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17 package org.apache.commons.configuration;
18
19 import java.lang.reflect.Method;
20 import java.util.Collection;
21 import java.util.HashMap;
22 import java.util.Iterator;
23 import java.util.Map;
24
25 import org.apache.commons.lang.SystemUtils;
26 import org.apache.tools.ant.taskdefs.Execute;
27
28 /***
29 * <p>
30 * A Configuration implementation that reads the platform specific environment
31 * variables. On pre java5 JRE it uses Ant Execute task to read the environment.
32 * (in this case ant must be present in classpath). On java >= 5 JRE it uses
33 * <code>java.lang.System#getenv()</code> and ant is not required.
34 * </p>
35 * <p>
36 * This configuration implementation is read-only. It allows read access to the
37 * defined OS environment variables, but their values cannot be changed.
38 * </p>
39 * <p>
40 * Usage of this class is easy: After an instance has been created the get
41 * methods provided by the <code>Configuration</code> interface can be used
42 * for querying environment variables, e.g.:
43 *
44 * <pre>
45 * Configuration envConfig = new EnvironmentConfiguration();
46 * System.out.println("JAVA_HOME=" + envConfig.getString("JAVA_HOME");
47 * </pre>
48 *
49 * </p>
50 *
51 * @author <a href="mailto:nicolas.deloof@gmail.com">Nicolas De Loof</a>
52 * @see org.apache.tools.ant.taskdefs.Execute#getProcEnvironment()
53 * @since 1.5
54 */
55 public class EnvironmentConfiguration extends AbstractConfiguration
56 {
57 /*** Constant for the name of the getenv() method. */
58 private static final String METHOD_NAME = "getenv";
59
60 /*** Constant for the Java version 1.5. */
61 private static final int VERSION_1_5 = 150;
62
63 /*** Stores the environment properties. */
64 private Map environment;
65
66 /***
67 * Constructor.
68 */
69 public EnvironmentConfiguration()
70 {
71 if (SystemUtils.isJavaVersionAtLeast(VERSION_1_5))
72 {
73 extractProperties15();
74 }
75 else
76 {
77 extractProperties14();
78 }
79 }
80
81 /***
82 * Adds a property to this configuration. Because this configuration is
83 * read-only, this operation is not allowed and will cause an exception.
84 *
85 * @param key the key of the property to be added
86 * @param value the property value
87 */
88 protected void addPropertyDirect(String key, Object value)
89 {
90 throw new UnsupportedOperationException("Configuration is read-only!");
91 }
92
93 /***
94 * {@inheritDoc}
95 *
96 * @see org.apache.commons.configuration.AbstractConfiguration#containsKey(java.lang.String)
97 */
98 public boolean containsKey(String key)
99 {
100 return environment.containsKey(key);
101 }
102
103 /***
104 * {@inheritDoc}
105 *
106 * @see org.apache.commons.configuration.AbstractConfiguration#getKeys()
107 */
108 public Iterator getKeys()
109 {
110 return environment.keySet().iterator();
111 }
112
113 /***
114 * {@inheritDoc}
115 *
116 * @see org.apache.commons.configuration.AbstractConfiguration#getProperty(java.lang.String)
117 */
118 public Object getProperty(String key)
119 {
120 return environment.get(key);
121 }
122
123 /***
124 * {@inheritDoc}
125 *
126 * @see org.apache.commons.configuration.AbstractConfiguration#isEmpty()
127 */
128 public boolean isEmpty()
129 {
130 return environment.isEmpty();
131 }
132
133 /***
134 * Removes a property from this configuration. Because this configuration is
135 * read-only, this operation is not allowed and will cause an exception.
136 *
137 * @param key the key of the property to be removed
138 */
139 public void clearProperty(String key)
140 {
141 throw new UnsupportedOperationException("Configuration is read-only!");
142 }
143
144 /***
145 * Removes all properties from this configuration. Because this
146 * configuration is read-only, this operation is not allowed and will cause
147 * an exception.
148 */
149 public void clear()
150 {
151 throw new UnsupportedOperationException("Configuration is read-only!");
152 }
153
154 /***
155 * Extracts environment properties on a JRE < 1.5. This implementation
156 * uses ant for this purpose.
157 */
158 void extractProperties14()
159 {
160 extractPropertiesFromCollection(Execute.getProcEnvironment());
161 }
162
163 /***
164 * An internally used method for processing a collection with environment
165 * entries. The collection must contain strings like
166 * <code>property=value</code>. Such a collection is returned by ant.
167 *
168 * @param env the collection with the properties
169 */
170 void extractPropertiesFromCollection(Collection env)
171 {
172 environment = new HashMap();
173 for (Iterator it = env.iterator(); it.hasNext();)
174 {
175 String entry = (String) it.next();
176 int pos = entry.indexOf('=');
177 if (pos == -1)
178 {
179 getLogger().warn("Ignoring: " + entry);
180 }
181 else
182 {
183 environment.put(entry.substring(0, pos), entry
184 .substring(pos + 1));
185 }
186 }
187 }
188
189 /***
190 * Extracts environment properties on a JR >= 1.5. From this Java version
191 * on, there is an official way of doing this. However because the code
192 * should compile on lower Java versions, too, we have to invoke the method
193 * using reflection.
194 */
195 void extractProperties15()
196 {
197 try
198 {
199 Method method = System.class.getMethod(METHOD_NAME, null);
200 environment = (Map) method.invoke(null, null);
201 }
202 catch (Exception ex)
203 {
204
205 throw new ConfigurationRuntimeException(
206 "Error when accessing environment properties", ex);
207 }
208 }
209 }