1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.configuration; 19 20 import java.util.HashMap; 21 22 /** 23 * <p>A Configuration implementation that reads the platform specific 24 * environment variables using the map returned by {@link System#getenv()}.</p> 25 * 26 * <p>This configuration implementation is read-only. It allows read access to the 27 * defined OS environment variables, but their values cannot be changed. Any 28 * attempts to add or remove a property will throw an 29 * {@link UnsupportedOperationException}</p> 30 * 31 * <p>Usage of this class is easy: After an instance has been created the get 32 * methods provided by the {@code Configuration} interface can be used 33 * for querying environment variables, e.g.:</p> 34 * 35 * <pre> 36 * Configuration envConfig = new EnvironmentConfiguration(); 37 * System.out.println("JAVA_HOME=" + envConfig.getString("JAVA_HOME"); 38 * </pre> 39 * 40 * @author <a href="mailto:nicolas.deloof@gmail.com">Nicolas De Loof</a> 41 * @version $Id: EnvironmentConfiguration.java 1210171 2011-12-04 18:32:07Z oheger $ 42 * @since 1.5 43 */ 44 public class EnvironmentConfiguration extends MapConfiguration 45 { 46 /** 47 * Create a Configuration based on the environment variables. 48 * 49 * @see System#getenv() 50 */ 51 public EnvironmentConfiguration() 52 { 53 super(new HashMap<String, Object>(System.getenv())); 54 } 55 56 /** 57 * Adds a property to this configuration. Because this configuration is 58 * read-only, this operation is not allowed and will cause an exception. 59 * 60 * @param key the key of the property to be added 61 * @param value the property value 62 */ 63 @Override 64 protected void addPropertyDirect(String key, Object value) 65 { 66 throw new UnsupportedOperationException("EnvironmentConfiguration is read-only!"); 67 } 68 69 /** 70 * Removes a property from this configuration. Because this configuration is 71 * read-only, this operation is not allowed and will cause an exception. 72 * 73 * @param key the key of the property to be removed 74 */ 75 @Override 76 public void clearProperty(String key) 77 { 78 throw new UnsupportedOperationException("EnvironmentConfiguration is read-only!"); 79 } 80 81 /** 82 * Removes all properties from this configuration. Because this 83 * configuration is read-only, this operation is not allowed and will cause 84 * an exception. 85 */ 86 @Override 87 public void clear() 88 { 89 throw new UnsupportedOperationException("EnvironmentConfiguration is read-only!"); 90 } 91 }