org.apache.commons.configuration
Class SubsetConfiguration

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

All Implemented Interfaces:

Configuration

public class SubsetConfiguration

extends AbstractConfiguration

A subset of another configuration. The new Configuration object contains every key from the parent Configuration that starts with prefix. The prefix is removed from the keys in the subset.

It is usually not necessary to use this class directly. Instead the Configuration.subset(String) method should be used, which will return a correctly initialized instance.

Version:

$Revision: 439648 $, $Date: 2006-09-02 22:42:10 +0200 (Sa, 02 Sep 2006) $

Author:

Emmanuel Bourg

Field Summary

protected String	delimiter The prefix delimiter
protected Configuration	parent The parent configuration.
protected String	prefix The prefix used to select the properties.

Fields inherited from class org.apache.commons.configuration.AbstractConfiguration

END_TOKEN, EVENT_ADD_PROPERTY, EVENT_CLEAR, EVENT_CLEAR_PROPERTY, EVENT_SET_PROPERTY, START_TOKEN

Constructor Summary

SubsetConfiguration(Configuration parent, String prefix)
Create a subset of the specified configuration

SubsetConfiguration(Configuration parent, String prefix, String delimiter)
Create a subset of the specified configuration

Method Summary

void	addPropertyDirect(String key, Object value) Adds a key/value pair to the Configuration. Override this method to provide write acces to underlying Configuration store.
void	clearProperty(String key) Removes the specified property from this configuration. This implementation performs some preparations and then delegates to clearPropertyDirect(), which will do the real work.
boolean	containsKey(String key) Check if the configuration contains the specified key.
protected String	getChildKey(String key) Return the key in the subset configuration associated to the specified key in the parent configuration.
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.
Iterator	getKeys(String prefix) Get the list of the keys contained in the configuration that match the specified prefix.
Configuration	getParent() Return the parent configuation for this subset.
protected String	getParentKey(String key) Return the key in the parent configuration associated to the specified key in this subset.
String	getPrefix() Return the prefix used to select the properties in the parent configuration.
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).
protected String	interpolate(String base) interpolate key names to handle ${key} stuff
boolean	isEmpty() Check if the configuration is empty.
boolean	isThrowExceptionOnMissing() Returns true if missing values throw Exceptions. The subset inherits this feature from its parent if it supports this feature.
void	setPrefix(String prefix) Set the prefix used to select the properties in the parent configuration.
void	setProperty(String key, Object value) Set a property, this will replace any previously set values. Set values is implicitly a call to clearProperty(key), addProperty(key, value).
void	setThrowExceptionOnMissing(boolean throwExceptionOnMissing) Allows to set the throwExceptionOnMissing flag. This flag controls the behavior of property getter methods that return objects if the requested property is missing. If the flag is set to false (which is the default value), these methods will return null. If set to true, they will throw a NoSuchElementException exception. Note that getter methods for primitive data types are not affected by this flag. Change the behaviour of the parent configuration if it supports this feature.
Configuration	subset(String prefix) Return a decorator Configuration containing every key from the current Configuration that starts with the specified prefix. The prefix is removed from the keys in the subset. For example, if the configuration contains the following properties: prefix.number = 1 prefix.string = Apache prefixed.foo = bar prefix = Jakarta the Configuration returned by subset("prefix") will contain the properties: number = 1 string = Apache = Jakarta (The key for the value "Jakarta" is an empty string) Since the subset is a decorator and not a modified copy of the initial Configuration, any change made to the subset is available to the Configuration, and reciprocally.

Methods inherited from class org.apache.commons.configuration.AbstractConfiguration

addProperty, clear, clearPropertyDirect, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getDefaultListDelimiter, getDelimiter, getDouble, getDouble, getDouble, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getList, getList, getListDelimiter, getLong, getLong, getLong, getProperties, getProperties, getShort, getShort, getShort, getString, getString, getStringArray, interpolate, interpolateHelper, isDelimiterParsingDisabled, resolveContainerStore, setDefaultListDelimiter, setDelimiter, setDelimiterParsingDisabled, setListDelimiter

Methods inherited from class org.apache.commons.configuration.event.EventSource

addConfigurationListener, clearConfigurationListeners, createEvent, fireEvent, getConfigurationListeners, isDetailEvents, removeConfigurationListener, setDetailEvents

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

parent

protected Configuration parent

The parent configuration.

prefix

protected String prefix

The prefix used to select the properties.

delimiter

protected String delimiter

The prefix delimiter

Constructor Detail

SubsetConfiguration

public SubsetConfiguration(Configuration parent,
                           String prefix)

Create a subset of the specified configuration

Parameters:

parent - The parent configuration

prefix - The prefix used to select the properties

SubsetConfiguration

public SubsetConfiguration(Configuration parent,
                           String prefix,
                           String delimiter)

Create a subset of the specified configuration

Parameters:

parent - The parent configuration

prefix - The prefix used to select the properties

delimiter - The prefix delimiter

Method Detail

getParentKey

protected String getParentKey(String key)

Return the key in the parent configuration associated to the specified key in this subset.

Parameters:

key - The key in the subset.

Returns:

the key as to be used by the parent

getChildKey

protected String getChildKey(String key)

Return the key in the subset configuration associated to the specified key in the parent configuration.

Parameters:

key - The key in the parent configuration.

Returns:

the key in the context of this subset configuration

getParent

public Configuration getParent()

Return the parent configuation for this subset.

Returns:

the parent configuration

getPrefix

public String getPrefix()

Return the prefix used to select the properties in the parent configuration.

Returns:

the prefix used by this subset

setPrefix

public void setPrefix(String prefix)

Set the prefix used to select the properties in the parent configuration.

Parameters:

prefix - the prefix

subset

public Configuration subset(String prefix)

Return a decorator Configuration containing every key from the current Configuration that starts with the specified prefix. The prefix is removed from the keys in the subset. For example, if the configuration contains the following properties:

    prefix.number = 1
    prefix.string = Apache
    prefixed.foo = bar
    prefix = Jakarta

the Configuration returned by subset("prefix") will contain the properties:

    number = 1
    string = Apache
    = Jakarta

(The key for the value "Jakarta" is an empty string)

Since the subset is a decorator and not a modified copy of the initial Configuration, any change made to the subset is available to the Configuration, and reciprocally.

Specified by:

subset in interface Configuration

Overrides:

subset in class AbstractConfiguration

isEmpty

public boolean isEmpty()

Check if the configuration is empty.

Specified by:

isEmpty in interface Configuration

Specified by:

isEmpty in class AbstractConfiguration

containsKey

public boolean containsKey(String key)

Check if the configuration contains the specified key.

Specified by:

containsKey in interface Configuration

Specified by:

containsKey in class AbstractConfiguration

addPropertyDirect

public void addPropertyDirect(String key,
                              Object value)

Adds a key/value pair to the Configuration. Override this method to provide write acces to underlying Configuration store.

Specified by:

addPropertyDirect in class AbstractConfiguration

Parameters:

key - key to use for mapping

value - object to store

setProperty

public void setProperty(String key,
                        Object value)

Set a property, this will replace any previously set values. Set values is implicitly a call to clearProperty(key), addProperty(key, value).

Specified by:

setProperty in interface Configuration

Overrides:

setProperty in class AbstractConfiguration

clearProperty

public void clearProperty(String key)

Removes the specified property from this configuration. This implementation performs some preparations and then delegates to clearPropertyDirect(), which will do the real work.

Specified by:

clearProperty in interface Configuration

Overrides:

clearProperty in class AbstractConfiguration

Parameters:

key - the key to be removed

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.

getKeys

public Iterator getKeys(String prefix)

Get the list of the keys contained in the configuration that match the specified prefix.

Specified by:

getKeys in interface Configuration

Overrides:

getKeys in class AbstractConfiguration

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.

Specified by:

getKeys in interface Configuration

Specified by:

getKeys in class AbstractConfiguration

interpolate

protected String interpolate(String base)

interpolate key names to handle ${key} stuff

Overrides:

interpolate in class AbstractConfiguration

Parameters:

base - string to interpolate

Returns:

returns the key name with the ${key} substituted

setThrowExceptionOnMissing

public void setThrowExceptionOnMissing(boolean throwExceptionOnMissing)

Allows to set the throwExceptionOnMissing flag. This flag controls the behavior of property getter methods that return objects if the requested property is missing. If the flag is set to false (which is the default value), these methods will return null. If set to true, they will throw a NoSuchElementException exception. Note that getter methods for primitive data types are not affected by this flag. Change the behaviour of the parent configuration if it supports this feature.

Overrides:

setThrowExceptionOnMissing in class AbstractConfiguration

Parameters:

throwExceptionOnMissing - The new value for the property

isThrowExceptionOnMissing

public boolean isThrowExceptionOnMissing()

Returns true if missing values throw Exceptions. The subset inherits this feature from its parent if it supports this feature.

Overrides:

isThrowExceptionOnMissing in class AbstractConfiguration

Returns:

true if missing values throw Exceptions