How do Annotations works internally in Java or any other programming language?

Question

I having hard time understanding importance and benefits of Annotations and so have two questions regarding them:

1. What are the benefits of Annotations as compared to XML Configuration?
2. How do Annotations work internally?
3. Is it fair enough to say that annotation binds application tightly whereas with XML Configuration Application is loosely coupled?

Would appreciate pros and cons comparison with XML Configuration with example so that it would be much more helpful for me to understand.

Regards.

Answer 1

For your 1st question,

• Xml configuration versus Annotation based configuration

Personally, I feel, there are two criteria's

1. Can annotations simplify the metadata ?

   If annotations do not reduce the amount of metadata that you have to provide (in most cases they do), then you shouldn’t use annotation.

2. Can changes to the metadata break behavior in your application?

   If not, then you can feel comfortable applying the change while the system is running in production. External config files are the best place for the metadata in this case because you don’t want to have to recompile your code to make the change.

For your 2nd question,

• How Do Annotations Work?

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Important Links :

• What are annotations and how do they actually work for frameworks like Spring?