001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.configuration2; 018 019import org.apache.commons.configuration2.interpol.Lookup; 020 021/** 022 * <p> 023 * A specialized implementation of the {@code Lookup} interface which uses a 024 * {@code Configuration} object to resolve variables. 025 * </p> 026 * <p> 027 * This class is passed an {@link ImmutableConfiguration} object at construction 028 * time. In its implementation of the {@code lookup()} method it simply queries 029 * this configuration for the passed in variable name. So the keys passed to 030 * {@code lookup()} are mapped directly to configuration properties. 031 * </p> 032 * 033 * @since 2.0 034 */ 035public class ConfigurationLookup implements Lookup 036{ 037 /** The configuration to which lookups are delegated. */ 038 private final ImmutableConfiguration configuration; 039 040 /** 041 * Creates a new instance of {@code ConfigurationLookup} and sets the 042 * associated {@code ImmutableConfiguration}. 043 * 044 * @param config the configuration to use for lookups (must not be 045 * <b>null</b>) 046 * @throws IllegalArgumentException if the configuration is <b>null</b> 047 */ 048 public ConfigurationLookup(final ImmutableConfiguration config) 049 { 050 if (config == null) 051 { 052 throw new IllegalArgumentException( 053 "Configuration must not be null!"); 054 } 055 configuration = config; 056 } 057 058 /** 059 * Returns the {@code ImmutableConfiguration} used by this object. 060 * 061 * @return the associated {@code ImmutableConfiguration} 062 */ 063 public ImmutableConfiguration getConfiguration() 064 { 065 return configuration; 066 } 067 068 /** 069 * {@inheritDoc} This implementation calls {@code getProperty()} on the 070 * associated configuration. The return value is directly returned. Note 071 * that this may be a complex object, e.g. a collection or an array. 072 */ 073 @Override 074 public Object lookup(final String variable) 075 { 076 return getConfiguration().getProperty(variable); 077 } 078}