Piccolo CLI Library

This is a lightweight and friendly library to add a command line interface to a Java program. Just provide one or more "handler" classes with public methods annotated with @Command and the library will allow users to call them from the console.

Basic Usage

Create a handler class as below:

public class DemoHandler {

	@Command
	public void hello() {

		System.out.println("Hello World!");

	}

}

Pass an instance the handler class to a Console object:

public static void main(String[] args) {

	Console c = new Console().addHandler(new DemoHandler());

	c.run();

}

This will generate the following console:

______  _                     _
| ___ \(_)                   | |
| |_/ / _   ___   ___   ___  | |  ___
|  __/ | | / __| / __| / _ \ | | / _ \
| |    | || (__ | (__ | (_) || || (_) |
\_|    |_| \___| \___| \___/ |_| \___/


Type :l for a list of available commands or :q to quit

>> :l
There are 4 available commands:
:list (aliases: :l)
:quit (aliases: :q)
:type (aliases: :t)
hello

>> hello
Hello World!

>>

(:l is an internal command used to list available commands.)

Command Arguments

Haskell-style arguments can be added after the command name, for example:

@Command
public void add(int a, int b) {

	System.out.printf("%d + %d = %d\n", a, b, a + b);

}

>> add 3 5
3 + 5 = 8

All primitive data types are supported.

Alternatively, the method can receive an ArrayList<String> object containing the parameters as in:

@Command
public void sum(String[] args) {

	int total = 0;

	for (String s : args)
		total = total + Integer.valueOf(s);

	System.out.println(total);

}

>> sum 3 7 18
28

@Command Annotations

The @Command annotation can be used to specify command aliases:

@Command(aliases = { "perf", "compute" })
public void performComplexComputations(String[] args) {

	// do stuff

}

When one or more aliases are defined the method cannot be called by its Java name. For the above code:

>> :l
There are 4 available commands:
:list (aliases: :l)
:quit (aliases: :q)
:type (aliases: :t)
perf (aliases: compute)

Built-in Commands

Piccolo introduces few built-in console commands:

• :quit (or :q) to exit the console
• :list (or :l) to list available commands
• :type (or :t) to list command parameters

Built-in commands are also created using @Command annotations.