For this blog I chose an article on DZone which is basically an online community for software development. I discovered them through the UML exercise in class because of their “refcard” we used as a guide. For the article, I went with “Decorator Pattern Tutorial with Java Examples” because I wanted to learn a design pattern I’d never heard of. Also, with Java examples it would be easiest to follow along for me.
To get started, it’s important to know that the decorator pattern allows class behavior to be extended dynamically at run-time. This means attributes can be added to Objects dynamically which the author relates to the concept of a wrapper object. The decorator pattern is more broadly considered a structural pattern which encompasses many different patterns that focus on identifying a simple way of implementing relationships between entities.
One of the principles of the decorator design is that classes should be open for extension but closed for modification. Two main instances which the decorator pattern is useful are 1) when object behavior should be dynamically modifiable or 2) when concrete implementations should not be coupled to behavior. While sub classing can achieve the same effect, decorator can decrease maintenance by preventing too much sub classing. The author suggests to only use the open/closed principle where code is least likely to change to avoid making the code too abstract and complex.
A good example of the decorator pattern would be a company’s email system. If an email is generated and sent out from a company employee the decorator pattern could account for different scenarios. If the email is sent internally nothing occurs, but if the email is sent externally the system could “decorate” the email with a copyright or confidential statement attached to it.
After reading about the decorator pattern I can see the benefits but I don’ t think I have come across a project thus far that I would have really been able to put this to use. After a quick google search it looks like Java’s I/O streams implementation is a good example for learning more about the decorator pattern. I will probably look more into this as I can’t see how this article really helped me much moving forward. I think after I play around with it I’ll be able to better understand how I could apply it to my own projects. This article was good for a general explanation but not for learning the actual implementation.
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