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## org.apache.commons.configuration
Class EnvironmentConfiguration

    java.lang.Object
      org.apache.commons.configuration.event.EventSource
          org.apache.commons.configuration.AbstractConfiguration
              org.apache.commons.configuration.EnvironmentConfiguration

All Implemented Interfaces:
  Configuration

    public class EnvironmentConfiguration

extends AbstractConfiguration

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");

Since:
  1.5
Author:
  Nicolas De Loof
See Also:
  `Execute.getProcEnvironment()`

Field Summary

Fields inherited from class org.apache.commons.configuration.AbstractConfiguration
`END_TOKEN, EVENT_ADD_PROPERTY, EVENT_CLEAR, EVENT_CLEAR_PROPERTY, EVENT_READ_PROPERTY, EVENT_SET_PROPERTY, START_TOKEN`

Constructor Summary
`EnvironmentConfiguration()` Constructor.

Method Summary
`protected void` | `addPropertyDirect(String key, Object value)` Adds a property to this configuration.
`void` | `clear()` Removes all properties from this configuration.
`void` | `clearProperty(String key)` Removes a property from this configuration.
`boolean` | `containsKey(String key)` Check if the configuration contains the specified key.
`Iterator` | `getKeys()` Get the list of the keys contained in the configuration.
`Object` | `getProperty(String key)` Gets a property from the configuration.
`boolean` | `isEmpty()` Check if the configuration is empty.

Methods inherited from class org.apache.commons.configuration.AbstractConfiguration
`addErrorLogListener, addProperty, append, clearPropertyDirect, copy, createInterpolator, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getDefaultListDelimiter, getDelimiter, getDouble, getDouble, getDouble, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getInterpolator, getKeys, getList, getList, getListDelimiter, getLogger, getLong, getLong, getLong, getProperties, getProperties, getShort, getShort, getShort, getString, getString, getStringArray, getSubstitutor, interpolate, interpolate, interpolatedConfiguration, interpolateHelper, isDelimiterParsingDisabled, isScalarValue, isThrowExceptionOnMissing, resolveContainerStore, setDefaultListDelimiter, setDelimiter, setDelimiterParsingDisabled, setListDelimiter, setLogger, setProperty, setThrowExceptionOnMissing, subset`

Methods inherited from class org.apache.commons.configuration.event.EventSource
`addConfigurationListener, addErrorListener, clearConfigurationListeners, clearErrorListeners, clone, createErrorEvent, createEvent, fireError, fireEvent, getConfigurationListeners, getErrorListeners, isDetailEvents, removeConfigurationListener, removeErrorListener, setDetailEvents`

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### EnvironmentConfiguration

    public EnvironmentConfiguration()

  Constructor.

Method Detail

### addPropertyDirect

    protected void addPropertyDirect(String key,
                                     Object value)

  Adds a property to this configuration. Because this configuration is read-only, this operation is not allowed and will cause an exception.

  Specified by:
    `addPropertyDirect` in class `AbstractConfiguration`
  Parameters:
    `key` - the key of the property to be added
    `value` - the property value

### containsKey

    public boolean containsKey(String key)

  Check if the configuration contains the specified key.

  Parameters:
    `key` - the key whose presence in this configuration is to be tested
  Returns:
    `true` if the configuration contains a value for this key, `false` otherwise
  See Also:
    `Configuration.containsKey(java.lang.String)`

### getKeys

    public Iterator getKeys()

  Get the list of the keys contained in the configuration. The returned iterator can be used to obtain all defined keys. Note that the exact behavior of the iterator's `remove()` method is specific to a concrete implementation. It may remove the corresponding property from the configuration, but this is not guaranteed. In any case it is no replacement for calling ``Configuration.clearProperty(String)`` for this property. So it is highly recommended to avoid using the iterator's `remove()` method.

  Returns:
    An Iterator.
  See Also:
    `Configuration.getKeys()`

### getProperty

    public Object getProperty(String key)

  Gets a property from the configuration. This is the most basic get method for retrieving values of properties. In a typical implementation of the `Configuration` interface the other get methods (that return specific data types) will internally make use of this method. On this level variable substitution is not yet performed. The returned object is an internal representation of the property value for the passed in key. It is owned by the `Configuration` object. So a caller should not modify this object. It cannot be guaranteed that this object will stay constant over time (i.e. further update operations on the configuration may change its internal state).

  Parameters:
    `key` - property to retrieve
  Returns:
    the value to which this configuration maps the specified key, or null if the configuration contains no mapping for this key.
  See Also:
    `Configuration.getProperty(java.lang.String)`

### isEmpty

    public boolean isEmpty()

  Check if the configuration is empty.

  Returns:
    `true` if the configuration contains no property, `false` otherwise.
  See Also:
    `Configuration.isEmpty()`

### clearProperty

    public void clearProperty(String key)

  Removes a property from this configuration. Because this configuration is read-only, this operation is not allowed and will cause an exception.

  Specified by:
    `clearProperty` in interface `Configuration`
  Overrides:
    `clearProperty` in class `AbstractConfiguration`
  Parameters:
    `key` - the key of the property to be removed

### clear

    public void clear()

  Removes all properties from this configuration. Because this configuration is read-only, this operation is not allowed and will cause an exception.

  Specified by:
    `clear` in interface `Configuration`
  Overrides:
    `clear` in class `AbstractConfiguration`

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