org.apache.tamaya.spi

Interface PropertyValueCombinationPolicy

public interface PropertyValueCombinationPolicy

Policy that determines how the final value of a configuration entry is evaluated. An instances of this interface can be registered to get control how multiple PropertySources are combined. This is useful in cases where the default overriding policy as implemented in DEFAULT_OVERRIDING_COLLECTOR is not matching the need of the current application, e.g. then entries containing multiple values should be combined to new values instead of overridden.

Field Summary

Fields

Modifier and Type	Field and Description
static PropertyValueCombinationPolicy	DEFAULT_OVERRIDING_COLLECTOR Default overriding collector, where each existing entry (current is overridden by a subsequent non-null entry evaluated by propertySource.get(key).

Method Summary

Methods

Modifier and Type	Method and Description
String	collect(String currentValue, String key, PropertySource propertySource) Method that is called for each value evaluated by a PropertySource for the given key.

Field Detail

DEFAULT_OVERRIDING_COLLECTOR

static final PropertyValueCombinationPolicy DEFAULT_OVERRIDING_COLLECTOR

Default overriding collector, where each existing entry (current is overridden by a subsequent non-null entry evaluated by propertySource.get(key).

Method Detail

collect

String collect(String currentValue,
             String key,
             PropertySource propertySource)

Method that is called for each value evaluated by a PropertySource for the given key. This method is called either when a single key is accessed, e.g. by calling org.apache.tamaya.Configuration.getXXX, but also when the full configuration property map is accessed by calling Configuration.getProperties().

Parameters:

currentValue - the current value, including null. The collector should either combine the existing value with value from currentValue or replace the value in currentValue with valueRead, hereby returning the result to be used as new currentValue.

key - The current key to be evaluated.

propertySource - The PropertySource that may return an value for the given key. The PropertySource given may be evaluated for additional meta-data, how the given values are to be combined. Note that the value returned by a PropertySource can be null. In that case currentValue should be returned in almost all cases.

Returns:

the value to be used for future evaluation.