/*
* 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;
/**
* <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</code> 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 833896 2009-11-08 17:38:19Z oheger $
*/
public class EnvironmentLookup extends StrLookup
{
/** Stores the underlying <code>EnvironmentConfiguration</code>. */
private final EnvironmentConfiguration environmentConfig = new EnvironmentConfiguration();
/**
* Performs a lookup for the specified variable. This implementation
* directly delegates to a <code>EnvironmentConfiguration</code>.
*
* @param key the key to lookup
* @return the value of this key or <b>null</b> if it cannot be resolved
*/
public String lookup(String key)
{
return environmentConfig.getString(key);
}
}
|