Package org.apache.nifi.parameter

Interface ParameterProvider

All Superinterfaces:
ConfigurableComponent
All Known Implementing Classes:
AbstractParameterProvider
public interface ParameterProvider extends ConfigurableComponent
Defines a provider that is responsible for fetching from an external source Parameters with which a ParameterContext can be populated.

ParameterProviders are discovered following Java's ServiceLoader pattern. As a result, all implementations must follow these rules:

  • The implementation must implement this interface.
  • The implementation must have a file named org.apache.nifi.parameter.ParameterProvider located within the jar's META-INF/services directory. This file contains a list of fully-qualified class names of all ParameterProviders in the jar, one-per-line.
  • The implementation must support a default constructor.

All implementations of this interface must be thread-safe.

Parameter Providers may choose to annotate a method with the @OnConfigurationRestored annotation. If this is done, that method will be invoked after all properties have been set for the ParameterProvider and before its parameters are fetched.

  • Method Details

    • initialize

      void initialize(ParameterProviderInitializationContext config) throws InitializationException
      Provides the Parameter Provider with access to objects that may be of use throughout the life of the provider
      Parameters:
      config - of initialization context
      Throws:
      InitializationException - if unable to init

    • fetchParameters

      List<ParameterGroup> fetchParameters(ConfigurationContext context) throws IOException
      Fetches named groups of parameters from an external source. Any referencing Parameter Context will only receive the Parameters from a group if the Parameter Context name matches the group name (ignoring case) and the reference sensitivity matches the group sensitivity. If group name is null, all referencing Parameter Contexts will receive the Parameters in that group, regardless of their name. If more than one ProvidedParameterGroup matches a given ParameterContext, all parameters from these groups will be applied. However, if any parameters among these matching groups have the same name but different value, the framework will throw a RuntimeException
      Parameters:
      context - The ConfigurationContextfor the provider
      Returns:
      A list of fetched Parameter groups. The framework will set the sensitivity appropriately based on how the ParameterProvider is referenced in a ParameterContext.
      Throws:
      IOException - if there is an I/O problem while fetching the Parameters