liquibase.configuration.ConfigurationValueProvider
Overview
liquibase.configuration.ConfigurationValueProvider implementations define where and how to look up configuration settings exposed through the liquibase.configuration.LiquibaseConfiguration facade.
The configuration settings looked up through these providers are used by both global and command-specific settings.
ConfigurationValueProvider Precedence
When a specific configuration key is looked for, Liquibase will check for the value in all registered ConfigurationValueProviders.
Each ConfigurationValueProvider has a getPrecedence() method which controls which value "wins" if it is configured in multiple places.
The standard provider precedence is:
- 400
liquibase.configuration.core.ScopeValueProvider - 250 Integration-specific providers such as "CLI Arguments"
- 200
liquibase.configuration.core.SystemPropertyValueProvider - 150
liquibase.configuration.core.EnvironmentValueProvider - 50
liquibase.configuration.core.DefaultsFileValueProvider
API Highlights
Auto-Registration
If the value provider can be dynamically discovered, it must have a no-arg constructor and be registered in META-INF/services/liquibase.configuration.ConfigurationValueProvider.
If it will be created programmatically by an integration, it can accept required fields in the constructor and should NOT be registered.
getPrecedence()
Returns where the value provider falls in the hierarchy of locations to check for values.
getProvidedValue()
Looks up the given configuration key in the source data.
The key(s) passed will be the canonical/standard key for the property (such as liquibase.shouldRun) plus any aliases that may apply.
It is up to implementations to provide any "smoothing" to handle differences in case, word separators, etc. that may be expected from how the data is stored
and to check for all passed keys. If multiple passed keys match, return the value from the first key in the array.
If using AbstractMapConfigurationValueProvider, override getMap() and keyMatches() instead of this method.
getMap() / keyMatches()
If using AbstractMapConfigurationValueProvider, getMap() and keyMatches() replace needing to implement getProvidedValue().
The getMap() method is called when a value is first requested from the instance.
The keyMatches() method is for defining the "smoothing" logic that handles differences in case, word separators, etc. that may be expected from how the data is stored.
For example, EnvironmentVariableValueProvider checks case-insensitively and replaces .s with _s.
If you are not extending AbstractMapConfigurationValueProvider these methods will not exist, so you will have to implement getProvidedValue() instead.
API Details
The complete javadocs for liquibase.configuration.ConfigurationValueProvider is available at https://javadocs.liquibase.com
Extension Guides
The following guides provide relevant examples: