Re: Persistent properties for classes

[Craig L Russell]

Hi Erik,

We should be able to discuss this at Friday's conference call.

On Mar 14, 2007, at 2:47 AM, Erik Bengtson 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;
   }
}


Class or Super Classes?

In JPA, this is explicitly unspecified.

Is it allowed to have mixed persistent fields and persistent properties in same

Well, not really. From 2.1.1, .A single access type (field or property access) applies to an entity hierarchy.

persisting twice the same information).

IMO it should not be allowed to avoid user errors (possibly overriding values or

But I don't see the issue with allowing implicit field persistence (since JDO 1.0) or explicit property persistence.

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;
   }
}


modifier for fields changes to transient?

By default, _name and _birth would have persistence modifier = persistent. In this case we are using persistent properties, does the default persistence

Yes. Field names must not be the same as property names. If a property is explicitly declared to be persistent, the corresponding field must not be persistent. There are rules for determining whether fields are persistent; see 18.15 for default persistence-modifier for fields. There is no such treatment for properties.

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;
   }
}


implementation?

In JPA, there is an automatic rollback.

If an exception is raised from the getter/setter, what should be done by the

Craig

I guess this is not specified in JDO. I'd like to see this generate a StupidUserException but not set the RollbackRequired flag. Not every exception should cause a rollback.

Regards,

Erik Bengtson

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

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