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From Craig L Russell <Craig.Russ...@Sun.COM>
Subject Re: Persistent properties for classes
Date Fri, 16 Mar 2007 05:23:19 GMT
Hi Bin,

Thanks for taking time to reply.

My question is whether we should permit both a persistent field and a  
persistent property to have the same name. I think that the answer is  
no. I'm not sure if this is also your position.

In your example, referring to "${user.name}", should you get the  
value of the field called name, or get the result of getName()? I  
believe that the specification of EL requires a property, i.e. getName 
().

And in JDOQL, if you have a persistent property called name, then  
name == "Mike" gives you the right result.

It's really up to the user whether to use persistent properties or  
persistent fields. Your examples can work with either properties or  
fields, but the results are ambiguous if you have both persistent  
field "name" and persistent property "name".

Craig

On Mar 15, 2007, at 7:55 PM, Bin Sun wrote:

> Hi!
>
>     I strongly oppose to using a different field name
> for a property.
>
>     For a webapp, we may use a JDO javabean like this:
> "${user.name}", and we also frequently need to do
> JDOQL like this: "name=='Mike'".  Keeping field names
> the same as property names can reduce much confusion
> for coders. This is a basic rule for my development.
>
>     How do others think?
>
>
> --- Erik Bengtson <erik@jpox.org> wrote:
>
>> Hi,
>>
>> We are implementing persistent properties, and I
>> have some questions.
>>
>> Question 1:
>> ------------------
>> Take this example:
>>
>> <class name="Person">
>> <field name="name"/>
>> <property name="birth"/>
>> </class>
>>
>> class Person
>> {
>>    String name;
>>    String _birth;
>>
>>    public Date getBirth()
>>    {
>>       return this._birth;
>>    }
>>
>>    public void setBirth(Date birth)
>>    {
>>       this._birth = birth;
>>    }
>> }
>>
>> Is it allowed to have mixed persistent fields and
>> persistent properties in same
>> Class or Super Classes?
>>
>> In JPA, this is explicitly unspecified.
>>
>> IMO it should not be allowed to avoid user errors
>> (possibly overriding values or
>> persisting twice the same information).
>>
>> Question 2:
>> ------------------
>> Take this example:
>>
>> <class name="Person">
>> <property name="name"/>
>> <property name="birth"/>
>> </class>
>>
>> class Person
>> {
>>    String _name;
>>    String _birth;
>>
>>    public String getName()
>>    {
>>       return this._name;
>>    }
>>
>>    public void setString(String name)
>>    {
>>       this._name = name;
>>    }
>>    public Date getBirth()
>>    {
>>       return this._birth;
>>    }
>>
>>    public void setBirth(Date birth)
>>    {
>>       this._birth = birth;
>>    }
>> }
>>
>> By default, _name and _birth would have persistence
>> modifier = persistent. In
>> this case we are using persistent properties, does
>> the default persistence
>> modifier for fields changes to transient?
>>
>> Question 3:
>> ------------------
>> Take this example:
>>
>> <class name="Person">
>> <property name="name"/>
>> <property name="birth"/>
>> </class>
>>
>> class Person
>> {
>>    String _name;
>>    String _birth;
>>
>>    public String getName()
>>    {
>>       return this._name;
>>    }
>>
>>    public void setString(String name)
>>    {
>>       this._name = name;
>>    }
>>    public Date getBirth()
>>    {
>>       throw new UnbornException();
>>    }
>>
>>    public void setBirth(Date birth)
>>    {
>>       this._birth = birth;
>>    }
>> }
>>
>> If an exception is raised from the getter/setter,
>> what should be done by the
>> implementation?
>>
>> In JPA, there is an automatic rollback.
>>
>> Regards,
>>
>> Erik Bengtson
>>
>
>
>
>
> ______________________________________________________________________ 
> ______________
> Don't pick lemons.
> See all the new 2007 cars at Yahoo! Autos.
> http://autos.yahoo.com/new_cars.html

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!


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