PropertiesList (Brazil 2.3)

A PropertiesList instance is intended to be an element of a doubly linked list consisting of other PropertiesList instances. Each PropertiesList instance "wraps" a Dictionary object. A PropertiesList is a subclass of Properties and therefore provides the same API, including the methods and fields of Dictionary and Hashtable. The PropertiesList class overrides all methods of the Properties API and delegates the method evaluation to the wrapped Properties object.

The linked list of PropertiesList objects is constructed by Request for each incoming request. That is, there is a unique PropertiesList linked list for each request. The head of the initial list constructed by request is Request.props and the tail of the two element list is Request.serverProps. The former wraps an empty Properties object, while the latter wraps Server.props. Other PropertiesList objects can be added, and removed, from this initial list as required.

Given a reference to a PropertiesList object on the linked list (e.g. request.props), one typically "looks up" the value associated with a name using the getProperty method, which delegates to the wrapped Properties.getProperty method. If the result is null, meaning the name/value pair is not stored in the wrapped Properties object, the request is "forwarded" to the next object on the linked list, and so on until either the name/value pair is found (and the value is returned) or the end of the list is reached (and null is returned).

It may be desirable for the name/value lookup to be delayed until after the lookup request has been passed on to subsequent objects on the list. This can be done by using the two parameter constructor and setting the second, boolean, parameter to true. Then the getProperty request is forwarded to the next object in the list rather than delegated to the wrapped Properties object. If the result of the forwarded request is null, the request is then passed to the wrapped Properties object and it's result is returned.

Version: 2.8

Author: Steve Drach <drach@sun.com>

See Also: java.util.Dictionary java.util.Hashtable java.util.Properties

Field Summary
static boolean	debug Set `true` to turn on debug output.

Constructor Summary
	PropertiesList() Constructs a new `PropertiesList` object that wraps an empty new `Properties` object.
	PropertiesList(Dictionary dict) Constructs a new `PropertiesList` object that wraps the input `Dictionary`.
	PropertiesList(Dictionary dict, boolean searchNextFirst) Constructs a new `PropertiesList` object that wraps the input `Dictionary`.

Method Summary
void	addAfter(PropertiesList cursor) Adds this `PropertiesList` object into a linked list following the object referenced by the `cursor` parameter.
void	addBefore(PropertiesList cursor) Adds this `PropertiesList` object into a linked list preceding the object referenced by the `cursor` parameter.
void	clear() Invokes the same method on the wrapped `Hashtable` object.
Object	clone() Invokes the same method on the wrapped `Hashtable` object.
boolean	contains(Object value) Invokes the same method on the wrapped `Hashtable` object.
boolean	containsKey(Object key) Invokes the same method on the wrapped `Hashtable` object.
void	dump(boolean full, String msg) Starting with this object, print the contents of this and succeeding objects that are on the same list as this object is.
Enumeration	elements() Invokes the same method on the wrapped `Dictionary` object.
Set	entrySet() Invokes the same method on the wrapped `Hashtable` object.
boolean	equals(Object o) Invokes the same method on the wrapped `Hashtable` object.
Object	get(Object key) Invokes the same method on the wrapped `Dictionary` object.
PropertiesList	getHead() Returns the `PropertiesList` object that is the first object on the list of which this object is a member.
PropertiesList	getNext() Returns the `PropertiesList` object that succedes this object on the list of which this object is a member.
PropertiesList	getPrior() Returns the `PropertiesList` object that precedes this object on the list of which this object is a member.
String	getProperty(String key) Looks up `key` in the wrapped object.
String	getProperty(String key, String defaultValue) Uses `getProperty(String)` to look up the value associated with the key.
Dictionary	getWrapped() Returns the `Dictionary` object wrapped by this `PropertiesList`.
int	hashCode() Invokes the same method on the wrapped `Hashtable` object.
boolean	isEmpty() Invokes the same method on the wrapped `Dictionary` object.
boolean	isTransient() Sub-classes of PropertiesList can override this to mark themselves "transient", in which case `addAfter` will skip this list.
Enumeration	keys() Invokes the same method on the wrapped `Dictionary` object.
Set	keySet() Invokes the same method on the wrapped `Hashtable` object.
void	list(PrintStream out) Invokes the same method on the wrapped `Properties` object.
void	list(PrintWriter out) Invokes the same method on the wrapped `Properties` object.
void	load(InputStream in) Invokes the same method on the wrapped `Properties` object.
Enumeration	propertyNames() Invokes the same method on the wrapped `Properties` object.
Enumeration	propertyNames(String pattern) Returns an `Enumeration` of property names that match a `glob` pattern.
Object	put(Object key, Object value) Invokes the same method on the wrapped `Dictionary` object.
void	putAll(Map t) Invokes the same method on the wrapped `Hashtable` object.
boolean	remove() Remove this object from the list in which it's a member.
Object	remove(Object key) Invokes the same method on the wrapped `Dictionary` object.
boolean	removeProperty(String key, boolean all) Remove a property from a a chain of properties lists. if "all" is specified, then remove all the keys and values from all property lists in the chain instead of just the first one found.
boolean	removeProperty(String key) Remove the key and its associated value from the first properties object in the chain that contains this key.
void	save(OutputStream out, String header) Invokes the same method on the wrapped `Properties` object.
Object	setProperty(String key, String value) Invokes the same method on the wrapped `Properties` object if it exists.
int	size() Invokes the same method on the wrapped `Dictionary` object.
void	store(OutputStream out, String header) Invokes the same method on the wrapped `Properties` object.
String	toString() Returns a `String` containing the `System.identityHashCode`s of this object, the wrapped object, and the preceding and succeding objects on the list of which this object is a member.
Collection	values() Invokes the same method on the wrapped `Hashtable` object.
PropertiesList	wraps(Dictionary d) Find the first `PropertiesList` object on the list of which this object is a member that wraps the `Dictionary` parameter.

Constructs a new PropertiesList object that wraps the input Dictionary. If the boolean parameter is set true, the wrapped Dictionary is searched after subsequent PropertiesList objects in the linked list are searched, and only if the result of that search was null.

Parameters: dict The Dictionary object wrapped by this PropertiesList. searchNextFirst If true all the following objects in the list are searched before this one.

Looks up key in the wrapped object. If the result is null the request is forwarded to the succeeding object in the list of which this object is a member. If the search order was changed by constructing this object with the two parameter constructor, the request is first forwarded and then, if the result of the forwarded request is null, the key is looked up in the wrapped Properties object.

Parameters: key The key whose value is sought.

Returns: The value or null.

Class PropertiesList