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Reflection for Creating Decorators
in Java


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Review
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  • Reflection:
    • An object looking at its internal details at runtime (a.k.a., introspection)
  • The Decorator Pattern:
    • A decorator delegates much of its functionality to the object it decorates
An Inconvenient Aspect of the Decorator Pattern
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  • In Some Cases:
    • The interface that is realized by the decorated and the decorator contains many methods
  • The Inconvenience:
    • Every method must be implemented in the decorator
    • Most methods delegate to the decorated but they all have different signatures
Overcoming this Inconvience
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  • At Run Time:
    • Nothing can be done
  • At Compile Time:
    • It is possible to use reflection to create much of the code in the decorator
Using Reflection to Create the Source for a Decorator
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javaexamples/decorator/DecoratorMaker.java
 
There's Always More to Learn
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