org.microbean.configuration.spi

Interface Arbiter

All Known Implementing Classes:

ComparatorBasedArbiter, ConfigurationValueSourceComparingArbiter, SystemPropertiesOutrankEnvironmentVariablesArbiter

public interface Arbiter

A resolver of ambiguous ConfigurationValues.

Author:

Laird Nelson

See Also:

arbitrate(Map, String, Collection)

Method Summary

Modifier and Type

Method and Description

ConfigurationValue

arbitrate(Map<? extends String,? extends String> requestedCoordinates, String name, Collection<? extends ConfigurationValue> ambiguousValues) Given a logical request for a configuration value, represented by the callerCoordinates and name parameter values, and a Collection of ConfigurationValue instances that represents the ambiguous response from several Configuration instances, attempts to resolve the ambiguity by returning a single ConfigurationValue instead.

Method Detail

arbitrate

ConfigurationValue arbitrate(Map<? extends String,? extends String> requestedCoordinates,
                             String name,
                             Collection<? extends ConfigurationValue> ambiguousValues)

Given a logical request for a configuration value, represented by the callerCoordinates and name parameter values, and a Collection of ConfigurationValue instances that represents the ambiguous response from several Configuration instances, attempts to resolve the ambiguity by returning a single ConfigurationValue instead.

Implementations of this method may return null.

A special case is when the supplied ambiguousValues parameter is null or empty. This means, effectively, that all consulted Configuration instances returned null from their Configuration.getValue(Map, String) methods. An Arbiter encountering this state of affairs and returning a single non-null ConfigurationValue is effectively synthesizing a default value.

Parameters:

requestedCoordinates - the (immutable) configuration coordinates in effect for the request; may be null

name - the name of the configuration value; must not be null

ambiguousValues - an immutable Collection of definitionally ambiguous ConfigurationValues that resulted from the request; may be null

Returns:

the result of arbitration, or null if the dispute cannot be arbitrated by this Arbiter

Throws:

NullPointerException - if name is null

AmbiguousConfigurationValuesException - if overall arbitration is to be cut short by this Arbiter—normally an Arbiter should simply return null