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Topic: Delegation pattern

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	Delegation pattern - Wikipedia, the free encyclopedia
		In software engineering, the delegation pattern is a technique where an object outwardly expresses certain behaviour but in reality delegates responsibility for implementing that behavior to an associated object in an Inversion of Responsibility.
		The delegation pattern is the fundamental abstraction that underpins composition (also referred to as aggregation), mixins and aspects.
		This pattern typically sacrifices speed optimization in favor of enhanced clarity of abstraction.
	en.wikipedia.org /wiki/Delegation_pattern (563 words)

	Design Pattern Synopses
		Delegation is a way of extending and reusing a class by writing another class with additional functionality that uses instances of the original class to provide the original functionality.
		The Filter pattern is a special case of the Decorator pattern, where a data source or data sink object is wrapped to add logic to the handling of a data stream.
		The Composite pattern also allows the objects in the tree to be manipulated in a consistent manner, by requiring all of the objects in the tree to have a common superclass or interface.
	www.mindspring.com /~mgrand/pattern_synopses.htm (4381 words)

	patterns_java (Site not responding. Last check: 2007-10-22)
		The Heartbeat pattern may be used with the Two Phase Commit pattern to ensure that the Coordinator object is able to detect catastrophic failures of component transactions in a bounded amount of time.
		The Virtual Proxy pattern, described in Volume 1, may be used by an implementation of the Persistence Layer pattern to defer the fetching of objects that are part of a more complext object but may not be needed for some uses of the complex object.
		The Change Manager pattern is often used with the persistence pattern in order to determine, based on the state of an object whether it needs to be written to the persistent store or not.
	www.selectorweb.com /patterns_all.html (12763 words)

	Composite pattern - Wikipedia, the free encyclopedia
		In Computer Science, the composite pattern is a design pattern: "A general solution to a common problem in software design."
		B makes for shorter code and less typing when the relationship between the objects is not likely to change.
		The methods that propagate requests to them are "delegate methods".
	en.wikipedia.org /wiki/Composite_pattern (587 words)

	JOT: Journal of Object Technology - CentiJ: An RMI Code Generator (Site not responding. Last check: 2007-10-22)
		In manual static delegation, an instance is passed to a proxy class as a parameter.
		Delegation has long been thought of as a generalization of inheritance (a point of view with which there is disagreement) [Aksit 1991] [Bracha].
		Lieberman indicated that delegation is considered safer than inheritance because it forces the programmer to select which method to use when identical methods are available in two delegate classes.
	www.jot.fm /issues/issue_2002_11/article2 (6502 words)

	Patterns assignments
		A use of the Bridge pattern is to dynamically change the implementation of an object.
		The Event Delegation Model of Java 1.0 adopts the Chain of Responsibility pattern to dispatch events to event handlers.
		The Visitor pattern is one of the most important --- and most difficult patterns to understand and use.
	www.cs.pdx.edu /~aggarwaa/java_patterns/assignments.html (4459 words)

	jGuru: When would I use the delegation pattern instead of inheritence to extend a class's behavior?
		Delegation can be viewed as a relationship between objects where one object forwards certain method calls to another object, called its delegate.
		With delegation, a Window object would maintain a reference or pointer to a Rectangle object, and calls to rectangle-like methods of the Window object would be delegated to corresponding methods of the Rectangle object.
		Sometimes, the choice between delegation and inheritance is driven by external factors such as programming language support for multiple inheritance or design constraints requiring polymorphism.
	www.jguru.com /faq/view.jsp?EID=27916 (1005 words)

	OSNews.com
		Dynamic Delegation is a little known feature of Java that gives it the power to do some very flexible things (sort of like Smalltalk's "cannotunderstand" message handler).
		The "delegation pattern" really just means to wrap a method from another class, using the same name and no additional code.
		Delegation is also used to enhance basic classes at runtime with extra features.
	www.osnews.com /comment.php?news_id=9005 (904 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		A person reading code that uses delegation will be more likely to understand the role that the objects play if the roles are part of a well know pattern or a pattern the recurs frequently in your program.
		For example if multiple classes delegate the creation of widget objects, the role of the delegatee object becomes more obvious if all of the classes that delegate that operation refer to delegatee objects through a variable called }{\cs67\f2\fs20\lang1024 widgetFactory}{.
		Instances of those classes delegate to instances of }{\cs67\f2\fs20\lang1024 AWTEventMulticaster}{ the responsibility of remembering what objects are listening for the events that they produce and also the responsibility of sending an event to all of those objects.
	www.laputan.org /pub/patterns/grand/Fundamental.doc (1432 words)

	ONJava.com -- Dynamic Delegation and Its Applications
		//The delegation class is a sub-class of the class to be delegated public class TestBeanDelegation extends TestBean implements Delegation { //The object to be delegated TestBean bean; //The invocation handler DelegationInvocationHandler handler;...
		Since the generated delegation class takes the given class as its superclass, it is illegal to specify more than one class.
		is an interface defining all of the delegation behaviors and is expected to be implemented by the client's developer.
	www.onjava.com /pub/a/onjava/2004/11/17/dunamis.html (543 words)

	Wikinfo \| Design pattern (computer science)
		Design patterns are lessons that have been accumulated in the community of computer programming.
		A design pattern is an abstraction of the best solutions for a particular class of problems.
		It is important that patterns accompany a name because it makes possible to describe problems, solutions and talk about them with other folks.
	www.wikinfo.org /wiki.php?title=Design_pattern_(computer_science) (463 words)

	delegation concept from the Object Oriented Software Engineering knowledge base (Site not responding. Last check: 2007-10-22)
		It would be better to ensure that only one method in the «Delegator» calls the method in the «Delegate».
		By 'neighbouring', we mean the «Delegate» is connected to the «Delegator» by an association.
		Normally, in order to use delegation an association should already exist between the «Delegator» and the «Delegate».
	www.site.uottawa.ca:4321 /oose/delegation.html (428 words)

	jGuru: Patterns FAQ (Site not responding. Last check: 2007-10-22)
		A complete discussion of even a small pattern is beyond the scope of a simple FAQ entry, but it is possible to get the idea by examining an abbreviated discussion of one of the simplest and most easily understood patterns.
		Certainly this pattern is used in activating/passivating the enterprise beans by the container/server.
		The evictor pattern was originated by IONA Technologies (the makers of the Orbix ORB) as a way of managing the growth of object instances (and associated memory) in a pre-POA CORBA server.
	www.jguru.com /faq/printablefaq.jsp?topic=Patterns (11385 words)

	3.4 Traits
		This is significant because cloning an object with a traits delegation slot will result in a new object with the same object delegated-to, so all methods defined on that traits object apply to the new clone.
		If mixins are given, it will include more immutable delegation links between the new traits and the traits of the array's objects, in the given order, which achieves a structured, shared behavior of static multiple delegation.
		Finally, it will compare the delegation pattern of the new object with the old, and only replace the old if they differ.
	slate.tunes.org /doc/progman/node18.html (588 words)

	New Page 1 (Site not responding. Last check: 2007-10-22)
		The strategy pattern is a typical example of a software design pattern: it separates things that change from things that do not change.
		Command patterns "encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operation." (Gamma, et al.
		Command pattern behavior is similar to a callback function and to a pointer to this function (C and C++).
	www.enel.ucalgary.ca /~cervatiu/609_04/week3.htm (495 words)

	JOT: Journal of Object Technology - Asynchronous RMI for CentiJ, Douglas Lyon (Site not responding. Last check: 2007-10-22)
		CentiJ is a software synthesis system that, until recently, used synchronous, semi-automatic static proxy delegation to help in the automation of the creation of distributed Java programs on NOWS (Networks of Workstations).
		Delegation has been cited as a mechanism to obtain implementation inheritance via composition [21] [22].
		He indicated that delegation is considered safer than inheritance because it forces the programmer to select which method to use when identical methods are available in two delegate classes.
	www.jot.fm /issues/issue_2004_03/column5 (3750 words)

	[No title]
		The Singleton Pattern (Gang of Four)¡40Z""ª ¨ÁContext: It is very common to find classes for which only one instance should exist (singleton) Examples: a Main Window; Company or University class.
		The Observer Pattern (Gang of Four)¡00""ª ¨&Second in the gang-of-four patterns (Singleton was the first) This is another VERY popular one.
		The Adapter Pattern (Gang of Four)¡0/""ª ¨ºContext: You are building an inheritance hierarchy and want to incorporate it into an existing class.
	www.unf.edu /~broggio/cen6017/classnotes/36.DesignPatterns.ppt (761 words)

	Inheritance as aStatic Pattern of Message Passing
		's support for message delegation allows us to build inheritance as a pattern of message passing.
		We call this pattern static delegation to distinguish it from other patterns of inheritance by delegation [ref Treaty of Orlando, Lieberman, Vulcan, Self, Clarity].
		The first part of the above code, shown in bold, is boilerplate that would need to be manually repeated whenever this inheritance pattern is used.
	www.erights.org /elang/blocks/inheritance.html (697 words)

	Applying Patterns to JDBC Development @ JAVA DEVELOPER'S JOURNAL (Site not responding. Last check: 2007-10-22)
		Unlike what you find in some pattern books (although most I've read are excellent), I wanted to create a practical piece of code that uses both patterned design and patterned implementation not another "gutted" bank application but an actual piece of code that could be used in a real-world business application.
		Thus the gang also recommends that patterns be placed into certain pattern "classifications" based on principles such as the pattern's purpose and scope.
		I've limited the description of the patterns I use in the code example to a few "consolidated descriptives" that should provide enough information for you to grasp their meaning without my going into pages of detail.
	jdj.sys-con.com /read/36415.htm (4733 words)

	Trace Manager Patterns (Site not responding. Last check: 2007-10-22)
		We thought we might be a candidate for a Singleton Pattern.
		Originally we thought that we might be part of some Delegation pattern.
		We thought an interesting pattern to be used for the overall system would be the Mediator pattern.
	coweb.cc.gatech.edu /cs4330/400 (158 words)

	Linda Rising - Patterns Almanac - Smalltalk Scaffolding Patterns (Site not responding. Last check: 2007-10-22)
		Override the doesNotUnderstand: method of the delegator class to iterate through its attributes, looking for an attribute that supports the method selector that was not understood.
		To identify the implicit behavior and make it part of the explicit behavior of the class, override the doesNotUnderstand: method, substituting code to generate explicit methods for the virtual methods invoked the first time the implicit message is sent.
		For a given event/state pair, synthesize a method selector by concatenating the state and event symbols, then dispatch based on the resulting selector.
	www.smallmemory.com /almanac/DobleEtc99.html (192 words)

	Linda Rising - Patterns Almanac - Smalltalk Best Practice Patterns
		To change the value of an instance variable, provide a method with the same name as the variable and a single parameter--the value to be set.
		To provide access to an instance variable that holds a collection, provide methods implemented using Delegation to the collection.
		This pattern can be combined with Hypoth-A-Sized Collection to create a stream whose collection won't grow.
	www.smallmemory.com /almanac/Beck97.html (2233 words)

	jGuru: Serializing Remote Objects: Server
		In this exercise you will run the Server Side of an RMI demonstration All of the files have been created for you.
		In this exercise you will see how to use the Delegation Pattern to allow a service to migrate.
		Unless otherwise licensed, code in all technical manuals herein (including articles, FAQs, samples) is provided under this License.
	java.sun.com /developer/onlineTraining/rmi/exercises/LocalRemoteServer (185 words)

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