In Chapter 4 you did a very good job of explaining how to use JPA or custom annotations to augment mapping files to set access levels of fields and methods. What I am trying to understand is why one would do this and to what benefit. I believe I understand the implications pertaining to components but need to understand how this would affect persistence.

I'm not sure what else I could possibly write about this. Maybe read it again? :)

If a have a

class foo(
String id;
String name;




)


Is there a benefit to setting field access vs. method access? What I was getting from the book was the annotations controlled hibernate persistence calls foo.getID() vs. foo.Id at time of insert,etc. IF I did not do any additional logic in getters and setters (ie. make sure child and parent objects were set properly see your item and categories explanation) wouldn't it make sense to make all values field access. Or is that your point. Is there anything else happening "under the covers" to take into concideration? Thanks and sorry if this is a dumb question..

I really don't understand your question.

@Entity
public class Foo{
@Id @GeneratedValue
private Long id;
private String name;

public Long getId(){

}

public String getName(){


}


}


@Entity
pubic class Bar{
private Long id;
private String name

@Id @GeneratedValue
public Long getId(){

}

public String getName(){

}
}

In Foo all attributes of class will be accessed by Hibernate through Fields.
In Bar Attribute ID will be accessed by Hibernate(?) through getter. But in either case getters and setters exists. Italicized is from book that is the basis of my question. What is benefit/trade-off of one method vs. the other?

Uhm, that you don't need to have the getters and/or setter if you have field access? I mean, it's up to you what you want.

Ok that is why I made 2 classes both having getters and setters did not know if it affected HIBERNATE generated code.

Hibernate uses Java reflection, it does not care whether you configure it for field or getter access.

As I know there is a slight difference in efficiency.
For method access Hibernate uses the CGLIB code generation library to generate higly efficient code to access the bean with getter/setter methods.
For field access Hibernate uses reflection to access the field directly what is slighlty slower than using the generated code.


Greetings,
Robert

This is only true for JDK 1.3, AFAI remember. We already discussed removing the CGLIB reflection optimizier in a future version, because it has no real effect on JDK 1.4 and 5.0.

not remove, but we did disable it per default in 3.2 and onwards.