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From Michael Gentry <>
Subject Re: Question on how to properly create parent-child nested dependent objects?
Date Wed, 20 Sep 2017 13:54:01 GMT
Hi Andrew,

I'm jumping in late here, but I did something very similar to what you are
trying to do with CommunicationType.find().  I create (auto-populate) a
reference table record based upon some enum values if missing, or just
return the reference table record if I find it.  I do this in a completely
separate (not a child) DataContext and copy the result into the main
destination context passed into the method.

This is from 3.1, so might vary a bit on the last line if you are on 4.x
(I'm using a deprecated method there and haven't updated yet):

    public static ContractDesignation fetch(ObjectContext
                                            ContractType       contractType,
        ContractDesignation contractDesignation = null;
        DataContext         dataContext         =
        Expression          exp1                =
ExpressionFactory.matchExp(CONTRACT_METHOD_PROPERTY, contractMethod);
        Expression          exp2                =
ExpressionFactory.matchExp(CONTRACT_TYPE_PROPERTY, contractType);
        Expression          exp3                =
ExpressionFactory.matchExp(FUNDING_VEHICLE_PROPERTY, fundingVehicle);
        Expression          exp                 =
        SelectQuery         query               = new
SelectQuery(ContractDesignation.class, exp);

        List<ContractDesignation> contractDesignations =

        // If no contract designation is found, create a new one, else use
        // one that was found (throwing an exception if too many are found).
        if (contractDesignations.isEmpty())
            contractDesignation =


        else if (contractDesignations.size() == 1)
            contractDesignation = contractDesignations.get(0);
            // There can be only one!
            throw new TooManyResultsException("There can be at most one
match for ContractDesignation contractMethod='" + contractMethod +
                                              "' / contractType='" +
contractType +
                                              "' / fundingVehicle='" +
fundingVehicle + "'");

        // Pull the fetched ContractDesignation into the destination
        return (ContractDesignation)

On Wed, Sep 20, 2017 at 9:16 AM, Andrew Willerding <
> wrote:

> I thought of this too but I'm trying to create the child object
> dynamically without having any impact on the parent object or making the
> coder of the parent object worry about creating child objects first.
> On 20/09/17 08:45 AM, Nikita Timofeev wrote:
>> Other option is to create CommunicationType first and then just use it:
>> CommunicationType type = CommunicationType.find("Email");
>> CommunicationLog cl = oc.newObject(CommunicationLog.class);
>> cl.setCommunicationDT(;
>> cl.setCommunicationType(type);
>> oc.commitChanges();
>> In this case everything will be in one context, and you can freely
>> commit CommunicationType to DB.
>> On Wed, Sep 20, 2017 at 3:37 PM, Mike Kienenberger <>
>> wrote:
>>> I haven't followed the details, so I don't know if using a separate
>>> object context is necessary, but all you need to do to move a data
>>> object (in your case "child") to a different context is to call
>>> parentContext.localObject(childDataObject) which will return
>>> childDataObjectInParentContext.   Note that this requires either a
>>> hollow or committed childDataObject as a modified (uncommitted) or new
>>> (uncommitted) data object's changes only exist in the
>>> childObjectContext.
>>> I may also have the syntax for localObject() wrong as I'm probably
>>> using an older version of Cayenne than you are.
>>> On Wed, Sep 20, 2017 at 8:30 AM, Andrew Willerding
>>> <> wrote:
>>>> I guess my issue is with how independent the commits can be.  Now that I
>>>> better understand this, my code example works as Nikita suggested (with
>>>> the
>>>> fix for my problem with the PrimaryKey table) and if I drop the commit
>>>> during the creation of the child object otherwise the commit during the
>>>> child creation will fail because the parent has not yet been assigned
>>>> with
>>>> the child object.
>>>> My objective is that I want the creation of the child to be completely
>>>> independent of the parent object for this situation. To do this I have
>>>> to
>>>> create a new ObjectContext  for the child object to make it independent
>>>> of
>>>> the parent's ObjectContext but when I return the newly created child
>>>> object
>>>> to the parent object I get the following
>>>> Caused by: org.apache.cayenne.CayenneRuntimeException: [v.4.0.B1 Jun
>>>> 02 2017
>>>> 15:11:18] Cannot set object as destination of relationship
>>>> communicationType
>>>> because it is in a different ObjectContext
>>>>      at
>>>> org.apache.cayenne.CayenneDataObject.willConnect(CayenneData
>>>>      at
>>>> org.apache.cayenne.CayenneDataObject.setToOneTarget(CayenneD
>>>>      at
>>>> etCommunicationType(
>>>>      at
>>>> com.callistacti.clientbase.Panel.PanelGroups.windowClose(Pan
>>>> So what I then needed to do is lookup the child object with the same
>>>> ObjectContext that the parent was using.
>>>> Out of curiousity, is there any simpler way of doing this?
>>>> On 19/09/17 09:16 AM, Aristedes Maniatis wrote:
>>>>> On 19/9/17 11:01PM, Andrew Willerding wrote:
>>>>>> The CommunicationType object does not yet exist permanently in the
>>>>>> database table so how or when does it generate the primary key for
>>>>>> object to be referenced by another object before it is committed?
>>>>>> was
>>>>>> hoping to not have to worry about this as a "high-level" user of
>>>>>> Cayenne.
>>>>> You are right, you don't need to worry about all that. Just create one
>>>>> context and save it at the end. Cayenne tracks the relationships
>>>>> between
>>>>> objects with a temporary key internally, but you don't need to think
>>>>> about
>>>>> that. Once Caynenne commits, everything is assigned proper primary
>>>>> keys and
>>>>> joined.
>>>>> Ari

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