[jboss-jira] [JBoss JIRA] Commented: (JGRP-1068) Add programmer assigned default processing to @Property annotations

[Richard Achmatowicz (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12488245#action_12488245 ] 

Richard Achmatowicz commented on JGRP-1068:
-------------------------------------------

This reflects what I understood during our discussion this morning.
One small issue concerning how we get the defaults. You are suggesting to add attributes defaultIPv4 and defaultIPv6 to allow specifying IP version specific defaults for properties which represent InetAddress (or related) values. The annotation @Property is used for all user specified properties, whether they be int, float or  List<IpAddress>. But defaultIPv4 and defaultIPv6 don't generally make sense for int or float.
I'm just wondering whether we could (or should?) define @Property like this:

public @interface Property {
   String name() default "";
   String description() default "";
   String deprecatedMessage() default "";
   Class<?> converter() default PropertyConverters.Default.class;      String dependsUpon() default "";
   Striing default() default "";
   Striing defaultIPv4() default "";
   Striing defaultIPv6() default "";
}

and have a default mechanism for fields other than InetAddress values (e.g. some structure which requires a converter to generate its initial value from  a string but which is not related to InetAddresses). So the scheme works exactly as above, except that every field can now have a default String value assigned:

@Property(dependsUpon="mcast_port", defaultIPv4="224.5.6.7", defaultIPv6="::FF88",converter=IpAddressConverter.class)
private IpAddress mcast_addr;
@Property(default="1234",converter=Default.class)
private int mcast_port;

So if the user does not specify a mcast_port value (ie.. props.get("mcast_port") == null), then the default value is taken from the Property.default() call.
So any variable can have a default assigned using this mechanism: use default() for non-InetAddress variables, and  defaultIPv4()/default(IPv6()  for InetAddress related variables.

mcast_port maybe isn't a good example, because it may need to be generated during init() based on which ports are available, but there may be other data structures which require generation of a default value by a converter (e.g. some kind of List  or Map) which can't conveniently be defined statically. 

> Add programmer assigned default processing to @Property annotations
> -------------------------------------------------------------------
>
>                 Key: JGRP-1068
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1068
>             Project: JGroups
>          Issue Type: Feature Request
>    Affects Versions: 2.8
>            Reporter: Richard Achmatowicz
>            Assignee: Richard Achmatowicz
>            Priority: Minor
>             Fix For: 2.8
>
>
> There is a need to handle in a systematic way the assignment of programmer assigned defaults to properties in JGroups. THis issue concerns incorporating the assignment of progranmmer assigned defaults using the existing @Property mechanism.
> The following comments explain the issue.
>  

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