In my web application I have to send email to set of predefined users like [email protected]
, so I wish to add that to a .properties
file and access it when required. Is this a correct procedure, if so then where should I place this file? I am using Netbeans IDE which is having two separate folders for source and JSP files.
It's your choice. There are basically three ways in a Java web application archive (WAR):
So that you can load it by ClassLoader#getResourceAsStream()
with a classpath-relative path:
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("foo.properties");
// ...
Properties properties = new Properties();
properties.load(input);
Here foo.properties
is supposed to be placed in one of the roots which are covered by the default classpath of a webapp, e.g. webapp's /WEB-INF/lib
and /WEB-INF/classes
, server's /lib
, or JDK/JRE's /lib
. If the propertiesfile is webapp-specific, best is to place it in /WEB-INF/classes
. If you're developing a standard WAR project in an IDE, drop it in src
folder (the project's source folder). If you're using a Maven project, drop it in /main/resources
folder.
You can alternatively also put it somewhere outside the default classpath and add its path to the classpath of the appserver. In for example Tomcat you can configure it as shared.loader
property of Tomcat/conf/catalina.properties
.
If you have placed the foo.properties
it in a Java package structure like com.example
, then you need to load it as below
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
InputStream input = classLoader.getResourceAsStream("com/example/foo.properties");
// ...
Note that this path of a context class loader should not start with a /
. Only when you're using a "relative" class loader such as SomeClass.class.getClassLoader()
, then you indeed need to start it with a /
.
ClassLoader classLoader = getClass().getClassLoader();
InputStream input = classLoader.getResourceAsStream("/com/example/foo.properties");
// ...
However, the visibility of the properties file depends then on the class loader in question. It's only visible to the same class loader as the one which loaded the class. So, if the class is loaded by e.g. server common classloader instead of webapp classloader, and the properties file is inside webapp itself, then it's invisible. The context class loader is your safest bet so you can place the properties file "everywhere" in the classpath and/or you intend to be able to override a server-provided one from the webapp on.
So that you can load it by ServletContext#getResourceAsStream()
with a webcontent-relative path:
InputStream input = getServletContext().getResourceAsStream("/WEB-INF/foo.properties");
// ...
Note that I have demonstrated to place the file in /WEB-INF
folder, otherwise it would have been public accessible by any webbrowser. Also note that the ServletContext
is in any HttpServlet
class just accessible by the inherited GenericServlet#getServletContext()
and in Filter
by FilterConfig#getServletContext()
. In case you're not in a servlet class, it's usually just injectable via @Inject
.
So that you can load it the usual java.io
way with an absolute local disk file system path:
InputStream input = new FileInputStream("/absolute/path/to/foo.properties");
// ...
Note the importance of using an absolute path. Relative local disk file system paths are an absolute no-go in a Java EE web application. See also the first "See also" link below.
Just weigh the advantages/disadvantages in your own opinion of maintainability.
If the properties files are "static" and never needs to change during runtime, then you could keep them in the WAR.
If you prefer being able to edit properties files from outside the web application without the need to rebuild and redeploy the WAR every time, then put it in the classpath outside the project (if necessary add the directory to the classpath).
If you prefer being able to edit properties files programmatically from inside the web application using Properties#store()
method, put it outside the web application. As the Properties#store()
requires a Writer
, you can't go around using a disk file system path. That path can in turn be passed to the web application as a VM argument or system property. As a precaution, never use getRealPath()
. All changes in deploy folder will get lost on a redeploy for the simple reason that the changes are not reflected back in original WAR file.