org.apache.commons.configuration
Class ConfigurationKey

java.lang.Object
  extended byorg.apache.commons.configuration.ConfigurationKey
All Implemented Interfaces:
java.io.Serializable

public class ConfigurationKey
extends java.lang.Object
implements java.io.Serializable

A simple class that supports creation of and iteration on complex configuration keys.

For key creation the class works similar to a StringBuffer: There are several appendXXXX() methods with which single parts of a key can be constructed. All these methods return a reference to the actual object so they can be written in a chain. When using this methods the exact syntax for keys need not be known.

This class also defines a specialized iterator for configuration keys. With such an iterator a key can be tokenized into its single parts. For each part it can be checked whether it has an associated index.

Version:
$Id: ConfigurationKey.java,v 1.1.1.1 2003/12/23 15:09:05 epugh Exp $
Author:
Oliver Heger
See Also:
Serialized Form

Nested Class Summary
 class ConfigurationKey.KeyIterator
          A specialized iterator class for tokenizing a configuration key.
 
Field Summary
private static java.lang.String ATTRIBUTE_END
          Constant for an attribute end marker.
private static java.lang.String ATTRIBUTE_START
          Constant for an attribute start marker.
private static char INDEX_END
          Constant for an index end marker.
private static char INDEX_START
          Constant for an index start marker.
private static int INITIAL_SIZE
          Constant for the initial StringBuffer size.
private  java.lang.StringBuffer keyBuffer
          Holds a buffer with the so far created key.
private static char PROPERTY_DELIMITER
          Constant for a property delimiter.
 
Constructor Summary
ConfigurationKey()
          Creates a new, empty instance of ConfigurationKey.
ConfigurationKey(java.lang.String key)
          Creates a new instance of ConfigurationKey and initializes it with the given key.
 
Method Summary
 ConfigurationKey append(java.lang.String property)
          Appends the name of a property to this key.
 ConfigurationKey appendAttribute(java.lang.String attr)
          Appends an attribute to this configuration key.
 ConfigurationKey appendIndex(int index)
          Appends an index to this configuration key.
static java.lang.String attributeName(java.lang.String key)
          Extracts the name of the attribute from the given attribute key.
 ConfigurationKey commonKey(ConfigurationKey other)
          Returns a configuration key object that is initialized with the part of the key that is common to this key and the passed in key.
static java.lang.String constructAttributeKey(java.lang.String key)
          Decorates the given key so that it represents an attribute.
 ConfigurationKey differenceKey(ConfigurationKey other)
          Returns the "difference key" to a given key.
 boolean equals(java.lang.Object c)
          Checks if two ConfigurationKey objects are equal.
private  boolean hasDelimiter()
          Helper method that checks if the actual buffer ends with a property delimiter.
 int hashCode()
          Returns the hash code for this object.
static boolean isAttributeKey(java.lang.String key)
          Checks if the passed in key is an attribute key.
 ConfigurationKey.KeyIterator iterator()
          Returns an iterator for iterating over the single components of this configuration key.
 int length()
          Returns the actual length of this configuration key.
private static boolean partsEqual(ConfigurationKey.KeyIterator it1, ConfigurationKey.KeyIterator it2)
          Helper method for comparing two key parts.
private static java.lang.String removeAttributeMarkers(java.lang.String key)
          Helper method for removing attribute markers from a key.
private  void removeTrailingDelimiter()
          Removes a trailing delimiter if there is any.
 void setLength(int len)
          Sets the new length of this configuration key.
 java.lang.String toString()
          Returns a string representation of this object.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

ATTRIBUTE_START

private static final java.lang.String ATTRIBUTE_START
Constant for an attribute start marker.

See Also:
Constant Field Values

ATTRIBUTE_END

private static final java.lang.String ATTRIBUTE_END
Constant for an attribute end marker.

See Also:
Constant Field Values

PROPERTY_DELIMITER

private static final char PROPERTY_DELIMITER
Constant for a property delimiter.

See Also:
Constant Field Values

INDEX_START

private static final char INDEX_START
Constant for an index start marker.

See Also:
Constant Field Values

INDEX_END

private static final char INDEX_END
Constant for an index end marker.

See Also:
Constant Field Values

INITIAL_SIZE

private static final int INITIAL_SIZE
Constant for the initial StringBuffer size.

See Also:
Constant Field Values

keyBuffer

private java.lang.StringBuffer keyBuffer
Holds a buffer with the so far created key.

Constructor Detail

ConfigurationKey

public ConfigurationKey()
Creates a new, empty instance of ConfigurationKey.


ConfigurationKey

public ConfigurationKey(java.lang.String key)
Creates a new instance of ConfigurationKey and initializes it with the given key.

Parameters:
key - the key as a string
Method Detail

append

public ConfigurationKey append(java.lang.String property)
Appends the name of a property to this key. If necessary, a property delimiter will be added.

Parameters:
property - the name of the property to be added
Returns:
a reference to this object

appendIndex

public ConfigurationKey appendIndex(int index)
Appends an index to this configuration key.

Parameters:
index - the index to be appended
Returns:
a reference to this object

appendAttribute

public ConfigurationKey appendAttribute(java.lang.String attr)
Appends an attribute to this configuration key.

Parameters:
attr - the name of the attribute to be appended
Returns:
a reference to this object

isAttributeKey

public static boolean isAttributeKey(java.lang.String key)
Checks if the passed in key is an attribute key. Such attribute keys start and end with certain marker strings. In some cases they must be treated slightly different.

Parameters:
key - the key (part) to be checked
Returns:
a flag if this key is an attribute key

constructAttributeKey

public static java.lang.String constructAttributeKey(java.lang.String key)
Decorates the given key so that it represents an attribute. Adds special start and end markers.

Parameters:
key - the key to be decorated
Returns:
the decorated attribute key

attributeName

public static java.lang.String attributeName(java.lang.String key)
Extracts the name of the attribute from the given attribute key. This method removes the attribute markers - if any - from the specified key.

Parameters:
key - the attribute key
Returns:
the name of the corresponding attribute

removeAttributeMarkers

private static java.lang.String removeAttributeMarkers(java.lang.String key)
Helper method for removing attribute markers from a key.

Parameters:
key - the key
Returns:
the key with removed attribute markers

hasDelimiter

private boolean hasDelimiter()
Helper method that checks if the actual buffer ends with a property delimiter.

Returns:
a flag if there is a trailing delimiter

removeTrailingDelimiter

private void removeTrailingDelimiter()
Removes a trailing delimiter if there is any.


toString

public java.lang.String toString()
Returns a string representation of this object. This is the configuration key as a plain string.

Returns:
a string for this object

iterator

public ConfigurationKey.KeyIterator iterator()
Returns an iterator for iterating over the single components of this configuration key.

Returns:
an iterator for this key

length

public int length()
Returns the actual length of this configuration key.

Returns:
the length of this key

setLength

public void setLength(int len)
Sets the new length of this configuration key. With this method it is possible to truncate the key, e.g. to return to a state prior calling some append() methods. The semantic is the same as the setLength() method of StringBuffer.

Parameters:
len - the new length of the key

equals

public boolean equals(java.lang.Object c)
Checks if two ConfigurationKey objects are equal. The method can be called with strings or other objects, too.

Parameters:
c - the object to compare
Returns:
a flag if both objects are equal

hashCode

public int hashCode()
Returns the hash code for this object.

Returns:
the hash code

commonKey

public ConfigurationKey commonKey(ConfigurationKey other)
Returns a configuration key object that is initialized with the part of the key that is common to this key and the passed in key.

Parameters:
other - the other key
Returns:
a key object with the common key part

differenceKey

public ConfigurationKey differenceKey(ConfigurationKey other)
Returns the "difference key" to a given key. This value is the part of the passed in key that differs from this key. There is the following relation: other = key.commonKey(other) + key.differenceKey(other) for an arbitrary configuration key key.

Parameters:
other - the key for which the difference is to be calculated
Returns:
the difference key

partsEqual

private static boolean partsEqual(ConfigurationKey.KeyIterator it1,
                                  ConfigurationKey.KeyIterator it2)
Helper method for comparing two key parts.

Parameters:
it1 - the iterator with the first part
it2 - the iterator with the second part
Returns:
a flag if both parts are equal