spring with it's ResourceHttpMessageConverter. This will set the content-length and content-type if it can determine the mime-type


@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
@ResponseBody
public FileSystemResource getFile(@PathVariable("file_name") String fileName) {
return new FileSystemResource(myService.getFileFor(fileName));
}

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
@PathVariable("file_name") String fileName,
HttpServletResponse response) {
try {
// get your file as InputStream
InputStream is = ...;
// copy it to response's OutputStream
org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());
response.flushBuffer();
} catch (IOException ex) {
log.info("Error writing file to output stream. Filename was '{}'", fileName, ex);
throw new RuntimeException("IOError writing file to output stream");
}

}

Generally speaking, when you have `response.getOutputStream()`, you can write anything there. You can pass this output stream as a place to put generated PDF to your generator. Also, if you know what file type you are sending, you can set

response.setContentType("application/pdf");

This code is working fine to download a file automatically from spring controller on clicking a link on jsp.



@RequestMapping(value="/downloadLogFile")
public void getLogFile(HttpSession session,HttpServletResponse response) throws Exception {
try {
String filePathToBeServed = //complete file name with path;
File fileToDownload = new File(filePathToBeServed);
InputStream inputStream = new FileInputStream(fileToDownload);
response.setContentType("application/force-download");
response.setHeader("Content-Disposition", "attachment; filename="+fileName+".txt");
IOUtils.copy(inputStream, response.getOutputStream());
response.flushBuffer();
inputStream.close();
} catch (Exception e){
LOGGER.debug("Request could not be completed at this moment. Please try again.");
e.printStackTrace();
}

}

Below code worked for me to generate and download a text file.

@RequestMapping(value = "/download", method = RequestMethod.GET)
public ResponseEntity<byte[]> getDownloadData() throws Exception {

String regData = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.";
byte[] output = regData.getBytes();

HttpHeaders responseHeaders = new HttpHeaders();
responseHeaders.set("charset", "utf-8");
responseHeaders.setContentType(MediaType.valueOf("text/html"));
responseHeaders.setContentLength(output.length);
responseHeaders.set("Content-disposition", "attachment; filename=filename.txt");

return new ResponseEntity<byte[]>(output, responseHeaders, HttpStatus.OK);
}

something like below

@RequestMapping(value = "/download", method = RequestMethod.GET)
public void getFile(HttpServletResponse response) {
try {
DefaultResourceLoader loader = new DefaultResourceLoader();
InputStream is = loader.getResource("classpath:META-INF/resources/Accepted.pdf").getInputStream();
IOUtils.copy(is, response.getOutputStream());
response.setHeader("Content-Disposition", "attachment; filename=Accepted.pdf");
response.flushBuffer();
} catch (IOException ex) {
throw new RuntimeException("IOError writing file to output stream");
}
}

You can display PDF or download it examples [here][1]


[1]:

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With Spring 3.0 you can use the `HttpEntity` return object. If you use this, then your controller does not need a `HttpServletResponse` object, and therefore it is easier to test.
*Except this, this answer is relative equals to the one of Infeligo*.

If the return value of your pdf framework is an byte array *(read the second part of my answer for other return values)* :


@RequestMapping(value = "/files/{fileName}", method = RequestMethod.GET)
public HttpEntity<byte[]> createPdf(
@PathVariable("fileName") String fileName) throws IOException {

byte[] documentBody = this.pdfFramework.createPdf(filename);

HttpHeaders header = new HttpHeaders();
header.setContentType(MediaType.APPLICATION_PDF);
header.set(HttpHeaders.CONTENT_DISPOSITION,
"attachment; filename=" + fileName.replace(" ", "_"));
header.setContentLength(documentBody.length);

return new HttpEntity<byte[]>(documentBody, header);
}


----
**If the return type of your PDF Framework (`documentBbody`) is not already a byte array** (and also no `ByteArrayInputStream`) then it would been wise **NOT** to make it a byte array first. Instead it is better to use:

- [`InputStreamResource`][1],
- [`PathResource`][2] (since Spring 4.0) or
- [`FileSystemResource`][3],

example with `FileSystemResource`:

@RequestMapping(value = "/files/{fileName}", method = RequestMethod.GET)
public HttpEntity<byte[]> createPdf(
@PathVariable("fileName") String fileName) throws IOException {

File document = this.pdfFramework.createPdf(filename);

HttpHeaders header = new HttpHeaders();
header.setContentType(MediaType.APPLICATION_PDF);
header.set(HttpHeaders.CONTENT_DISPOSITION,
"attachment; filename=" + fileName.replace(" ", "_"));
header.setContentLength(document.length());

return new HttpEntity<byte[]>(new FileSystemResource(document),
header);
}

[1]:

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[2]:

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[3]:

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You should be able to write the file on the response directly. Something like


response.setContentType("application/pdf");
response.setHeader("Content-Disposition", "attachment; filename=\"somefile.pdf\"");

and then write the file as a binary stream on `response.getOutputStream()`. Remember to do `response.flush()` at the end and that should do it.

The following solution work for me

@RequestMapping(value="/download")
public void getLogFile(HttpSession session,HttpServletResponse response) throws Exception {
try {

String fileName="archivo demo.pdf";
String filePathToBeServed = "C:\\software\\Tomcat 7.0\\tmpFiles\\";
File fileToDownload = new File(filePathToBeServed+fileName);

InputStream inputStream = new FileInputStream(fileToDownload);
response.setContentType("application/force-download");
response.setHeader("Content-Disposition", "attachment; filename="+fileName);
IOUtils.copy(inputStream, response.getOutputStream());
response.flushBuffer();
inputStream.close();
} catch (Exception exception){
System.out.println(exception.getMessage());
}

}