Lorenz: Visitor Beans:
An Aspect-Oriented Pattern
Aspect-oriented pattern: describes a solution to a tangling problem in a particular context.
AOP = control of tangling
Demeter/Java controls the following tangling problems
structure/behavior,
navigation/behavior,
behavior/behavior,
object construction/structure,
synchronization/behavior,
remote invocation/behavior.
Java Bean: a Java class
Provides: methods and events
Requires: listens to events from other beans
pcs.firePropertyChange("n", old, new)
Java Beans
Software Component Model for Java
Introspection: what methods and events are available. Builder tool can inspect a bean.
Support for customization
Events: for communication between beans
Java Beans
Three most important features
set of properties it exposes
set of methods it allows other beans to call
set of events it fires
event listeners can be associated with event source
when the event source detects something, it will call an appropriate method on the event listener object
Java Beans
Design-time versus run-time. A bean must be capable of running in a
design environment: design information, customization (code can be large: wizard style customization)
run-time environment
Clear separation:design-time and run-time aspects
Design-time interfaces can be supported in a separate class from the run-time interfaces
It is possible to deploy a bean at run-time without needing to download all its design time code
Links to remote state
Java bean runs in same address space as their container
Network access mechanisms available:
Java RMI
Java IDL: CORBA
JDBC: Java data base API
Alternate type views

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