Package org.apache.commons.configuration2

# Class ConfigurationLookup

java.lang.Object
org.apache.commons.configuration2.ConfigurationLookup

All Implemented Interfaces:
  `Lookup`

public class ConfigurationLookup extends Object implements Lookup

A specialized implementation of the `Lookup` interface which uses a `Configuration` object to resolve variables.

This class is passed an `ImmutableConfiguration` object at construction time. In its implementation of the `lookup()` method it simply queries this configuration for the passed in variable name. So the keys passed to `lookup()` are mapped directly to configuration properties.

Since:
  2.0

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `ConfigurationLookup(ImmutableConfiguration config)`
  Creates a new instance of `ConfigurationLookup` and sets the associated `ImmutableConfiguration`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `ImmutableConfiguration`
  `getConfiguration()`
  Gets the `ImmutableConfiguration` used by this object.
  `Object`
  `lookup(String variable)`
  Looks up the value of the specified variable.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### ConfigurationLookup

    public ConfigurationLookup(ImmutableConfiguration config)
    Creates a new instance of `ConfigurationLookup` and sets the associated `ImmutableConfiguration`.
    Parameters:
      `config` - the configuration to use for lookups (must not be null)
    Throws:
      `IllegalArgumentException` - if the configuration is null

- ## Method Details

  - ### getConfiguration

    public ImmutableConfiguration getConfiguration()
    Gets the `ImmutableConfiguration` used by this object.
    Returns:
      the associated `ImmutableConfiguration`

  - ### lookup

    public Object lookup(String variable)
    Looks up the value of the specified variable. This method is called by `ConfigurationInterpolator` with the variable name extracted from the expression to interpolate (i.e. the prefix name has already been removed). A concrete implementation has to return the value of this variable or null if the variable name is unknown. This implementation calls `getProperty()` on the associated configuration. The return value is directly returned. Note that this may be a complex object, for example a collection or an array.
    Specified by:
      `lookup` in interface `Lookup`
    Parameters:
      `variable` - the name of the variable to be resolved
    Returns:
      the value of this variable or null