The difference between field-based access and property-based access

Hi guys,

There is written:

EJB3 in Action wrote:Defining O/R mapping using fields or instance variables of entity is known as field-based access, and using O/R mapping with properties is known as property-based access.

I have some doubts about the following questions:
What do the authors mean under "field-based access" and "property-based access"? What are fields and properties? and what is the difference between them?

Thanks a lot in advance,
Alex.

Alexey Saenko wrote:
I have some doubts about the following questions:
What do the authors mean under "field-based access" and "property-based access"? What are fields and properties? and what is the difference between them?

Field based access uses the member variables whereas property based access uses getter/setters.

In other words, in terms of practice in the case of field-based access a developer annotates instance variables and in the case of property-based he (or she) annotates getters/setters, right? Is there really so big difference between such styles to annotate? It looks like these styles are completely identical. Am I wrong?

Alexey Saenko wrote:In other words, in terms of practice in the case of field-based access a developer annotates instance variables and in the case of property-based he (or she) annotates getters/setters, right?

That's correct.

Alexey Saenko wrote:
Is there really so big difference between such styles to annotate? It looks like these styles are completely identical. Am I wrong?

It's more of a personal choice. But the important thing is, you can't mix and match those 2 styles. i.e. your entity should not be annotated at field level as well as property level.

Jaikiran Pai wrote:

Alexey Saenko wrote:In other words, in terms of practice in the case of field-based access a developer annotates instance variables and in the case of property-based he (or she) annotates getters/setters, right?

That's not correct.Only getters can be annotated.

JPA specification says,
2.1.1 Persistent Fields and Properties
When property-based access is used, the object/relational mapping annotations for the entity class
annotate the getter property accessors

There's nothing wrong when you annotate the setter, but it will be silently ignored by the container.

Durai Kalairajan wrote:

Jaikiran Pai wrote:

Alexey Saenko wrote:In other words, in terms of practice in the case of field-based access a developer annotates instance variables and in the case of property-based he (or she) annotates getters/setters, right?

That's not correct.Only getters can be annotated.

Durai, you are right. I did not choose the exact term while explaining that. For property based access, annotating setters will not help.