Java System properties
System properties can be set on the Java command line using the -Dpropertyname=value syntax. They can also be added at Clojure runtime using (System/getProperties) will return a Properties object with the system properties for the current REPL.
Properties are often defined in a *.properties file to configure the environment in containerized deployment processes. For example, the version of Java used in Heroku containers is set by adding java.runtime.version=11 property to a system.properties file.
Commonly used properties
Java Runtime
Description
java.home
JRE home directory
java.library.path
JRE library search path for search native libraries (usually taken from PATH environment variable)
java.class.path
JRE classpath e.g., '.' (dot – used for current working directory).
java.ext.dirs
JRE extension library path(s)
java.version
JDK version
java.runtime.version
JRE version
File system
Description
file.separator
symbol for file directory separator ('/' for Unix or '\' for windows)
path.separator
symbol for separating path entries in PATH or CLASSPATH. (':' for Unix or ';' for windows)
line.separator
symbol for end-of-line / new line ("\n" for Unix or "\r\n" for windows) or /Mac OS X.
User system
Description
user.name
the user’s name.
user.home
the user’s home directory.
user.dir
the user’s current working directory
Operating System
Description
os.name
operating System name
os.version
operating System version
os.arch
operating System architecture
Examining the system properties
Evaluating (System/getProperties) on an Ubuntu Linux operating system running Java 11 and Spacemacs with CIDER returned the following properties.