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does java annotations uses the java refection.

 
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I have read that java reflection is working behind the scene of annotations.
Q1) is it true?
Q2) how does reflection help to make annotations useful?
 
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Howdy, Nuwan!

I have read that java reflection is working behind the scene of annotations.
Q1) is it true?
Q2) how does reflection help to make annotations useful?



Q1: Well, depends on what you mean by "working behind the scene of annotations". An annotation is simply a form of metadata.
Q2: An annotation does not do anything alone. It can't contain code, which means that it needs other code to consume it. This is done with reflection. Here's an example:



Now, in order to verify if an annotation annotates one element of your class (the doStuff() method in the example above), you can use reflection:



Most of the metadata-based frameworks nowadays use annotations. Spring, EJB, JPA, Hibernate Validator are examples of such frameworks.
 
Nuwan Arambage
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Hi Roberto,

I think i got your point.please correct me if i'm wrong.okey for a example, in JPA we can use @Entity to annotate classes as entities.when I apply what you said is to my example,JPA reference implementation uses java reflection to map the annotated class into database table.Am I right?.

Hope you reply.I need to clear my doubts becase I use annotations without knowing what you said early.

Thnaks & regards,

Nuwan Aramabge


 
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Yes. JPA, Struts, JSF (...) all of those guys use reflection to search for @annotations.
 
Nuwan Arambage
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Hebert Coelho wrote:Yes. JPA, Struts, JSF (...) all of those guys use reflection to search for @annotations.



yes, thanks you again for clearing the doubts.......
 
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