args4j - Command Line Argument with Annotaion

args4j
หนุ่มญี่ปุ่นคนนี้มี idea ในการเอา Annotaion มาใช้ได้เหมาะมาก
ลองดูตัวอย่าง code เขา

import org.kohsuke.args4j.Argument;
import org.kohsuke.args4j.CmdLineException;
import org.kohsuke.args4j.CmdLineParser;
import org.kohsuke.args4j.Option;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;


/**
 * Sample program that shows how you can use args4j.
 * 
 * @author
 *      Kohsuke Kawaguchi (kk@kohsuke.org)
 */
public class SampleMain {
    
    @Option(name="-r",usage="recursively run something")
    private boolean recursive;

    @Option(name="-o",usage="output to this file",metaVar="OUTPUT")
    private File out = new File(".");

    @Option(name="-str")        // no usage
    private String str = "(default value)";

    @Option(name="-n",usage="repeat <n> times\nusage can have new lines in it an
d also it can be verrrrrrrrrrrrrrrrrry long")
    private int num = -1;

    // receives other command line parameters than options
    @Argument
    private List<String> arguments = new ArrayList<String>();

    public static void main(String[] args) throws IOException {
        new SampleMain().doMain(args);
    }
    
    public void doMain(String[] args) throws IOException {
        CmdLineParser parser = new CmdLineParser(this);

        try {
            // parse the arguments.
            parser.parseArgument(args);
            
            // you can parse additional arguments if you want.
            // parser.parseArgument("more","args");
            
            // after parsing arguments, you should check
            // if enough arguments are given.
            if( arguments.isEmpty() )
                throw new CmdLineException("No argument is given");
            
        } catch( CmdLineException e ) {
            // if there's a problem in the command line,
            // you'll get this exception. this will report
            // an error message.
            System.err.println(e.getMessage());
            System.err.println("java SampleMain [options...] arguments...");
            parser.printUsage(System.err);
            return;
        }
        
        // this will redirect the output to the specified output
        System.out.println(out);

        if( recursive )
            System.out.println("-r flag is set");
        
        System.out.println("-str was "+str);

        if( num>=0 )
            System.out.println("-n was "+num);
        
        // access non-option arguments
        System.out.println("other arguments are:");
        for( String s : arguments )
            System.out.println(s);
    }
}

เทียบกับ jakarta common CLI

// create the command line parser
CommandLineParser parser = new PosixParser();

// create the Options
Options options = new Options();
options.addOption( "a", "all", false, "do not hide entries starting with ." );
options.addOption( "A", "almost-all", false, "do not list implied . and .." );
options.addOption( "b", "escape", false, "print octal escapes for nongraphic "
                                         + "characters" );
options.addOption( OptionBuilder.withLongOpt( "block-size" )
                                .withDescription( "use SIZE-byte blocks" )
                                .withValueSeparator( '=' )
                                .hasArg()
                                .create() );
options.addOption( "B", "ignore-backups", false, "do not list implied entried "
                                                 + "ending with ~");
options.addOption( "c", false, "with -lt: sort by, and show, ctime (time of last
 " 
                               + "modification of file status information) with 
"
                               + "-l:show ctime and sort by name otherwise: sort
 "
                               + "by ctime" );
options.addOption( "C", false, "list entries by columns" );

String[] args = new String[]{ "--block-size=10" };

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

    // validate that block-size has been set
    if( line.hasOption( "block-size" ) ) {
        // print the value of block-size
        System.out.println( line.getOptionValue( "block-size" ) );
    }
}
catch( ParseException exp ) {
    System.out.println( "Unexpected exception:" + exp.getMessage() );
}