001//////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code for adherence to a set of rules. 003// Copyright (C) 2001-2014 Oliver Burn 004// 005// This library is free software; you can redistribute it and/or 006// modify it under the terms of the GNU Lesser General Public 007// License as published by the Free Software Foundation; either 008// version 2.1 of the License, or (at your option) any later version. 009// 010// This library is distributed in the hope that it will be useful, 011// but WITHOUT ANY WARRANTY; without even the implied warranty of 012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 013// Lesser General Public License for more details. 014// 015// You should have received a copy of the GNU Lesser General Public 016// License along with this library; if not, write to the Free Software 017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018//////////////////////////////////////////////////////////////////////////////// 019package com.puppycrawl.tools.checkstyle; 020 021import java.util.Properties; 022 023/** 024 * Resolves external properties from an 025 * underlying <code>Properties</code> object. 026 * 027 * @author lkuehne 028 */ 029public final class PropertiesExpander 030 implements PropertyResolver 031{ 032 /** the underlying Properties object. */ 033 private final Properties properties; 034 035 /** 036 * Creates a new PropertiesExpander. 037 * @param properties the underlying properties to use for 038 * property resolution. 039 * @throws IllegalArgumentException indicates null was passed 040 */ 041 public PropertiesExpander(Properties properties) 042 { 043 if (properties == null) { 044 throw new IllegalArgumentException("cannot pass null"); 045 } 046 this.properties = properties; 047 } 048 049 /** {@inheritDoc} */ 050 @Override 051 public String resolve(String propertyName) 052 { 053 return properties.getProperty(propertyName); 054 } 055}