A Novel Implementation of Observer Pattern by Aspect Based on Java Annotation

摘要

In the implementation of Observer pattern by OOP, the subject objects and the observer objects must implement an interface or extend an abstract class to indicate their roles. When the pattern is implemented by AOP, there is not such a requirement. The participants and their relations are defined in an aspect, it isn't necessary for these participants to implement an interface or extending an abstract class. But users are required to know an aspect language to use this method. This paper provides a novel method to implement this pattern; participant objects and their relations are defined by Java annotations. On the basis of analyzing Observer pattern implemented by AOP, the paper discusses bow to define annotations to annotate participant classes and define their relations, how to establish the association between the subject and the observer is discussed in details. After analyzing classes annotated, the aspect is generated, then compiling and weaving this aspect with the target classes is done. So users may use Aspect implementation by Java annotation.