Question about optionality in one-to-one relationships
Hi, Can someone help me understand something? I’m trying to model a one-to-one relationship between two entities but I can’t seem to get the relationship to be optional. In my specific case I need to model an entity representing shipments with a postal service. Each shipment needs to have a number taken from a range/group that is pre-assigned by the postal service. Thus I created a SHIPMENT_NUMBER entity with just an INTEGER attribute and then used that attribute to build the relationship with the SHIPMENT entity. Possibly with “To dep PK” as well. I want the relationship to be optional so that I can generate SHIPMENT_NUMBER as many as I want and populate them with the numbers assigned by the postal service and only later, when the real SHIPMENT is actually needed/created, link it with the number in a one-to-one fashion. I’m not sure why, but my class generated content always shows the relationship as mandatory. Coming from the WebObjects world, I'm used to a modeler that explicitly shows checkboxes for isMandatory on relationships like with the attributes. Here in Cayenne it seems that optionality is implicitly determined based on the design. Have I misunderstood something? Is my design flawed? Any tip is appreciated. Regards, Riccardo
Re: Question about optionality in one-to-one relationships
Hi Riccardo, I may have completely misunderstood your intention, but here is my first cut for a model: cayenne-o2o.xml: http://cayenne.apache.org/schema/10/domain"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:schemaLocation="http://cayenne.apache.org/schema/10/domain https://cayenne.apache.org/schema/10/domain.xsd"; project-version="10"> datamap.map.xml: http://cayenne.apache.org/schema/10/modelMap"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:schemaLocation="http://cayenne.apache.org/schema/10/modelMap https://cayenne.apache.org/schema/10/modelMap.xsd"; project-version="10"> http://cayenne.apache.org/schema/10/info"; name= "comment" value="This ID is the same as SHIPMENT's ID."/> http://cayenne.apache.org/schema/10/info"; name= "comment" value="This is the shipment number."/> Copy/Paste these files somewhere, then try loading them up into your 4.2 Modeler and see if it is close. mrg On Tue, Jan 9, 2024 at 9:54 AM Riccardo De Menna wrote: > Hi, > > Can someone help me understand something? > > I’m trying to model a one-to-one relationship between two entities but I > can’t seem to get the relationship to be optional. > > In my specific case I need to model an entity representing shipments with > a postal service. Each shipment needs to have a number taken from a > range/group that is pre-assigned by the postal service. > > Thus I created a SHIPMENT_NUMBER entity with just an INTEGER attribute and > then used that attribute to build the relationship with the SHIPMENT > entity. Possibly with “To dep PK” as well. > > I want the relationship to be optional so that I can generate > SHIPMENT_NUMBER as many as I want and populate them with the numbers > assigned by the postal service and only later, when the real SHIPMENT is > actually needed/created, link it with the number in a one-to-one fashion. > > I’m not sure why, but my class generated content always shows the > relationship as mandatory. > > Coming from the WebObjects world, I'm used to a modeler that explicitly > shows checkboxes for isMandatory on relationships like with the attributes. > Here in Cayenne it seems that optionality is implicitly determined based on > the design. > > Have I misunderstood something? Is my design flawed? > > Any tip is appreciated. > > Regards, > Riccardo
Re: Question about optionality in one-to-one relationships
Hi Michael,
Thank you for helping. Yes… you modeled exactly what I described down to the
delete rules. I imported your files in modeler and run class generation but I
still get the relationship (TO_SHIP in your model) to appear as mandatory.
Could it be an issue in class generation?
This is a little VE snippet I use in my template to output a static list of
mandatory relationships.
#foreach( $rel in ${object.DeclaredRelationships} )
#if (${rel.isMandatory()} && !${rel.ToMany} )
#set($bar =
$requiredRelationships.add("${stringUtils.capitalizedAsConstant($rel.Name)}_PROPERTY"))
#end
#end
public static final List REQUIRED_RELATIONSHIPS = List.of(
#foreach( $rel in ${requiredRelationships} )
${rel}#if(!$foreach.last),#end
#end
);
And contrary to what I would expect, I get this in my superclass:
public static final List REQUIRED_RELATIONSHIPS = List.of(
TO_SHIP_PROPERTY
);
Riccardo De Menna
> On 10 Jan 2024, at 01:20, Michael Gentry wrote:
>
> Hi Riccardo,
>
> I may have completely misunderstood your intention, but here is my first
> cut for a model:
>
> cayenne-o2o.xml:
>
> http://cayenne.apache.org/schema/10/domain";
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
> xsi:schemaLocation="http://cayenne.apache.org/schema/10/domain
> https://cayenne.apache.org/schema/10/domain.xsd";
> project-version="10">
>
>
>
> datamap.map.xml:
>
> http://cayenne.apache.org/schema/10/modelMap";
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
> xsi:schemaLocation="http://cayenne.apache.org/schema/10/modelMap
> https://cayenne.apache.org/schema/10/modelMap.xsd";
> project-version="10">
>
>
>
> />
>
>
> >
> http://cayenne.apache.org/schema/10/info"; name=
> "comment" value="This ID is the same as SHIPMENT's ID."/>
>
>
> http://cayenne.apache.org/schema/10/info"; name=
> "comment" value="This is the shipment number."/>
>
>
> "optimistic" dbEntityName="SHIPMENT"/>
> lock-type="optimistic" dbEntityName="SHIPMENT_NUMBER">
>
>
> >
>
>
> toDependentPK="true">
>
>
> deleteRule="Cascade" db-relationship-path="toShipNum"/>
> deleteRule="Deny" db-relationship-path="toShip"/>
>
>
> Copy/Paste these files somewhere, then try loading them up into your 4.2
> Modeler and see if it is close.
>
> mrg
>
>
> On Tue, Jan 9, 2024 at 9:54 AM Riccardo De Menna wrote:
>
>> Hi,
>>
>> Can someone help me understand something?
>>
>> I’m trying to model a one-to-one relationship between two entities but I
>> can’t seem to get the relationship to be optional.
>>
>> In my specific case I need to model an entity representing shipments with
>> a postal service. Each shipment needs to have a number taken from a
>> range/group that is pre-assigned by the postal service.
>>
>> Thus I created a SHIPMENT_NUMBER entity with just an INTEGER attribute and
>> then used that attribute to build the relationship with the SHIPMENT
>> entity. Possibly with “To dep PK” as well.
>>
>> I want the relationship to be optional so that I can generate
>> SHIPMENT_NUMBER as many as I want and populate them with the numbers
>> assigned by the postal service and only later, when the real SHIPMENT is
>> actually needed/created, link it with the number in a one-to-one fashion.
>>
>> I’m not sure why, but my class generated content always shows the
>> relationship as mandatory.
>>
>> Coming from the WebObjects world, I'm used to a modeler that explicitly
>> shows checkboxes for isMandatory on relationships like with the attributes.
>> Here in Cayenne it seems that optionality is implicitly determined based on
>> the design.
>>
>> Have I misunderstood something? Is my design flawed?
>>
>> Any tip is appreciated.
>>
>> Regards,
>> Riccardo
