Descriptor annotation

[wsargent]

One of the useful things about descriptors is they can specify default values, min and max value and useful metadata on attributes:

• https://docs.oracle.com/javase/8/docs/technotes/guides/jmx/tutorial/essential.html#wp1055639
• https://docs.oracle.com/javase/8/docs/api/javax/management/Descriptor.html
• https://docs.oracle.com/javase/8/docs/technotes/guides/jmx/JMX_1_4_specification.pdf section 4.4

It'd be nice to have an annotation that could represent this next to an attribute. There is an immutable descriptor used for sort, but not the general purpose descriptor values.

https://github.com/uklimaschewski/JMXWrapper/blob/master/src/com/udojava/jmx/wrapper/JMXBeanWrapper.java#L567

For example, using the DescriptorKey meta-annotation someone may define a Units("inches") annotation

@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Units {
    @DescriptorKey("units")
    String value();
}

And JMXWrapper could then pick up the annotation on attribute and add it to the descriptor at runtime.