Module io.helidon.config
Package io.helidon.config

Class MetaConfig

java.lang.Object
io.helidon.config.MetaConfig
@Provider public final class MetaConfig extends Object
Meta configuration.

Configuration allows configuring itself using meta configuration. Config looks for meta-config.* files in the current directory and on the classpath, where the * is one of the supported media type suffixes (such as yaml when helidon-config-yaml module is on the classpath).

Meta configuration can define which config sources to load, including possible retry policy, polling strategy and change watchers.

Example of a YAML meta configuration file: 

 sources:
   - type: "environment-variables"
   - type: "system-properties"
   - type: "file"
     properties:
       path: "conf/dev.yaml"
       optional: true
   - type: "file"
     properties:
       path: "conf/config.yaml"
       optional: true
   - type: "classpath"
     properties:
       resource: "default.yaml"
This configuration would load the following config sources (in the order specified):
  • Environment variables config source
  • System properties config source
  • File config source from file conf/dev.yaml that is optional
  • File config source from file conf/config.yaml that is optional
  • Classpath resource config source for resource default.yaml that is mandatory

  • Method Details

    • config

      public static Config config()
      Create configuration from meta configuration (files or classpath resources), or create a default config instance if meta configuration is not present.
      Returns:
      a config instance

    • config

      public static Config config(Config metaConfig)
      Create configuration from provided meta configuration.
      Parameters:
      metaConfig - meta configuration
      Returns:
      a new config instance built from meta configuration

    • metaConfig

      public static Optional<Config> metaConfig()
      Find meta configuration (files or classpath resources) and create a meta configuration instance from it.
      Returns:
      meta configuration if present, or empty

    • pollingStrategy

      public static PollingStrategy pollingStrategy(Config metaConfig)
      Load a polling strategy based on its meta configuration.
      Parameters:
      metaConfig - meta configuration of a polling strategy
      Returns:
      a polling strategy instance

    • changeWatcher

      public static ChangeWatcher<?> changeWatcher(Config metaConfig)
      Load a change watcher based on its meta configuration.
      Parameters:
      metaConfig - meta configuration of a change watcher
      Returns:
      a change watcher instance

    • retryPolicy

      public static RetryPolicy retryPolicy(Config metaConfig)
      Load a retry policy based on its meta configuration.
      Parameters:
      metaConfig - meta configuration of retry policy
      Returns:
      retry policy instance

    • configSource

      public static List<ConfigSource> configSource(Config sourceMetaConfig)
      Load a config source (or config sources) based on its meta configuration. The metaConfig must contain a key type that defines the type of the source to be found via providers, and a key properties with configuration of the config sources
      Parameters:
      sourceMetaConfig - meta configuration of a config source
      Returns:
      config source instance
      See Also:

    • metaConfiguration

      public Config metaConfiguration()
      Meta configuration if provided, or empty config if not.
      Returns:
      meta configuration