Question

I am using args4j to parse the arguments given to my program.

Here is the code where I define 2 arguments of Date type. The handler just parses the given date and throws a CommandLineException if the date is malformed.

@Option(name="-b", metaVar="<beginDate>", handler=DateOptionHandler.class, usage="...")
private Date beginDate;

@Option(name="-e", metaVar="<endDate>", handler=DateOptionHandler.class, usage="...")
private Date endDate;

I need to be able to return a different code (int value) if it is beginDate or endDate which throws an exception.

Currently, my main method looks like this :

CmdLineParser parser = new CmdLineParser(this);
parser.setUsageWidth(120);

try {
    parser.parseArgument(args);
} catch (CmdLineException e) {
    /* Print usage if an error occurs during the parsing */
    System.err.println(e.getMessage());
    System.err.println("Usage : java LaunchProgram [options]");
    e.getParser().printUsage(System.err);

    /* What I need to do : */
    if(optionWhichThrewTheException.equals("-b") return 2;
    if(optionWhichThrewTheException.equals("-e") return 3;

    /* Other arguments */
    return -1;
}

But I can’t figure out how I can know which argument threw the exception (I looked the CmdLineException methods, but I found nothing).

Is there a way to obtain the parameter which can not be parsed ?

Thanks by advance for your help.

Answer 1

I’ve never used args4j, but looking at its documentation, it seems that the exception is thrown by the option handler. So, use a BDateOptionHandler and a EDateOptionHandler, that throw a custom subclass of CmdLineException containing the needed information:

public class BDateOptionHandler extends DateOptionHandler {
    @Override
    public int parseArguments(Parameters params) throws CmdLineException {
        try {
            super.parseArguments(params);
        }
        catch (CmdLineException e) {
            throw new ErrorCodeCmdLineException(2);
        }
    }
}

public class EDateOptionHandler extends DateOptionHandler {
    @Override
    public int parseArguments(Parameters params) throws CmdLineException {
        try {
            super.parseArguments(params);
        }
        catch (CmdLineException e) {
            throw new ErrorCodeCmdLineException(3);
        }
    }
}

...
try {
    parser.parseArgument(args);
} 
catch (CmdLineException e) {
    ...
    if (e instanceof ErrorCodeCmdLineException) {
        return ((ErrorCodeCmdLineException) e).getErrorCode();
    }
}