CPSC 410

 Build on previous Connector lectures  Learn how to implement flexible connector implementations  Learn the Dependency Injection pattern  Learn the basics of Java Reflection

 A methodology for software design to provide plugin-based extensibility  Each application class (i.e. domain type) refers to (depends on) other application classes only through interfaces  Classes use Factory to obtain references to dependencies

 Concrete types of interfaces are decided by configuration files  Allows the wrapper-oriented patterns to be applied at any time  Wrapper-oriented patterns: ◦ Decorator ◦ Adaptor ◦ Proxy ◦ …

 a class that provides methods which generally forwards responsibility for application- specific feature implementation to another object called the delegate  has a delegate  application-generic connector features are implemented by the delegator ◦ before forwarding to the delegate ◦ after forwarding to the delegate

 extends Delegator  implements the same interface as it’s delegate ◦ implements T where T is the type of the delegate  acts as a transparent layer where connector features can be inserted  example: AccountSecurityDecorator

 extends Delegator  implements a different interface as it’s delegate ◦ implements T where T is not the type of the delegate  mediates between connector differences of T and the delegate type  Example: AccountAdaptor

 implements some application type T  forwards responsibility for implementation of T over a network  example: AccountRemoteProxy

 Creates instances of an application type that are wrapped by any number of Delegators given in a configuration file  Provides plug-and-play connector features without changing source code  Forms the basis of extensibility features ◦ Eclipse Plugins ◦ Firefox plugins ◦ etc…  example: SimpleDependencyInjectionFactory

 the class for objects that represent Java classes  part of the Java Reflection API ◦ helps implements programs that work on programs ◦ forms the basis for meta-programming in Java static Class forName(String name) ◦ get an object representing the class called name Object newInstance() ◦ automagically calls the no-arg constructor for the class and returns a new instance of the class

 INPUT: ◦ A sequence of Java class names: C 0 … C n  PRE-CONDITION: ◦ forall(C i ): i < n C i is a delegator for C i+1  IMPLEMENTATION: ◦ Use java.lang.Class to instantiate all C and link delegators to delegates  OUTPUT: ◦ An instance of C 0