[jira] [Created] (DELTASPIKE-1241) [Config] fallback chain logic

["Mark Struberg (JIRA)" <ji...@apache.org>]

Mark Struberg created DELTASPIKE-1241:
-----------------------------------------

             Summary: [Config] fallback chain logic
                 Key: DELTASPIKE-1241
                 URL: https://issues.apache.org/jira/browse/DELTASPIKE-1241
             Project: DeltaSpike
          Issue Type: New Feature
          Components: Configuration
    Affects Versions: 1.7.2
            Reporter: Mark Struberg
            Assignee: Mark Struberg
             Fix For: 1.8.0


We got the request to add handling similar to ConfigResolver#getProjectStageAwarePropertyValue and ConfigResolver#getPropertyAwarePropertyValue but in a more generic way.

Something I've been experimenting with since a long time was to introduce a more generic logic based on different lookup paths with themselves represent a postfix. 

The idea is to extend the TypedResolver with a method

{code}
TypedResolver#withLookupPath(String... lookupPaths)
{code} 
where each lookupPath String could either be a hardcoded value (e.g. evaluated upfront) or a variable "${somevariable}" which will be evaluted on the fly. 

ConfigResolver.getPropertyAwarePropertyValue("dbvendor") could e.g. also be written as 

{code}
TypedResolver<String> ds = 
    ConfigResolver.resolve("myprj.datasource")
       .withLookupPath("${dbvendor}", "${deltaspike.projectstage}");
ds.get();
{code}

Assuming we are in the ProjectStage UnitTest this would result in the following lookup paths:

     * datasource.mysql.UnitTest
     * datasource.mysql
     * datasource.UnitTest
     * datasource

The lookupChain is kind of a binary field with all flags set to 1 (in the sample this would be: 11) and then decremented for each lookup (11, 10, 01, 00). Where 1 means to lookup with the specific postfix and 0 without.



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