使用命令行参数加载属性文件-Java

Question

What is the best way to load a property file when path to the property file is not fixed and provided via command line arguments?

I am using the following code to load it but it is giving me null pointer exception when run using command line arguments:

Properties p = new Properties();        
p.load(testClass.class.getResourceAsStream("path to the property file"));

Answer 1

If you get the (full) path via command line, you jsut need to provide a reader or input stream with that path. In the end, your code could look like this:

    public static void main(String[] args) {
            System.out.println("reading property file " + args[0]);

            // create new initial properties
            Properties properties = new Properties();
            // open reader to read the properties file
            try (FileReader in = new FileReader(args[0])){
                // load the properties from that reader
                properties.load(in);
            } catch (IOException e) {
                // handle the exception
                e.printStackTrace();
            }

            // print out what you just read
            Enumeration<?> propertyNames = properties.propertyNames();
            while(propertyNames.hasMoreElements()) {
                String name = propertyNames.nextElement().toString();
                System.out.println(name + ": " + properties.getProperty(name));
            }
        }