Reading and Writing a Properties File

// Read properties file.
Properties properties = new Properties();
try {
properties.load(new FileInputStream("filename.properties"));
} catch (IOException e) { }

// Write properties file.
try {
properties.store(new FileOutputStream("filename.properties"), null);
} catch (IOException e) { }

To read java properties files from the classpath:

The properties files can be stored in the classpath. This way they can be put inside jar files and it’s really useful for web applications when the absolute location of the properties files is not known. When I tested this in an web application it didn’t work:

Properties properties = new Properties() ;
URL url =  ClassLoader.getSystemResource("test.properties");
properties.load(new FileInputStream(new File(url.getFile())));

To read java properties files from the classpath in a web application:

The following example works to load the properties files in a web application. This snippet was tested on Tomcat 5.5. The ‘/’ represents the root of the class path. Otherwise the properties file location is considered relatively to “this” class (or to MyClass for the second example):

Properties properties = new Properties() ;
properties.load(this.getClass().getResourceAsStream("/seoimproved.properties"));

Similar example to use in a static context:

Properties properties = new Properties() ;
properties.load(MyClass.class.getResourceAsStream("/seoimproved.properties"));

To read java properties files from a specific location:

The properties files can be loaded from any location.

Properties properties = new Properties() ;
properties.load(new FileInputStream("C:\\tmp\\test.properties"));