Downloading a file from spring controllers
JavaSpringFileDownloadControllerJava Problem Overview
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?
Java Solutions
Solution 1 - Java
@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");
Solution 2 - Java
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));
}
Solution 3 - Java
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.
Solution 4 - Java
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
,PathResource
(since Spring 4.0) orFileSystemResource
,
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);
}
Solution 5 - Java
If you:
- Don't want to load the whole file into a
byte[]
before sending to the response; - Want/need to send/download it via
InputStream
; - Want to have full control of the Mime Type and file name sent;
- Have other
@ControllerAdvice
picking up exceptions for you (or not).
The code below is what you need:
@RequestMapping(value = "/stuff/{stuffId}", method = RequestMethod.GET)
public ResponseEntity<FileSystemResource> downloadStuff(@PathVariable int stuffId)
throws IOException {
String fullPath = stuffService.figureOutFileNameFor(stuffId);
File file = new File(fullPath);
long fileLength = file.length(); // this is ok, but see note below
HttpHeaders respHeaders = new HttpHeaders();
respHeaders.setContentType("application/pdf");
respHeaders.setContentLength(fileLength);
respHeaders.setContentDispositionFormData("attachment", "fileNameIwant.pdf");
return new ResponseEntity<FileSystemResource>(
new FileSystemResource(file), respHeaders, HttpStatus.OK
);
}
More on setContentLength()
: First of all, the content-length
header is optional per the HTTP 1.1 RFC. Still, if you can provide a value, it is better. To obtain such value, know that File#length()
should be good enough in the general case, so it is a safe default choice.
In very specific scenarios, though, it can be slow, in which case you should have it stored previously (e.g. in the DB), not calculated on the fly. Slow scenarios include: if the file is very large, specially if it is on a remote system or something more elaborated like that - a database, maybe.
InputStreamResource
If your resource is not a file, e.g. you pick the data up from the DB, you should use InputStreamResource
. Example:
InputStreamResource isr = new InputStreamResource(...);
return new ResponseEntity<InputStreamResource>(isr, respHeaders, HttpStatus.OK);
Solution 6 - Java
Do not do anything by hand, delegate the work to the framework instead:
- Return
ResponseEntity<Resource>
from a handler method - Specify
Content-Type
explicitly - Set
Content-Disposition
if necessary:- filename
- type
inline
to force preview in a browserattachment
to force a download
@Controller
public class DownloadController {
@GetMapping("/downloadPdf.pdf")
// 1.
public ResponseEntity<Resource> downloadPdf() {
FileSystemResource resource = new FileSystemResource("/home/caco3/Downloads/JMC_Tutorial.pdf");
// 2.
MediaType mediaType = MediaTypeFactory
.getMediaType(resource)
.orElse(MediaType.APPLICATION_OCTET_STREAM);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(mediaType);
// 3
ContentDisposition disposition = ContentDisposition
// 3.2
.inline() // or .attachment()
// 3.1
.filename(resource.getFilename())
.build();
headers.setContentDisposition(disposition);
return new ResponseEntity<>(resource, headers, HttpStatus.OK);
}
}
Explanation
Return ResponseEntity<Resource>
When you return a ResponseEntity<Resource>
, the ResourceHttpMessageConverter
kicks in and writes an appropriate response.
The resource
could be:
If you need to download a file from application resources directory, check out my answer: it explains how to locate the resource in class path using ClassPathResource
Be aware of possibly wrong Content-Type
header set (see FileSystemResource is returned with content type json). That's why this answer suggests setting the Content-Type
explicitly.
Specify Content-Type
explicitly:
Some options are:
- hardcode the header
- use the
MediaTypeFactory
from Spring. - or rely on third party library like Apache Tika
The MediaTypeFactory
allows to discover the MediaType
appropriate for the Resource
(see also /org/springframework/http/mime.types
file)
Set Content-Disposition
if necessary:
Sometimes it is necessary to force a download in a browser or to make the browser open a file as a preview. You can use the Content-Disposition
header to satisfy this requirement:
> The first parameter in the HTTP context is either inline
(default value, indicating it can be displayed inside the Web page, or as the Web page) or attachment
(indicating it should be downloaded; most browsers presenting a 'Save as' dialog, prefilled with the value of the filename parameters if present).
In the Spring Framework a ContentDisposition
can be used.
To preview a file in a browser:
ContentDisposition disposition = ContentDisposition
.builder("inline") // Or .inline() if you're on Spring MVC 5.3+
.filename(resource.getFilename())
.build();
To force a download:
ContentDisposition disposition = ContentDisposition
.builder("attachment") // Or .attachment() if you're on Spring MVC 5.3+
.filename(resource.getFilename())
.build();
Use InputStreamResource
carefully:
Since an InputStream
can be read only once, Spring won't write Content-Length
header if you return an InputStreamResource
(here is a snippet of code from ResourceHttpMessageConverter
):
@Override
protected Long getContentLength(Resource resource, @Nullable MediaType contentType) throws IOException {
// Don't try to determine contentLength on InputStreamResource - cannot be read afterwards...
// Note: custom InputStreamResource subclasses could provide a pre-calculated content length!
if (InputStreamResource.class == resource.getClass()) {
return null;
}
long contentLength = resource.contentLength();
return (contentLength < 0 ? null : contentLength);
}
In other cases it works fine:
~ $ curl -I localhost:8080/downloadPdf.pdf | grep "Content-Length"
Content-Length: 7554270
Solution 7 - Java
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();
}
}
Solution 8 - Java
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);
}
Solution 9 - Java
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";
Solution 10 - Java
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());
}
}
Solution 11 - Java
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
Solution 12 - Java
If it helps anyone. You can do what the accepted answer by Infeligo has suggested but just put this extra bit in the code for a forced download.
response.setContentType("application/force-download");
Solution 13 - Java
In my case I'm generating some file on demand, so also url has to be generated.
For me works something like that:
@RequestMapping(value = "/files/{filename:.+}", method = RequestMethod.GET, produces = "text/csv")
@ResponseBody
public FileSystemResource getFile(@PathVariable String filename) {
String path = dataProvider.getFullPath(filename);
return new FileSystemResource(new File(path));
}
Very important is mime type in produces
and also that, that name of the file is a part of the link so you has to use @PathVariable
.
HTML code looks like that:
<a th:href="@{|/dbreport/files/${file_name}|}">Download</a>
Where ${file_name}
is generated by Thymeleaf in controller and is i.e.: result_20200225.csv, so that whole url behing link is: example.com/aplication/dbreport/files/result_20200225.csv
.
After clicking on link browser asks me what to do with file - save or open.
Solution 14 - Java
This can be a useful answer.
https://stackoverflow.com/questions/60034234/is-it-ok-to-export-data-as-pdf-format-in-frontend/
Extending to this, adding content-disposition as an attachment(default) will download the file. If you want to view it, you need to set it to inline.
Solution 15 - Java
I had to add this to download any file
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition",
"attachment;filename="+"file.txt");
all code:
@Controller
public class FileController {
@RequestMapping(value = "/file", method =RequestMethod.GET)
@ResponseBody
public FileSystemResource getFile(HttpServletResponse response) {
final File file = new File("file.txt");
response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition",
"attachment;filename="+"file.txt");
return new FileSystemResource(file);
}
}