A type converter for InetSocketAddress

[sbernard31]

It could be nice to add a ITypeConverter for InetSocketAddress.

The idea is to be able to support value like :

10.0.0.1:8080
localhost:30
[2001:db8::85a3::ac1f:8001]:5555

Ideally it would be good to be able to have a way to define value for hostname or port or both meaning that you could write :

10.0.0.1
localhost
[2001:db8::85a3::ac1f:8001]
:8080

(But my guess is ITypeConverter API is not really adapted for that as it should add the default value as convert parameter)

[remkop]

I think I briefly looked at this in the early days but decided not to create a built-in converter.

We would need to decide on a separator between host and port, and although I have seen ':' used a lot, there are also many tools that require the host and port to be specified separately (space-separated). There is no unambiguous standardized format, so I thought that instead of deciding on an arbitrary one, this converter was better done with a custom implementation.

Making a custom converter is fairly straightforward, something like this:

import picocli.CommandLine;
import picocli.CommandLine.ITypeConverter;
import picocli.CommandLine.Option;
import picocli.CommandLine.TypeConversionException;

import java.net.InetSocketAddress;

public class InetSocketAddressConverterDemo {

    static class InetSocketAddressConverter implements ITypeConverter<InetSocketAddress> {
        @Override
        public InetSocketAddress convert(String value) throws Exception {
            int pos = value.lastIndexOf(':');
            if (pos < 0) {
                throw new TypeConversionException("Invalid format: must be 'host:port' but was '" + value + "'");
            }
            String adr = value.substring(0, pos);
            int port = Integer.parseInt(value.substring(pos + 1));
            return new InetSocketAddress(adr, port);
        }
    }

    @Option(names = "-a", converter = InetSocketAddressConverter.class)
    InetSocketAddress address;

    public static void main(String[] args) {
        new CommandLine(new InetSocketAddressConverterDemo()).execute("-a=invalid");
    }
}

[sbernard31]

As you said, ':' is used a lot. So even if this not really a standard, IMHO, this make sense that "the more often used syntax" get a default implementation. Nothing prevent someone else to use a custom converter if he don't want to use the default/more popular way.

Anyway this was just an idea, feel free to close the issue if you think it's not a good one 😉

Thx again for this great piece of software 🙏

[remkop]

I added a new section Handling Invalid Input for custom type converters to the user manual. During our discussion I realized the manual did not mention the TypeConversionException, and I took this opportunity to correct that. This section now shows the code for a custom InetSocketAddressConverter, to demonstrate the use of that exception.

I added a runnable example InetSocketAddressConverterDemo to the picocli-examples module.

This is not the same as getting a built-in InetSocketAddressConverter, but I hope this is still valuable. Enjoy using picocli!