/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.configuration2;

import org.apache.commons.configuration2.interpol.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/**
 * <p>
 * A specialized implementation of the {@code Lookup} interface which uses a
 * {@code Configuration} object to resolve variables.
 * </p>
 * <p>
 * This class is passed an {@link ImmutableConfiguration} object at construction
 * time. In its implementation of the {@code lookup()} method it simply queries
 * this configuration for the passed in variable name. So the keys passed to
 * {@code lookup()} are mapped directly to configuration properties.
 * </p>
 *
 * @since 2.0
 */
public class ConfigurationLookup implements Lookup
{
    
The configuration to which lookups are delegated. /** The configuration to which lookups are delegated. */
    private final ImmutableConfiguration configuration;

    
Creates a new instance of ConfigurationLookup and sets the associated ImmutableConfiguration. 
Params:
config – the configuration to use for lookups (must not be
       null)
Throws:
IllegalArgumentException – if the configuration is null/**
     * Creates a new instance of {@code ConfigurationLookup} and sets the
     * associated {@code ImmutableConfiguration}.
     *
     * @param config the configuration to use for lookups (must not be
     *        <b>null</b>)
     * @throws IllegalArgumentException if the configuration is <b>null</b>
     */
    public ConfigurationLookup(final ImmutableConfiguration config)
    {
        if (config == null)
        {
            throw new IllegalArgumentException(
                    "Configuration must not be null!");
        }
        configuration = config;
    }

    
Returns the ImmutableConfiguration used by this object. 
Returns:
the associated ImmutableConfiguration/**
     * Returns the {@code ImmutableConfiguration} used by this object.
     *
     * @return the associated {@code ImmutableConfiguration}
     */
    public ImmutableConfiguration getConfiguration()
    {
        return configuration;
    }

    
{@inheritDoc} This implementation calls getProperty() on the associated configuration. The return value is directly returned. Note that this may be a complex object, e.g. a collection or an array. /**
     * {@inheritDoc} This implementation calls {@code getProperty()} on the
     * associated configuration. The return value is directly returned. Note
     * that this may be a complex object, e.g. a collection or an array.
     */
    @Override
    public Object lookup(final String variable)
    {
        return getConfiguration().getProperty(variable);
    }
}