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save images uploaded by client in this folder in web container using servlet [duplicate]

I read here that one should not save the file in the server anyway as it is not portable, transactional and requires external parameters. However, given that I need a tmp solution for tomcat (7) and that I have (relative) control over the server machine I want to know :
What is the best place to save the file ? Should I save it in /WEB-INF/uploads (advised against here) or someplace under $CATALINA_BASE (see here) or ... ? The JavaEE 6 tutorial gets the path from the user (:wtf:). NB : The file should not be downloadable by any means.
Should I set up a config parameter as detailed here ? I'd appreciate some code (I'd rather give it a relative path - so it is at least Tomcat portable) - Part.write() looks promising - but apparently needs a absolute path
I'd be interested in an exposition of the disadvantages of this approach vs a database/JCR repository one
Unfortunately the FileServlet by #BalusC concentrates on downloading files, while his answer on uploading files skips the part on where to save the file.
A solution easily convertible to use a DB or a JCR implementation (like jackrabbit) would be preferable.

Store it anywhere in an accessible location except of the IDE's project folder aka the server's deploy folder, for reasons mentioned in the answer to Uploaded image only available after refreshing the page:
Changes in the IDE's project folder does not immediately get reflected in the server's work folder. There's kind of a background job in the IDE which takes care that the server's work folder get synced with last updates (this is in IDE terms called "publishing"). This is the main cause of the problem you're seeing.
In real world code there are circumstances where storing uploaded files in the webapp's deploy folder will not work at all. Some servers do (either by default or by configuration) not expand the deployed WAR file into the local disk file system, but instead fully in the memory. You can't create new files in the memory without basically editing the deployed WAR file and redeploying it.
Even when the server expands the deployed WAR file into the local disk file system, all newly created files will get lost on a redeploy or even a simple restart, simply because those new files are not part of the original WAR file.
It really doesn't matter to me or anyone else where exactly on the local disk file system it will be saved, as long as you do not ever use getRealPath() method. Using that method is in any case alarming.
The path to the storage location can in turn be definied in many ways. You have to do it all by yourself. Perhaps this is where your confusion is caused because you somehow expected that the server does that all automagically. Please note that #MultipartConfig(location) does not specify the final upload destination, but the temporary storage location for the case file size exceeds memory storage threshold.
So, the path to the final storage location can be definied in either of the following ways:
Hardcoded:
File uploads = new File("/path/to/uploads");
Environment variable via SET UPLOAD_LOCATION=/path/to/uploads:
File uploads = new File(System.getenv("UPLOAD_LOCATION"));
VM argument during server startup via -Dupload.location="/path/to/uploads":
File uploads = new File(System.getProperty("upload.location"));
*.properties file entry as upload.location=/path/to/uploads:
File uploads = new File(properties.getProperty("upload.location"));
web.xml <context-param> with name upload.location and value /path/to/uploads:
File uploads = new File(getServletContext().getInitParameter("upload.location"));
If any, use the server-provided location, e.g. in JBoss AS/WildFly:
File uploads = new File(System.getProperty("jboss.server.data.dir"), "uploads");
Either way, you can easily reference and save the file as follows:
File file = new File(uploads, "somefilename.ext");
try (InputStream input = part.getInputStream()) {
Files.copy(input, file.toPath());
}
Or, when you want to autogenerate an unique file name to prevent users from overwriting existing files with coincidentally the same name:
File file = File.createTempFile("somefilename-", ".ext", uploads);
try (InputStream input = part.getInputStream()) {
Files.copy(input, file.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
How to obtain part in JSP/Servlet is answered in How to upload files to server using JSP/Servlet? and how to obtain part in JSF is answered in How to upload file using JSF 2.2 <h:inputFile>? Where is the saved File?
Note: do not use Part#write() as it interprets the path relative to the temporary storage location defined in #MultipartConfig(location). Also make absolutely sure that you aren't corrupting binary files such as PDF files or image files by converting bytes to characters during reading/writing by incorrectly using a Reader/Writer instead of InputStream/OutputStream.
See also:
How to save uploaded file in JSF (JSF-targeted, but the principle is pretty much the same)
Simplest way to serve static data from outside the application server in a Java web application (in case you want to serve it back)
How to save generated file temporarily in servlet based web application

I post my final way of doing it based on the accepted answer:
#SuppressWarnings("serial")
#WebServlet("/")
#MultipartConfig
public final class DataCollectionServlet extends Controller {
private static final String UPLOAD_LOCATION_PROPERTY_KEY="upload.location";
private String uploadsDirName;
#Override
public void init() throws ServletException {
super.init();
uploadsDirName = property(UPLOAD_LOCATION_PROPERTY_KEY);
}
#Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// ...
}
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
Collection<Part> parts = req.getParts();
for (Part part : parts) {
File save = new File(uploadsDirName, getFilename(part) + "_"
+ System.currentTimeMillis());
final String absolutePath = save.getAbsolutePath();
log.debug(absolutePath);
part.write(absolutePath);
sc.getRequestDispatcher(DATA_COLLECTION_JSP).forward(req, resp);
}
}
// helpers
private static String getFilename(Part part) {
// courtesy of BalusC : http://stackoverflow.com/a/2424824/281545
for (String cd : part.getHeader("content-disposition").split(";")) {
if (cd.trim().startsWith("filename")) {
String filename = cd.substring(cd.indexOf('=') + 1).trim()
.replace("\"", "");
return filename.substring(filename.lastIndexOf('/') + 1)
.substring(filename.lastIndexOf('\\') + 1); // MSIE fix.
}
}
return null;
}
}
where :
#SuppressWarnings("serial")
class Controller extends HttpServlet {
static final String DATA_COLLECTION_JSP="/WEB-INF/jsp/data_collection.jsp";
static ServletContext sc;
Logger log;
// private
// "/WEB-INF/app.properties" also works...
private static final String PROPERTIES_PATH = "WEB-INF/app.properties";
private Properties properties;
#Override
public void init() throws ServletException {
super.init();
// synchronize !
if (sc == null) sc = getServletContext();
log = LoggerFactory.getLogger(this.getClass());
try {
loadProperties();
} catch (IOException e) {
throw new RuntimeException("Can't load properties file", e);
}
}
private void loadProperties() throws IOException {
try(InputStream is= sc.getResourceAsStream(PROPERTIES_PATH)) {
if (is == null)
throw new RuntimeException("Can't locate properties file");
properties = new Properties();
properties.load(is);
}
}
String property(final String key) {
return properties.getProperty(key);
}
}
and the /WEB-INF/app.properties :
upload.location=C:/_/
HTH and if you find a bug let me know

java.nio.file.NoSuchFileException When File.transferTo() is called

I've recently inherited a Java API and am having trouble with file uploads. Unfortunately, Java isn't a language I have much experience in so I'm a bit stumped by this.
The MultiPartFile is being received ok, and I can find the file in the temp directory, but when I try to use File.transferTo() to create the final file I just get the below error;
java.nio.file.NoSuchFileException: C:\Users\myUser\AppData\Local\Temp\undertow3706399294849267898upload -> S:\Dev\PolicyData\Temp.xlsx
As I mentioned the temp undertow file exists, and the directory on the S drive also exist, (but there's no Temp.xlsx as my understanding is this should be created by transferTo()). Any solutions I've found to this problem so far are resolved using absolute file paths.
This is a simplified version of the code but the error remains the same.
SpringBoot framework is "1.5.3.RELEASE", running Java 1.8.0_131
ResponseEntity handleFileUpload(#RequestPart(name = "file") MultipartFile file, #PathVariable Long stageFileTypeId) {
if (!file.isEmpty()) {
try {
String filePath = "S:\\Dev\\PolicyData\\Temp.xlsx";
log.info("Upload Path = {}", filePath);
File dest = new File(filePath);
file.transferTo(dest);
return ResponseUtil.wrapOrNotFound(Optional.ofNullable(filePath));
}
catch (Exception ex) {
log.error("An error has occurred uploading the file", ex);
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
}
}
else {
log.error("An error has occurred, no file was received");
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build();
}
}
If you need any more information please let me know.
Thanks,
Neil

The API for MultipartFile is a bit tricky. The transferTo(File) method javadoc states that (bold are mine):
This may either move the file in the filesystem, copy the file in the
filesystem, or save memory-held contents to the destination file. If
the destination file already exists, it will be deleted first.
If the target file has been moved in the filesystem, this operation
cannot be invoked again afterwards. Therefore, call this method just
once in order to work with any storage mechanism.
It seems that the Undertow implementantion already called it to move the in-memory uploaded file to "C:\Users\myUser\AppData\Loca\Temp\undertow3706399294849267898upload" so another transferTo is failing.
I came across the same problem using javax.servlet.http.Part in a Wildfly containter with Undertow.
If you are using Spring framework >= 5.1, you could try the Multipart.transferTo(Path) method, using dest.toPath()
Or you can copy from the inputStream, with something like this:
try (InputStream is = multipartFile.getInputStream()) {
Files.copy(is, dest.toPath());
}

Spring MVC upload a file and then provide a link for downloading

I have Spring MVC web app running on Tomcat.
I upload a file and save it in the /tmp folder on the file system.
Then I need to show a link to that file in the view (Thymeleaf), so that the user can download the file by clicking on the link. How to do that?
I've heard about configuring Tomcat to allow a specific context to link to a folder on the FS, but not sure how to do that or if that is the only solution. Please help.

The way I approach this is slightly different. Basically I use two controller actions for handling file uploads, one for uploading, and for downloading (viewing) files.
So upload action would save files to some preconfigured directory on the file system, I assume you already have that part working.
Then declare download action similar to this
#Controller
public class FileController {
#RequestMapping("/get-file/{filename}")
public void getFileAction(#RequestParam filename, HttpServletResponse response) {
// Here check if file with given name exists in preconfigured upload folder
// If it does, write it to response's output stream and set correct response headers
// If it doesn't return 404 status code
}
}
If you want to make impossible to download file just by knowing the name, after uploading file, save some meta info to the database (or any other storage) and assign some hash (random id) to it. Then, in getFileAction, use this hash to look for file, not the original filename.
Finally, I would discourage using /tmp for file uploads. It depends on the system/application used, but generally temp directory are meant, as name suggest, for temporary data. Usually it is guaranteed data in the temp directory will stay for "reasonable time", but applications must take into account that content of temp directory can be deleted anytime.

This is the precisely setup that worked for me (Tomcat 8, SpringMVC, boot):
server.xml:
<Context docBase="C:\tmp\" path="/images" />
In the controller:
public String createNewsSource(#ModelAttribute("newsSource") NewsSource source, BindingResult result, Model model,
#RequestParam("attachment") final MultipartFile attachment) {
new NewsSourceValidator().validate(source, result);
if (result.hasErrors()) {
return "source/addNewSource";
}
if (!attachment.isEmpty()) {
try {
byte[] bytes = attachment.getBytes();
BufferedOutputStream stream = new BufferedOutputStream(
new FileOutputStream(new File("/tmp/" + attachment.getOriginalFilename())));
stream.write(bytes);
stream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
source.setLogo("images/" + attachment.getOriginalFilename());
newsSourceService.createNewsSourceIfNotExist(source);
return "redirect:/sources/list";
}
As you can see I am saving the file to /tmp, but in the DB (source.setLogo()), I am pointing to images as mapped in server.xml
Here's where I found about Tomcat config:
If the images are all located outside the webapp and you want to have
Tomcat's DefaultServlet to handle them, then all you basically need to
do in Tomcat is to add the following Context element to
/conf/server.xml inside tag:
This way they'll be accessible through http://example.com/images/....
SO answer to a similar question

Webapplication: Delete files during runtime

I am developing a webapp (for mobile phones). There is one xhtml page, where I want to show a picture, which is stored locally on my hard drive (for example: D:\pictures\test.jpg).
Since browsers block images when they are located on a local harddrive, I wrote a method in my javabean, where the picture, stored on the localHD, is copied to the webApp directory, when the user enters the xhtml page. After the user leaves the page, the copied file inside the webapp should be deleted.
So when I'm running my app, copying works perfectly and the pictures are displayed correctly. However, when the files should get deleted, I get this errormessage:
java.nio.file.FileSystemException: D:\WebAppPath\src\main\webapp\resources\pics\test.jpg:
The process cannot be accessed because the file is being used by another process.
Strangely enough, after stopping and restarting the application I can delete the same image if it is still in the webApp directory. (But Only once; after re-copying it, I get the error message again.)
Also if I want to delete the file manually, by using Windows explorer, I get the error message that the file can't be deleted because it is used by Java(TM) Platform SE Binary.
So to delete the file (manually or via the bean) I have to wait for a restart of the application, which of course is not an acceptable solution for the end user.
I'm using JSF2.0 with Primefaces and Primefaces Mobile components. My IDE is Netbeans and I use Spring Webflow framework to navigate and trigger actions/methods between the xhtml pages.
Here's the code for the copying method in my JavaBean:
public void copyFotoToLocalhost() {
if (fotoList.size() > 0) {
for (int i = 0; i < fotoList.size(); i++) {
Foto tempPic = fotoList.get(i);
String tempItemName = tempPic.getItemName();
String originalFile = "D:\\localFilepath\\" + tempItemName;
String tempFileName = "D:\\WebAppPath\\src\\main\\webapp\\resources\\pics\\" + tempItemName;
File existTest = new File(tempFileName);
if (existTest.exists() == false) {
try {
File orFile = new File(originalFile);
File tempFile = new File(tempFileName);
InputStream in = new FileInputStream(orFile);
OutputStream out = new FileOutputStream(tempFile);
byte[] buf = new byte[8192];
int len;
while ((len = in.read(buf)) > 0) {
out.write(buf, 0, len);
}
in.close();
out.close();
tempFile.setWritable(true);
System.out.println("File copied.");
} catch (FileNotFoundException ex) {
System.out.println(ex.getMessage() + " in the specified directory.");
System.exit(0);
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
}
}
}
Here's the code for the delete method:
public void deleteFotos() {
if (fotoList.size() > 0) {
for (int i = 0; i < fotoList.size(); i++) {
Foto tempPic = fotoList.get(i);
String tempItemName = tempPic.getItemName();
Path tempLocation = Paths.get("D:\\webAppPath\\src\\main\\webapp\\resources\\pics\\" + tempItemName);
fotoList.remove(i);
i--;
try {
Files.deleteIfExists(tempLocation);
System.out.println("sucessfully deleted" + tempPic.getItemName());
} catch (IOException ex) {
Logger.getLogger(WundDokuBean.class.getName()).log(Level.SEVERE, null, ex);
System.out.println("Fail # " + tempPic.getItemName());
}
}
fotoList.clear();
}
Do you have an idea, how to fix this?
I hope you understand my problem, if not please tell me which information you need, I'll try to provide it.

There is one xhtml page, where I want to show a picture, which is stored locally on my hard drive (for example: D:\pictures\test.jpg). Since browsers block images when they are located on a local harddrive (...)
I want to clear out a conceptual misunderstanding first: You seem to expect that it would work fine when the browser wouldn't have blocked it. This is completely untrue. You seem to expect that images are inlined in the HTML output. No, they are downloaded individually and independently from the HTML page. If you had continued to use local disk file system paths, then it would have worked only and only if your webpage visitor has also exactly the same file at exactly the same location at their disk file system. In reality, this is obviously not the case. It would only work if both the webbrowser and webserver runs at physically the same machine.
Coming back to your concrete problem of being unable to delete the file, it's is caused because the servletcontainer usually locks the files in expanded WAR folder. I can't tell the exact reason, but that's not relevant here as this whole approach is wrong anyway. This approach would fail when the deployed WAR file is not expanded on disk file system, but instead in server's memory. Also, hardcoding environment-specific disk file system paths is a bad idea. You'd need to edit, rewrite, recompile, rebuild the whole WAR everytime you change the environment. In other words, your webapp is not portable.
You need to keep the files there where they originally are and make them publicly available by a real URL. This can be achieved in 2 general ways:
Add a virtual host to the server config, pointing to D:\localFilepath\. How to achieve that depends on the server used. You didn't tell anything about the server make/version used, but using Spring suggests that you're not being able to use full Java EE stack and are likely using a barebones JSP/Servlet container such as Tomcat. In that case, it's a matter of adding the following line to its /conf/server.xml:
<Context docBase="D:\localFilepath" path="/fotos" />
This way they are available by http://localhost:8080/fotos/*.
Create a servlet which reads files from D:\localFilepath and writes to HTTP response. With Servlet 3.0 and Java 7 it's really a breeze. Here's a kickoff example (nullchecks/file-exist-checks/doHead()/caching/resuming omitted for brevity):
#WebServlet("/fotos/*")
public class FotosServlet extends HttpServlet {
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletExcpetion, IOException {
File file = new File("D:/localFilepath", request.getPathInfo().substring(1));
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName()));
response.setHeader("Content-Length", String.valueOf(file.length()));
Files.copy(file.toPath(), response.getOutputStream());
}
}
That's basically it. This way they're available on http://localhost:8080/contextname/fotos/*.

REST - Why generated excel file is not actually created when tried as web application?

I created simple REST web app that would create Excel file and put into current directory.
But somehow the generated excel is not in the directory. Actually it is not even being created.
The output "done" is shown in GlassFish server log so the process actually get to the end without any error. The only thing I am suspecting is the file path I'm specifying for "myExcelFileThatWouldNotShowUp".
I gave full path or relative path I can think of but Excel file is not still showing up.
Interestingly, if I don't run this as web app (i.e. put the code in local main() function and run it, it works)
Thus I think something to do with GlassFish but can't really figure out :(
GlassFish v3
REST / JAX-RS
Excella framework to generate Excel spreadsheet from template (myTemplate.xls)
Code snippet
#Path("horizontalProcess")
#GET
#Produces("application/xml")
public String getProcessHorizontally() {
try {
URL templateFileUrl = this.getClass().getResource("myTemplate.xls");
// getPath() outputs...
// /C:/Users/m-takayashiki/Documents/NetBeansProjects/KogaAlpha/build/web/WEB-INF/classes/local/test/jaxrs/myTemplate.xls
System.out.println(templateFileUrl.getPath());
String templateFilePath = URLDecoder.decode(templateFileUrl.getPath(), "UTF-8");
//specify output path which is current dir and should create
//myExcelFileThatWouldNotShowup.xls but it is not..
String outputFileDir = "myExcelFileThatWouldNotShowUp";
//<<template path>>, <<output path>>, <<file format>>
ReportBook outputBook = new ReportBook(templateFilePath, outputFileDir, ExcelExporter.FORMAT_TYPE);
ReportSheet outputSheet = new ReportSheet("myExcelSheet");
outputBook.addReportSheet(outputSheet);
//this is printed out so process actually gets here
System.out.println("done!!");
}
catch(Exception e) {
System.out.println(e);
}
return null;
}//end method

That's why one shouldn't code when tired/overtime worked....
I forgot to add 2 lines of code at the end that actually generate the excel...
cost me couple hours of debugging.. (don't ask how i was debugging :p
ReportProcessor reportProcessor = new ReportProcessor();
reportProcessor.process(outputBook);
Btw, generated file are stored in the dir below as default if you don't specify.
//C:\Users\m-takayashiki\.netbeans\6.9\config\GF3\domain1