Package jcckit.util

Class FlatConfigData

java.lang.Object

jcckit.util.FlatConfigData

All Implemented Interfaces:

ConfigData

Direct Known Subclasses:

AppletBasedConfigData, PropertiesBasedConfigData

public abstract class FlatConfigData
extends Object
implements ConfigData

An implementation of ConfigData based on a flat representation of the hierachically organized key-value pairs. Concrete subclasses must implement the methods getValue(java.lang.String) and createConfigData(java.lang.String) in accordance with the Template Method pattern and Factory Method pattern, respectively.

In a flat representation of hierachically organized key-value pairs all key-value pairs are stored in a single Hashtable. Its key is the full key of the configuration data (i.e. the key including its path).

Example (using the notation for a .properties file):

  title = example
  symbolAttributes/className = jcckit.graphic.BasicDrawingAttributes
  symbolAttributes/fillColor = 0xcaffee
  symbolAttributes/lineColor = 0xff0000
  

The following table shows the result of some method calls at a FlatConfigData instance prepared with this example:

Method call	Result
get("title")	example
getNode("symbolAttributes").get("fillColor")	0xcaffee

In addition FlatConfigData implements inheritance of key-value pairs. Basically a node in the tree of key-value pairs may extend another node in the tree. The extended node inherit all key-value pairs from the extending one including the key-value pairs of all descendants. The value of a inherited key-value pair may be overridden. Also new key-value pairs may be placed in the inherited node or anywhere in the subtree. Note, that the extending node has to be a node which is not a descendant of the extended node (otherwise a circulary chain of references occurs). As a consequence not more than 20 inheritance levels are allowed.

The implementation of this kind of inheritance in a flat hashtable is done by an additional key-value pair of the form

    extending-node/ = extended-node/
  

Example:

  A/a/priority = high
  A/a/alpha/hello = universe
  A/a/alpha/answer = 42
  A/b/1/ = A/a/
  A/b/1/alpha/hello = world
  A/b/1/alpha/question = 6 * 7
  

The following table shows the result of various method calls applied at the node A/b/1/ of a FlatConfigData instance prepared with this example:

Method call	Result	Comment
get("priority")	high	inherited
getNode("alpha").get("hello")	world	overridden
getNode("alpha").get("question")	6 * 7	added
getNode("alpha").get("answer")	42	inherited

Author:

Franz-Josef Elmer

Constructor Summary

Constructors

Constructor	Description
FlatConfigData(String path)	Creates a new instance for the specified path.

Method Summary

Modifier and Type	Method	Description
protected abstract ConfigData	createConfigData(String path)	Returns the FlatConfigData object for the specified full path.
String	get(String key)	Returns the value associated with this key.
String	getFullKey(String key)	Returns the full key.
ConfigData	getNode(String key)	Returns the ConfigData object associated with this key.
protected abstract String	getValue(String fullKey)	Returns the value for the specified full key from the flat representation of the hierarchically organized key-value pairs.

Methods inherited from class java.lang.Object

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

Constructor Detail

FlatConfigData

public FlatConfigData(String path)

Creates a new instance for the specified path.

Method Detail

getFullKey

public String getFullKey(String key)

Returns the full key.

Specified by:

getFullKey in interface ConfigData

Parameters:

key - A (relative) key. null is not allowed.

Returns:

the path concatenated with key or key if the path is undefined.

get

public String get(String key)

Returns the value associated with this key.

Specified by:

get in interface ConfigData

Parameters:

key - The relative key. null is not allowed.

Returns:

the associated value. Will be null if no value exists for key.

getNode

public ConfigData getNode(String key)

Returns the ConfigData object associated with this key.

Specified by:

getNode in interface ConfigData

Parameters:

key - The relative key.

Returns:

the associated value. Will never return null. Instead an empty ConfigData is returned.

getValue

protected abstract String getValue(String fullKey)

Returns the value for the specified full key from the flat representation of the hierarchically organized key-value pairs.

Parameters:

fullKey - The full key including path. null is not allowed.

Returns:

the value or null if not found.

createConfigData

protected abstract ConfigData createConfigData(String path)

Returns the FlatConfigData object for the specified full path. In general path will be used in the constructor with path argument.

Parameters:

path - The full path.

Returns:

a new instance in any case.