Apache commons CLI not parsing as expected?

Question

public static void main(String[] args) {

    Options options = new Options();
    Option hostOption = Option.builder("h")
            .longOpt("host")
            .required(false)
            .build();

    Option portOption = Option.builder("p")
            .longOpt("port")
            .required(false)
            .type(Number.class)
            .build();

    Option serviceNameOption = Option.builder("n")
            .longOpt("service_name")
            .required(false)
            .build();

    options.addOption(hostOption);
    options.addOption(portOption);
    options.addOption(serviceNameOption);

    String serviceName = "dbservice"
    String host = "localhost";
    int port = 7512;
    CommandLineParser parser = new DefaultParser();
    Server server = new Server();
    try {
        CommandLine cmd = parser.parse(options, args);
        if(cmd.hasOption("host")) {
            host = cmd.getOptionValue("host");
            System.out.println(host); //gets in here but prints null
        }
        if (cmd.hasOption("port")) {
            port = ((Number)cmd.getParsedOptionValue("port")).intValue();
            System.out.println(port); // gets in here but throws a null pointer exception

        }
        if (cmd.hasOption("service_name")) {
            serviceName = cmd.getOptionValue("service_name");
            System.out.println(serviceName); // gets in here but prints null
        }
    } catch(Exception e) {}
 }

I am using Apache commons cli library to parse command line args however it doesn't seem to parse as expected. Not sure what I am missing here?

I invoked in many different way just to see if it works and the below is one of them java -jar dbservice.jar --host localhost --port 7514. What is the right way to invoke anyway? I dont see that in the documentation

Answer 1

In order for the Option to accept an argument, the hasArg(true) must be passed to the builder. For each of the options, add a ".hasArg(true)". Modifying your code with this argument and running a test case resulted in the expected output.

    Option hostOption = Option.builder("h")
        .longOpt("host")
        .required(false)
        .hasArg(true)
        .build();