Module io.inverno.mod.configuration
Package io.inverno.mod.configuration

Interface DefaultingStrategy

All Known Subinterfaces:
CompositeConfigurationStrategy.CompositeDefaultingStrategy
public interface DefaultingStrategy

A defaulting strategy is used in a DefaultableConfigurationSource to implement defaulting configuration mechanism.

A defaulting strategy derives a list of queries from an original query whose order specifies result priorities. The source shall retain the first non-empty result from that list or the empty result if no result is returned for any of the queries returned by the strategy.

Since:
1.5
Author:
Jeremy Kuhn

  • Method Details

    • noOp

      static DefaultingStrategy noOp()

      Returns a NoOp defaulting strategy.

      The NoOp defaulting strategy does not support defaulting and simply returns the original query.

      Returns:
      a NoOp defaulting strategy

    • lookup

      static DefaultingStrategy lookup()

      Returns a lookup defaulting strategy.

      A lookup defaulting strategy support defaulting by prioritizing parameters from left to right: the best matching property is the one matching the most continuous parameters from left to right.

      If we consider query key property[p1=v1,...pn=vn], it supersedes key property[p1=v1,...pn-1=vn-1] which supersedes key property[p1=v1,...pn-2=vn-2]... which supersedes key property[]. It basically tells the source to lookup by successively removing the rightmost parameter if no exact result exists for a particular query.

      As a result, an original query with n parameters results in n+1 potential queries to execute for the source. The query result is then the first non-empty result or the empty result.

      The order into which parameters are defined in the original query is then significant: property[p1=v1,p2=v2] != property[p2=v2,p1=v1].

      When listing properties, this strategy includes the parent properties which are obtained by successively removing the rightmost parameter from the original query.

      Returns:
      a lookup defaulting strategy

    • wildcard

      static DefaultingStrategy wildcard()

      Returns a wildcard defaulting strategy.

      If we consider query key property[p1=v1,...pn=vn], the most precise result is the one defining parameters [p1=v1,...pn=vn], it supersedes results that define n-1 query parameters, which supersedes results that define n-2 query parameters... which supersedes results that define no query parameters. Conflicts may arise when a source defines a property with different set of query parameters with the same cardinality (e.g. when it defines properties property[p1=v1,p2=v2] and property[p1=v1,p3=v3]). In such situation, priority is always given to parameters from left to right (therefore property[p1=v1,p2=v2] supersedes property[p1=v1,p3=v3])

      An original query with n parameters then results in 2^n potential queries to execute for the source (the sum of the k-combinations from 0 to n). The query result is the first non-empty result or the empty result.

      The order into which parameters are defined in the original query is then significant: property[p1=v1,p2=v2] != property[p2=v2,p1=v1].

      When listing properties, this strategy includes all properties that could match the query parameters.

      Returns:
      a wildcard defaulting strategy

    • getDefaultingKeys

      List<ConfigurationKey> getDefaultingKeys(ConfigurationKey queryKey)

      Derives a list of queries from the specified original query.

      The order of the returned queries must determine the result priorities. The source must consider queries in that order to determine the best matching result for the original query.

      Parameters:
      queryKey - the original query
      Returns:
      a list of configuration queries

    • getListDefaultingKeys

      List<ConfigurationKey> getListDefaultingKeys(ConfigurationKey queryKey)

      Derives a list of keys that defines the set of properties that must be retained in a list query.

      A source shall use these keys to determine whether a given property must be included in the results of a list query.

      Note that in case of a ListConfigurationQuery.executeAll() operation, the source shall only include properties with extra parameters that only match the first key so as to exclude properties inconsistent with the original query.

      Parameters:
      queryKey - the original query
      Returns:
      a list of configuration keys