javacommand-line-interfaceapache-commons-cli

Java Apache CLI Optional Command Line Arguments not working


Trying to use Apache Commons Command Line Interface 1.3.1 from here It works fine for required arguments, but seems to drop any optional arguments. Can anyone spot a problem with my code below?

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.DefaultParser;
import org.apache.commons.cli.Option;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;

public class TestCommandLine {

    public static void main(String[] args) {

        // *****  test with command line arguments -R myfirstarg -O mysecondarg  *****
        // *****  the second arg is not being captured                          *****

        System.out.println("Number of Arguments : " + args.length);

        String commandline = "";
        for (String arg : args) {
            commandline = commandline + (arg + " ");
        }
        commandline.trim();
        System.out.println("Command-line arguments: " + commandline);

        // create Options object
        Options options = new Options();
        options.addOption("R", true, "Enter this required argument");
        Option optionalargument = Option.builder("O")
                .optionalArg(true)   // if I change this line to .hasArg(true) it works, but then is not optional
                .desc("Enter this argument if you want to")
                .build();
        options.addOption(optionalargument);

        // initialize variables used with command line arguments
        String firstargument = null;
        String secondargument = null;


        CommandLineParser parser = new DefaultParser();
        try {
            // parse the command line arguments
            CommandLine cmd = parser.parse( options, args );

            firstargument = cmd.getOptionValue("R");
            secondargument = cmd.getOptionValue("O");

            if(cmd.hasOption("R")){
                if(firstargument == null){
                    System.out.println("Must provide the first argument  ...  exiting...");
                    System.exit(0);
                }
                else {
                    System.out.println("First argument is " + firstargument);
                }
            }
            if(cmd.hasOption("O")) {
                // optional argument
                if (secondargument == null){
                    System.out.println("Second argument is NULL");
                }
                else{
                    // should end up here if optional argument is provided, but it doesn't happen
                    System.out.println("Second argument is " + secondargument);
                }
            }

        }
        catch( ParseException exp ) {
            // oops, something went wrong
            System.err.println( "Parsing failed.  Reason: " + exp.getMessage() );
        }
    }

}

The output from the above code is:

Number of Arguments : 4
Command-line arguments: -R myfirstarg -O mysecondarg 
First argument is myfirstarg
Second argument is NULL

Why isn't "mysecondarg" being captured? If I change the line .optionalArg(true) to .hasArg(true), then the second argument is captured, but the whole idea is to be able to optionally leave the second argument out.


Solution

  • It seems you need to set numberOfArgs in addition to hasOptionalArgs in order for it to work properly.