org.apache.commons.configuration.tree
Class DefaultConfigurationKey

java.lang.Object
  extended by org.apache.commons.configuration.tree.DefaultConfigurationKey

public class DefaultConfigurationKey
extends java.lang.Object

A simple class that supports creation of and iteration on configuration keys supported by a DefaultExpressionEngine object.

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.

Instances of this class are always associated with an instance of DefaultExpressionEngine, from which the current delimiters are obtained. So key creation and parsing is specific to this associated expression engine.

Since:
1.3
Version:
$Id: DefaultConfigurationKey.java 439648 2006-09-02 20:42:10Z oheger $
Author:
Oliver Heger

Nested Class Summary
 class DefaultConfigurationKey.KeyIterator
          A specialized iterator class for tokenizing a configuration key.
 
Field Summary
private  DefaultExpressionEngine expressionEngine
          Stores a reference to the associated expression engine.
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.
 
Constructor Summary
DefaultConfigurationKey(DefaultExpressionEngine engine)
          Creates a new instance of DefaultConfigurationKey and sets the associated expression engine.
DefaultConfigurationKey(DefaultExpressionEngine engine, java.lang.String key)
          Creates a new instance of DefaultConfigurationKey and sets the associated expression engine and an initial key.
 
Method Summary
 DefaultConfigurationKey append(java.lang.String property)
          Appends the name of a property to this key.
 DefaultConfigurationKey append(java.lang.String property, boolean escape)
          Appends the name of a property to this key.
 DefaultConfigurationKey appendAttribute(java.lang.String attr)
          Appends an attribute to this configuration key.
 DefaultConfigurationKey appendIndex(int index)
          Appends an index to this configuration key.
 java.lang.String attributeName(java.lang.String key)
          Extracts the name of the attribute from the given attribute key.
 java.lang.String constructAttributeKey(java.lang.String key)
          Decorates the given key so that it represents an attribute.
 boolean equals(java.lang.Object c)
          Checks if two ConfigurationKey objects are equal.
private  java.lang.String escapeDelimiters(java.lang.String key)
          Escapes the delimiters in the specified string.
 DefaultExpressionEngine getExpressionEngine()
          Returns the associated default expression engine.
 int hashCode()
          Returns the hash code for this object.
private  boolean hasLeadingDelimiter(java.lang.String key)
          Helper method that checks if the specified key starts with a property delimiter.
private  boolean hasTrailingDelimiter(java.lang.String key)
          Helper method that checks if the specified key ends with a property delimiter.
 boolean isAttributeKey(java.lang.String key)
          Tests if the specified key represents an attribute according to the current expression engine.
 DefaultConfigurationKey.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  java.lang.String removeAttributeMarkers(java.lang.String key)
          Helper method for removing attribute markers from a key.
 void setExpressionEngine(DefaultExpressionEngine expressionEngine)
          Sets the associated expression engine.
 void setLength(int len)
          Sets the new length of this configuration key.
 java.lang.String toString()
          Returns a string representation of this object.
 java.lang.String trim(java.lang.String key)
          Removes delimiters at the beginning and the end of the specified key.
 java.lang.String trimLeft(java.lang.String key)
          Removes leading property delimiters from the specified key.
 java.lang.String trimRight(java.lang.String key)
          Removes trailing property delimiters from the specified key.
private  java.lang.String unescapeDelimiters(java.lang.String key)
          Unescapes the delimiters in the specified string.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

INITIAL_SIZE

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

See Also:
Constant Field Values

expressionEngine

private DefaultExpressionEngine expressionEngine
Stores a reference to the associated expression engine.


keyBuffer

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

Constructor Detail

DefaultConfigurationKey

public DefaultConfigurationKey(DefaultExpressionEngine engine)
Creates a new instance of DefaultConfigurationKey and sets the associated expression engine.

Parameters:
engine - the expression engine

DefaultConfigurationKey

public DefaultConfigurationKey(DefaultExpressionEngine engine,
                               java.lang.String key)
Creates a new instance of DefaultConfigurationKey and sets the associated expression engine and an initial key.

Parameters:
engine - the expression engine
key - the key to be wrapped
Method Detail

getExpressionEngine

public DefaultExpressionEngine getExpressionEngine()
Returns the associated default expression engine.

Returns:
the associated expression engine

setExpressionEngine

public void setExpressionEngine(DefaultExpressionEngine expressionEngine)
Sets the associated expression engine.

Parameters:
expressionEngine - the expression engine (must not be null)

append

public DefaultConfigurationKey append(java.lang.String property,
                                      boolean escape)
Appends the name of a property to this key. If necessary, a property delimiter will be added. If the boolean argument is set to true, property delimiters contained in the property name will be escaped.

Parameters:
property - the name of the property to be added
escape - a flag if property delimiters in the passed in property name should be escaped
Returns:
a reference to this object

append

public DefaultConfigurationKey append(java.lang.String property)
Appends the name of a property to this key. If necessary, a property delimiter will be added. Property delimiters in the given string will not be escaped.

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

appendIndex

public DefaultConfigurationKey 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 DefaultConfigurationKey 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

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.

Overrides:
equals in class java.lang.Object
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.

Overrides:
hashCode in class java.lang.Object
Returns:
the hash code

toString

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

Overrides:
toString in class java.lang.Object
Returns:
a string for this object

isAttributeKey

public boolean isAttributeKey(java.lang.String key)
Tests if the specified key represents an attribute according to the current expression engine.

Parameters:
key - the key to be checked
Returns:
true if this is an attribute key, false otherwise

constructAttributeKey

public java.lang.String constructAttributeKey(java.lang.String key)
Decorates the given key so that it represents an attribute. Adds special start and end markers. The passed in string will be modified only if does not already represent an attribute.

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

attributeName

public 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

trimLeft

public java.lang.String trimLeft(java.lang.String key)
Removes leading property delimiters from the specified key.

Parameters:
key - the key
Returns:
the key with removed leading property delimiters

trimRight

public java.lang.String trimRight(java.lang.String key)
Removes trailing property delimiters from the specified key.

Parameters:
key - the key
Returns:
the key with removed trailing property delimiters

trim

public java.lang.String trim(java.lang.String key)
Removes delimiters at the beginning and the end of the specified key.

Parameters:
key - the key
Returns:
the key with removed property delimiters

iterator

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

Returns:
an iterator for this key

hasTrailingDelimiter

private boolean hasTrailingDelimiter(java.lang.String key)
Helper method that checks if the specified key ends with a property delimiter.

Parameters:
key - the key to check
Returns:
a flag if there is a trailing delimiter

hasLeadingDelimiter

private boolean hasLeadingDelimiter(java.lang.String key)
Helper method that checks if the specified key starts with a property delimiter.

Parameters:
key - the key to check
Returns:
a flag if there is a leading delimiter

removeAttributeMarkers

private 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

unescapeDelimiters

private java.lang.String unescapeDelimiters(java.lang.String key)
Unescapes the delimiters in the specified string.

Parameters:
key - the key to be unescaped
Returns:
the unescaped key

escapeDelimiters

private java.lang.String escapeDelimiters(java.lang.String key)
Escapes the delimiters in the specified string.

Parameters:
key - the key to be escaped
Returns:
the escaped key