JarCastingjava-flags
Light-weight command-line flags using an easy-to-use static binding approach. It provides annotations to describe classes and flags and tools to generate program usage documentation from sources at runtime.
Usage
To use a command-line flag value you need to create an accessor for it. This is done by Flags.create() method or by one of the specific variants:
class ReadmeExample {
static final Flag<String> input = Flags.create("");
}
The name argument must match the flag name as specified on command-line (without '--' prepended), i.e.:
java ProgramRunner --input input.txt
In your program main() method pass the command-line arguments to Flags:
public class ProgramRunner {
public static main(String[] args) {
Flags.parse(args, ImmutableList.of("com.github.yin.flags.example"));
// ....
}
}
To access the flag value, use the accessor get() method. This is typically done in the constructor, or in a Guice Module Provider:
public class ReadmeExample {
static final Flag<String> input = Flags.create("");
private final String inputfile;
// ...
ReadmeExample() {
this.inputfile = input.get();
}
}
Generating command-line usage help
And finally, to attach some docs and generate the documentation, you just use the @FlagDesc annotation:
@FlagDesc("This class is an example how to print files")
public class ReadmeExample {
@FlagDesc("Specifies path to input file")
static final Flag<String> input = Flags.create("");
// ...
}
... and call the printUsage() method for you program package:
@FlagDesc("This class is an example how to print files")
public class ReadmeExample {
// ...
public static void main(String[] args) {
try {
Flags.parse(args, ImmutableList.of("com.github.yin.flags.example"));
} catch (Flags.ParseException e) {
System.err.println(e.getMessage());
Flags.printUsage("com.github.yin.flags.example");
System.exit(1);
return;
}
ReadmeExample re = new ReadmeExample();
re.run();
}
// ...
}
Validators
public class ProgramRunner {
static final Flag<String> input = Flags.create("")
.validator((String path) -> {
if (path == null || path.isEmpty()) {
throw new Flags.ParseException("Input path is empty");
}
});
}
Installation
Just grab the package from Maven Central:
<dependency>
<groupdId>com.github.yin.flags</groupId>
<artifactId>java-flags</artifactId>
<version>0.3.0-beta1</version>
</dependency>
Building
Easy, use this GitHub repository and Maven:
git clone https://github.com/yin/java-flags.git java-flags
cd !$
mvn install
License
MIT License, (C) 2016-2017 Matej 'Yin' Gagyi