[TAMAYA-378] Clarify Property Key Resolution on Injection

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.3-incubating
• Fix Version/s: 0.4-incubating
• Component/s: Extensions
• Assignee: Anatole Tresch
• Reporter: Anatole Tresch
• Created: 20/Jan/19 22:47
• Updated: 14/May/19 15:03
• Resolved: 14/May/19 15:03

Description

Current Situation

Currently key resolution is very complex and leads to many different keys potentially being looked up. Given the following class:

 

package a.b.c;
public class Injected{
  @Config("myProp", "myFallbackProp")
  private String property;
}

 

Would evaluate to the following key lookup chain:

 

a.b.c.Injected.myProp
a.b.c.Injected.myFallbackProp
Injected.myProp
Injected.myFallbackProp
myProp
myFallbackProp

 

 Proposal

This is weird to the user, so the proposal is to

1. Separate the main from the fallback keys
2. Allow to define how to combine the (field)property key, with the class key.

Therefore the @Config annotation should be adapted as follows:

 

public @interface Config {

 String UNCONFIGURED_VALUE = ...;

 String key() default "";
 KeyResolution keyResolution() default KeyResolution.AUTO;
 String[] alternateKeys() default {};

 String defaultValue() default UNCONFIGURED_VALUE;
 boolean required() default true;
}

 

Herebythe enum type KeyResolution defines how the property key(s) are evaluated:

• AUTO: This is the default key resolution strateg. The targeting key is evaluated as follows:
  • The containing class does not have a @ConfigSection annotation and the field/method does not have a @Config annotation:
    the main key equals to
        Owning.class.getSimpleName() + '.' + propertyKey.
    {{This equals to }}RELATIVE_SIMPLE.
  • The containing class does not have a @ConfigArea annotation:
    the main key equals to
        propertyKey.
    This equals to ABSOLUTE

• • The containing class does have a @ConfigArea annotation:
    the main key equals to 
        _sectionAnnotation.getValue() + '.' + propertyKe_y. 
• RELATIVE_SIMPLE: The targeting key is evaluated to
  Owner.class.getSimpleName() + '.' + * propertyKey
• RELATIVE_FQN:  ** The targeting key is evaluated to 
  Owner.class.getName() + '.' + * propertyKey
• ABSOLUTE: The targeting key is evaluated to propertyKey.

Hereby this resolution policy only applies to the main property key, modelled by key(), whereas fallback keys always are considered as ABSOLUTE keys.

Example

Given the following class:

package a.b.c;
public class Injected{
  @Config(key="myProp", fallbackKeys={"myFallbackProp"})
  private String property;
}

 Would evaluate to the following key lookup chain:

Injected.myProp
myFallbackProp

 Using KeyResolution.ABSOLUTE the keys would be:

myProp
myFallbackProp

  Using KeyResolution.RELATIVE_FQN the keys would be:

a.b.c.Injected.myProp
myFallbackProp

This drastically reduces the keyset and makes the resolution more explicit and less magic IMO.

 

Issue Links

• links to: GitHub Pull Request #24
• links to: GitHub Pull Request #29
• links to: GitHub Pull Request #34