http://commons.apache.org/configuration/: Tools to assist in the reading of configuration/preferences files in various formats. (The Apache Software Foundation)
  • Konstantin Shaposhnikov (scand.com)
  • Jamie M. Guillemette (TD Bank)
  • Jorge Ferrer ()
  • Gabriele Garuglieri (Infoblu S.p.A)
  • Nicolas De Loof (Cap Gemini)
  • Daniel Rall (CollabNet, Inc.)
  • Jason van Zyl (Zenplex)
  • Martin Poeschl (tucana.at)
  • dIon Gillard (Multitask Consulting)
  • Henning P. Schmiedehausen
  • Eric Pugh (upstate.com)
  • Brian E. Dunbar (dunbarconsulting.org)
  • Emmanuel Bourg (Ariane Software)
  • Oliver Heger (Agfa HealthCare)
  • Jörg Schaible
  • Ralph Goers (Intuit) 
/*
 * 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.configuration.interpol;

import org.apache.commons.configuration.EnvironmentConfiguration;
import org.apache.commons.lang.text.StrLookup;



A specialized lookup implementation that allows access to environment
variables.



 This implementation relies on EnvironmentConfiguration to resolve environment variables. It can be used for referencing environment variables in configuration files in an easy way, for instance: 
java.home = ${env:JAVA_HOME}





 EnvironmentLookup is one of the standard lookups that is registered per default for each configuration. 


Author:Commons
        Configuration team
Since:1.7
Version:$Id: EnvironmentLookup.java 1210620 2011-12-05 20:57:31Z oheger $
/**
 * <p>
 * A specialized lookup implementation that allows access to environment
 * variables.
 * </p>
 * <p>
 * This implementation relies on {@link EnvironmentConfiguration} to resolve
 * environment variables. It can be used for referencing environment variables
 * in configuration files in an easy way, for instance:
 *
 * <pre>
 * java.home = ${env:JAVA_HOME}
 * </pre>
 *
 * </p>
 * <p>
 * {@code EnvironmentLookup} is one of the standard lookups that is
 * registered per default for each configuration.
 * </p>
 *
 * @author <a
 *         href="http://commons.apache.org/configuration/team-list.html">Commons
 *         Configuration team</a>
 * @since 1.7
 * @version $Id: EnvironmentLookup.java 1210620 2011-12-05 20:57:31Z oheger $
 */
public class EnvironmentLookup extends StrLookup
{
    
Stores the underlying EnvironmentConfiguration. 
/** Stores the underlying {@code EnvironmentConfiguration}. */
    private final EnvironmentConfiguration environmentConfig = new EnvironmentConfiguration();

    
Performs a lookup for the specified variable. This implementation directly delegates to a EnvironmentConfiguration. 
Params:
  • key – the key to lookup
Returns:the value of this key or null if it cannot be resolved
/**
     * Performs a lookup for the specified variable. This implementation
     * directly delegates to a {@code EnvironmentConfiguration}.
     *
     * @param key the key to lookup
     * @return the value of this key or <b>null</b> if it cannot be resolved
     */
    @Override
    public String lookup(String key)
    {
        return environmentConfig.getString(key);
    }
}