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Tools to assist in the reading of configuration/preferences files in
various formats
/*
* 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;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import org.apache.commons.lang.SystemUtils;
import org.apache.tools.ant.taskdefs.Execute;
/**
*
* A Configuration implementation that reads the platform specific environment
* variables. On pre java5 JRE it uses Ant Execute task to read the environment.
* (in this case ant must be present in classpath). On java >= 5 JRE it uses
* java.lang.System#getenv() and ant is not required.
*
*
* This configuration implementation is read-only. It allows read access to the
* defined OS environment variables, but their values cannot be changed.
*
*
* Usage of this class is easy: After an instance has been created the get
* methods provided by the Configuration interface can be used
* for querying environment variables, e.g.:
*
*
* Configuration envConfig = new EnvironmentConfiguration();
* System.out.println("JAVA_HOME=" + envConfig.getString("JAVA_HOME");
*
*
*
*
* @author Nicolas De Loof
* @see org.apache.tools.ant.taskdefs.Execute#getProcEnvironment()
* @since 1.5
*/
public class EnvironmentConfiguration extends AbstractConfiguration
{
/** Constant for the name of the getenv() method. */
private static final String METHOD_NAME = "getenv";
/** Constant for the Java version 1.5. */
private static final int VERSION_1_5 = 150;
/** Stores the environment properties. */
private Map environment;
/**
* Constructor.
*/
public EnvironmentConfiguration()
{
if (SystemUtils.isJavaVersionAtLeast(VERSION_1_5))
{
extractProperties15();
}
else
{
extractProperties14();
}
}
/**
* Adds a property to this configuration. Because this configuration is
* read-only, this operation is not allowed and will cause an exception.
*
* @param key the key of the property to be added
* @param value the property value
*/
protected void addPropertyDirect(String key, Object value)
{
throw new UnsupportedOperationException("Configuration is read-only!");
}
/**
* {@inheritDoc}
*
* @see org.apache.commons.configuration.AbstractConfiguration#containsKey(java.lang.String)
*/
public boolean containsKey(String key)
{
return environment.containsKey(key);
}
/**
* {@inheritDoc}
*
* @see org.apache.commons.configuration.AbstractConfiguration#getKeys()
*/
public Iterator getKeys()
{
return environment.keySet().iterator();
}
/**
* {@inheritDoc}
*
* @see org.apache.commons.configuration.AbstractConfiguration#getProperty(java.lang.String)
*/
public Object getProperty(String key)
{
return environment.get(key);
}
/**
* {@inheritDoc}
*
* @see org.apache.commons.configuration.AbstractConfiguration#isEmpty()
*/
public boolean isEmpty()
{
return environment.isEmpty();
}
/**
* Removes a property from this configuration. Because this configuration is
* read-only, this operation is not allowed and will cause an exception.
*
* @param key the key of the property to be removed
*/
public void clearProperty(String key)
{
throw new UnsupportedOperationException("Configuration is read-only!");
}
/**
* Removes all properties from this configuration. Because this
* configuration is read-only, this operation is not allowed and will cause
* an exception.
*/
public void clear()
{
throw new UnsupportedOperationException("Configuration is read-only!");
}
/**
* Extracts environment properties on a JRE < 1.5. This implementation
* uses ant for this purpose.
*/
void extractProperties14()
{
extractPropertiesFromCollection(Execute.getProcEnvironment());
}
/**
* An internally used method for processing a collection with environment
* entries. The collection must contain strings like
* property=value. Such a collection is returned by ant.
*
* @param env the collection with the properties
*/
void extractPropertiesFromCollection(Collection env)
{
environment = new HashMap();
for (Iterator it = env.iterator(); it.hasNext();)
{
String entry = (String) it.next();
int pos = entry.indexOf('=');
if (pos == -1)
{
getLogger().warn("Ignoring: " + entry);
}
else
{
environment.put(entry.substring(0, pos), entry
.substring(pos + 1));
}
}
}
/**
* Extracts environment properties on a JR >= 1.5. From this Java version
* on, there is an official way of doing this. However because the code
* should compile on lower Java versions, too, we have to invoke the method
* using reflection.
*/
void extractProperties15()
{
try
{
Method method = System.class.getMethod(METHOD_NAME, null);
environment = (Map) method.invoke(null, null);
}
catch (Exception ex)
{
// this should normally not happen on a JRE >= 1.5
throw new ConfigurationRuntimeException(
"Error when accessing environment properties", ex);
}
}
}