Reading properties file from JAR directory

Question

I'm creating an executable JAR that will read in a set of properties at runtime from a file. The directory structure will be something like:

/some/dirs/executable.jar
/some/dirs/executable.properties

Is there a way of setting the property loader class in the executable.jar file to load the properties from the directory that the jar is in, rather than hard-coding the directory.

I don't want to put the properties in the jar itself as the properties file needs to be configurable.

Answer 1

Why not just pass the properties file as an argument to your main method? That way you can load the properties as follows:

public static void main(String[] args) throws IOException {
  Properties props = new Properties();
  props.load(new BufferedReader(new FileReader(args[0])));
  System.setProperties(props);
}

The alternative: If you want to get the current directory of your jar file you need to do something nasty like:

CodeSource codeSource = MyClass.class.getProtectionDomain().getCodeSource();
File jarFile = new File(codeSource.getLocation().toURI().getPath());
File jarDir = jarFile.getParentFile();

if (jarDir != null && jarDir.isDirectory()) {
  File propFile = new File(jarDir, "myFile.properties");
}

... where MyClass is a class from within your jar file. It's not something I'd recommend though - What if your app has multiple MyClass instances on the classpath in different jar files (each jar in a different directory)? ie You can never really guarantee that MyClass was loaded from the jar you think it was.

Answer 2

 public static void loadJarCongFile(Class Utilclass ) { try{ String path= Utilclass.getResource("").getPath(); path=path.substring(6,path.length()-1); path=path.split("!")[0]; System.out.println(path); JarFile jarFile = new JarFile(path); final Enumeration<JarEntry> entries = jarFile.entries(); while (entries.hasMoreElements()) { final JarEntry entry = entries.nextElement(); if (entry.getName().contains(".properties")) { System.out.println("Jar File Property File: " + entry.getName()); JarEntry fileEntry = jarFile.getJarEntry(entry.getName()); InputStream input = jarFile.getInputStream(fileEntry); setSystemvariable(input); InputStreamReader isr = new InputStreamReader(input); BufferedReader reader = new BufferedReader(isr); String line; while ((line = reader.readLine()) != null) { System.out.println("Jar file"+line); } reader.close(); } } } catch (Exception e) { System.out.println("Jar file reading Error"); } } public static void setSystemvariable(InputStream input) { Properties tmp1 = new Properties(); try { tmp1.load(input); for (Object element : tmp1.keySet()) { System.setProperty(element.toString().trim(), tmp1.getProperty(element.toString().trim()).trim()); } } catch (IOException e) { System.out.println("setSystemvariable method failure"); } }