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From aledsage <...@git.apache.org>
Subject [GitHub] brooklyn-server pull request #462: Inherit config default values
Date Fri, 10 Feb 2017 12:35:45 GMT
Github user aledsage commented on a diff in the pull request:

    https://github.com/apache/brooklyn-server/pull/462#discussion_r100509157
  
    --- Diff: core/src/main/java/org/apache/brooklyn/core/config/BasicConfigInheritance.java
---
    @@ -28,51 +32,188 @@
     import org.apache.brooklyn.config.ConfigKey;
     import org.apache.brooklyn.config.ConfigValueAtContainer;
     import org.apache.brooklyn.util.collections.CollectionMerger;
    +import org.apache.brooklyn.util.exceptions.Exceptions;
     import org.apache.brooklyn.util.exceptions.ReferenceWithError;
     import org.apache.brooklyn.util.guava.Maybe;
    +import org.apache.brooklyn.util.text.Strings;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
     
    +@SuppressWarnings("serial")
     public class BasicConfigInheritance implements ConfigInheritance {
     
    +    private static final Logger log = LoggerFactory.getLogger(BasicConfigInheritance.class);
    +    
         private static final long serialVersionUID = -5916548049057961051L;
     
         public static final String CONFLICT_RESOLUTION_STRATEGY_DEEP_MERGE = "deep_merge";
         public static final String CONFLICT_RESOLUTION_STRATEGY_OVERWRITE = "overwrite";
         
    +    public static abstract class DelegatingConfigInheritance implements ConfigInheritance
{
    +        protected abstract ConfigInheritance getDelegate();
    +        
    +        @Override @Deprecated public InheritanceMode isInherited(ConfigKey<?> key,
Object from, Object to) {
    +            return getDelegate().isInherited(key, from, to);
    +        }
    +        @Override public <TContainer, TValue> boolean isReinheritable(ConfigValueAtContainer<TContainer,
TValue> parent, ConfigInheritanceContext context) {
    +            return getDelegate().isReinheritable(parent, context);
    +        }
    +        @Override public <TContainer, TValue> boolean considerParent(ConfigValueAtContainer<TContainer,
TValue> local, ConfigValueAtContainer<TContainer, TValue> parent, ConfigInheritanceContext
context) {
    +            return getDelegate().considerParent(local, parent, context);
    +        }
    +        @Override
    +        public <TContainer, TValue> ReferenceWithError<ConfigValueAtContainer<TContainer,
TValue>> resolveWithParent(ConfigValueAtContainer<TContainer, TValue> local, ConfigValueAtContainer<TContainer,
TValue> resolvedParent, ConfigInheritanceContext context) {
    +            return getDelegate().resolveWithParent(local, resolvedParent, context);
    +        }
    +        @Override
    +        public boolean equals(Object obj) {
    +            return super.equals(obj) || getDelegate().equals(obj);
    +        }
    +        
    +        // standard deserialization method
    +        protected ConfigInheritance readResolve() {
    +            return returnEquivalentConstant(this);
    +        }
    +    }
    +
    +    private static ConfigInheritance returnEquivalentConstant(ConfigInheritance candidate)
{
    +        for (ConfigInheritance knownMode: Arrays.asList(
    +                NOT_REINHERITED, NOT_REINHERITED_ELSE_DEEP_MERGE, NEVER_INHERITED, OVERWRITE,
BasicConfigInheritance.DEEP_MERGE)) {
    +            if (candidate.equals(knownMode)) return knownMode;
    +        }
    +        if (candidate.equals(new BasicConfigInheritance(false, CONFLICT_RESOLUTION_STRATEGY_OVERWRITE,
true, true))) {
    +            // ignore the ancestor flag for this mode
    +            return NEVER_INHERITED;
    +        }
    +        return candidate;
    +    }
    +    
    +    /*
    +     * use of delegate is so that stateless classes can be defined to make the serialization
nice,
    +     * both the name and hiding the implementation detail (also making it easier for
that detail to change);
    +     * with aliased type names the field names here could even be aliases for the type
names.
    +     * (we could alternatively have an "alias-for-final-instance" mode in serialization,
    +     * to optimize where we know that a java instance is final.)   
    +     */
    +    
    +    private static class NotReinherited extends DelegatingConfigInheritance {
    +        final static BasicConfigInheritance DELEGATE = new BasicConfigInheritance(false,
CONFLICT_RESOLUTION_STRATEGY_OVERWRITE, false, true); 
    +        @Override protected ConfigInheritance getDelegate() { return DELEGATE; }
    +    }
         /** Indicates that a config key value should not be passed down from a container
where it is defined.
          * Unlike {@link #NEVER_INHERITED} these values can be passed down if set as anonymous
keys at a container
          * (ie the container does not expect it) to a container which does expect it, but
it will not be passed down further. 
          * If the inheritor also defines a value the parent's value is ignored irrespective

          * (as in {@link #OVERWRITE}; see {@link #NOT_REINHERITED_ELSE_DEEP_MERGE} if merging
is desired). */
    -    public static BasicConfigInheritance NOT_REINHERITED = new BasicConfigInheritance(false,CONFLICT_RESOLUTION_STRATEGY_OVERWRITE,false);
    +    public static ConfigInheritance NOT_REINHERITED = new NotReinherited();
    --- End diff --
    
    Very interested in @neykov's suggested alternative here, for a "less mind-bending, delegate-free
implementation". Not sure I fully understand the implications (especially relating to the
comment above about "use of delegate is so that stateless classes can be defined to make the
serialization nice..."). I've not spent long enough bending my mind during this review :-)


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