The following code grants me access to a specific PNG resource within my project:
BufferedImage temp = ImageIO.read(Thread.currentThread().getContextClassLoader().getResource("play.png"));
However, I have n images that I don't have to have to hardcode ("play.png", "pause.png", etc); without having an external image library (which I would simply loop through with File), is there a way to get all images within the project?
Ideally, all files within a specific source folder, really. Or source folders. getResources only seems to work for multiples of a specific named resource, which isn't what I want.
EDIT:
To be clear, this is a local project / application; it isn't intended to be a servlet or otherwise deployed on the Web. Question updated with the offline tag in case this is applicable.
You can do something like this.Here I am trying to get all the images in a folder named images in a servlet.
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String pathToImages = getServletContext().getRealPath("/images");
File[] files = new File(pathToImages).listFiles();
showImages(files);
}
public static void showImages(File[] files) {
for (File file : files) {
System.out.println("File: " + file.getName());
}
}
Related
I have written a project where some images are used for the application's appearance and some text files will get created and deleted along the process. I only used the absolute path of all used files in order to see how the project would work, and now that it is finished I want to send it to someone else. so what I'm asking for is that how I can link those files to the project so that the other person doesn't have to set those absolute paths relative to their computer. something like, turning the final jar file with necessary files into a zip file and then that the person extracts the zip file and imports jar file, when runs it, the program work without any problems.
by the way, I add the images using ImageIcon class.
I'm using eclipse.
For files that you just want to read, such as images used in your app's icons:
Ship them the same way you ship your class files: In your jar or jmod file.
Use YourClassName.class.getResource or .getResourceAsStream to read these. They are not files, any APIs that need a File object can't work. Don't use those APIs (they are bad) - good APIs take a URI, URL, or InputStream, which works fine with this.
Example:
package com.foo;
public class MyMainApp {
public void example() {
Image image = new Image(MyMainApp.class.getResource("img/send.png");
}
public void example2() throws IOException {
try (var raw = MyMainApp.class.getResourceAsStream("/data/countries.txt")) {
BufferedReader in = new BufferedReader(
new InputStreamReader(raw, StandardCharsets.UTF_8));
for (String line = in.readLine(); line != null; line = in.readLine()) {
// do something with each country
}
}
}
}
This class file will end up in your jar as /com/foo/MyMainApp.class. That same jar file should also contain /com/foo/img/send.png and /data/countries.txt. (Note how starting the string argument you pass to getResource(AsStream) can start with a slash or not, which controls whether it's relative to the location of the class or to the root of the jar. Your choice as to what you find nicer).
For files that your app will create / update:
This shouldn't be anywhere near where your jar file is. That's late 80s/silly windows thinking. Applications are (or should be!) in places that you that that app cannot write to. In general the installation directory of an application is a read-only affair, and most certainly should not be containing a user's documents. These should be in the 'user home' or possibly in e.g. `My Documents'.
Example:
public void save() throws IOException {
Path p = Paths.get(System.getProperty("user.home"), "navids-app.save");
// save to that file.
}
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
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
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
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