Support BitSet look up out of box

[Emily-Jiang]

As a:

• Application user/user of the configuration itself
• API user (application developer)
• SPI user (container or runtime developer)
• Specification implementer

...I need to be able to:

directly inject or programmatically look BitSet in my java class without providing a converter myself.

...which enables me to:

Specify a bitset in a configsource and then I can look up from my java class
bits=10001

@Inject @ConfigProperty(name="bits") BitSet bits;

[radcortez]

Isn't this type too specific for a built in converter?

[Emily-Jiang]

Isn't this type too specific for a built in converter?

What do you mean? I think it is useful to add it to the list of built in converter.

[tomas-langer]

Why BitSet specifically? There are a lot of classes that could be supported by built-in converters such as:

• BigDecimal
• BigInteger
• all the java.time classes
• Path
• Charset
• URI
• URL
• Pattern
• UUID
• all old time classes, such as Date, Calendar, TimeZone....

And probably a lot others. I would argue there are some much more widely used than BitSet

[Emily-Jiang]

@tomas-langer most of the converters you mentioned are already supported and they are under automatic converter category. See the category details here. In more details,

If no built-in nor custom Converter exists for a requested Type T, an implicit Converter is automatically provided if the following conditions are met:

The target type T has a public static T of(String) method, or

The target type T has a public static T valueOf(String) method, or

The target type T has a public static T parse(CharSequence) method : all of java.time classes 

The target type T has a public Constructor with a String parameter : BigDecimal, BigInteger, URI, URL, Path

This leaves UUID, Charset, and Pattern.

For the old time classes, I think the java.time is more preferred and they become legacy. I suggest not to do anything for them. I will open another issue to support UUID, Charset and Pattern as built-in converters.

In the meanwhile, I'm going to close this issue of adding Bitset as built-in converter since not many people are keen with this.

[Emily-Jiang]

See #604 @tomas-langer please comment if you think more converters are to be added. I believe I have address your comments.