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

[Alexey Saenko]

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.

[Jaikiran Pai]

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.

[Alexey Saenko]

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?

[Jaikiran Pai]

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.

[Durai Kalairajan]

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

[Joe Harry]

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

[Jaikiran Pai]

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.