In the following snippet:
ServletContext context = request.getServletContext();
String path = context.getRealPath("/");
What does /
in the method getRealPath()
represent? When should I use it?
The ServletContext#getRealPath()
is intented to convert a web content path (the path in the expanded WAR folder structure on the server's disk file system) to an absolute disk file system path.
The "/"
represents the web content root. I.e. it represents the web
folder as in the below project structure:
YourWebProject
|-- src
| :
|
|-- web
| |-- META-INF
| | `-- MANIFEST.MF
| |-- WEB-INF
| | `-- web.xml
| |-- index.jsp
| `-- login.jsp
:
So, passing the "/"
to getRealPath()
would return you the absolute disk file system path of the /web
folder of the expanded WAR file of the project. Something like /path/to/server/work/folder/some.war/
which you should be able to further use in File
or FileInputStream
.
Note that most starters don't seem to see/realize that you can actually pass the whole web content path to it and that they often use
String absolutePathToIndexJSP = servletContext.getRealPath("/") + "index.jsp"; // Wrong!
or even
String absolutePathToIndexJSP = servletContext.getRealPath("") + "index.jsp"; // Wronger!
instead of
String absolutePathToIndexJSP = servletContext.getRealPath("/index.jsp"); // Right!
Also note that even though you can write new files into it using FileOutputStream
, all changes (e.g. new files or edited files) will get lost whenever the WAR is redeployed; with the simple reason that all those changes are not contained in the original WAR file. So all starters who are attempting to save uploaded files in there are doing it wrong.
Moreover, getRealPath()
will always return null
or a completely unexpected path when the server isn't configured to expand the WAR file into the disk file system, but instead into e.g. memory as a virtual file system.
getRealPath()
is unportable; you'd better never use itUse getRealPath()
carefully. There are actually no sensible real world use cases for it. Based on my 20 years of Java EE experience, there has always been another way which is much better and more portable than getRealPath()
.
If all you actually need is to get an InputStream
of the web resource, better use ServletContext#getResourceAsStream()
instead, this will work regardless of the way how the WAR is expanded. So, if you for example want an InputStream
of index.jsp
, then do not do:
InputStream input = new FileInputStream(servletContext.getRealPath("/index.jsp")); // Wrong!
But instead do:
InputStream input = servletContext.getResourceAsStream("/index.jsp"); // Right!
Or if you intend to obtain a list of all available web resource paths, use ServletContext#getResourcePaths()
instead.
Set<String> resourcePaths = servletContext.getResourcePaths("/");
You can obtain an individual resource as URL
via ServletContext#getResource()
. This will return null
when the resource does not exist.
URL resource = servletContext.getResource(path);
Or if you intend to save an uploaded file, or create a temporary file, then see the below "See also" links.
A web application's context path is the directory that contains the web application's WEB-INF directory. It can be thought of as the 'home' of the web app. Often, when writing web applications, it can be important to get the actual location of this directory in the file system, since this allows you to do things such as read from files or write to files.
This location can be obtained via the ServletContext object's getRealPath() method. This method can be passed a String parameter set to File.separator to get the path using the operating system's file separator ("/" for UNIX, "\" for Windows).
There is also a change between Java 7 and Java 8. Admittedly it involves the a deprecated call, but I had to add a "/" to get our program working! Here is the link discussing it Why does servletContext.getRealPath returns null on tomcat 8?
My Method:
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
String path = request.getRealPath("/WEB-INF/conf.properties");
Properties p = new Properties();
p.load(new FileInputStream(path));
String StringConexion=p.getProperty("StringConexion");
String User=p.getProperty("User");
String Password=p.getProperty("Password");
}
catch(Exception e){
String msg = "Excepcion " + e;
}
}
WebApplicationContext
. e.g. You have application named asTestWebApp
then/
would give path tillTestWebApp
– Dhruvenkumar Shah