Thanks Bill
I have experience with hibernate thats why i thought it could be
possible.
On Thu, Jun 3, 2010 at 12:00 AM, Bill Milligan <[email protected]>wrote:
>
> I believe you're going to have to change this to
>
> class User {
> String name;
> List <String> workNames; // or List <Long> workIds;
> }
>
> class Work {
> String name;
> String userName; // or Long userId;
> }
>
> This is actually you'd design this under the MDA paradigm, actually. You
> need to be able to change each independently of the other. As far as
> "automatic population", like an ORM would do, I don't think this is
> possible. You'll have to do this manually. Honestly, you won't lose much
> by doing two queries.
>
> On Wed, Jun 2, 2010 at 2:12 PM, RAVINDER MAAN <[email protected]> wrote:
>
>> Thank you so much for your answer Bill
>> yes you are rite the way i wrote its many to many relation.Actually I
>> want relation as below
>>
>> class User{
>> Long id;
>> String username;
>> List<Work> workList;
>> }
>>
>> class Work{
>> Long id;
>> String workname;
>> String username;
>>
>> }
>> you can see work class has username and user class too has username.In
>> both classes primary key is id. I just want to know is there any way to get
>> workList populated automatically on retrieval of user object.we can do it
>> with 2 queries easily.we can reteriev user first then we can retrieve work
>> object with second query.
>>
>>
>> On Wed, Jun 2, 2010 at 10:35 PM, Bill Milligan
>> <[email protected]>wrote:
>>
>>>
>>> Are you trying one-to-many or many-to-many? By using a third table it
>>> sounds like you're trying to do many-to-many, not one-to-many.
>>>
>>> As best I can determine, the only real way to do this in GAE is to have a
>>> User class with a collection of string properties, containing the list of
>>> all Work ids. In this case a bidirectional link would be probably quite
>>> useful, so that a Work could be identified by its User id.
>>>
>>> Here's a scenario: Retrieve User by user id. Then, retrieve all Works
>>> in the list of work ids owned by the User.
>>>
>>> Note that this is not true object composition, with a User containing a
>>> List of Collection, but rather an indirect reference. This pattern is
>>> useful in a lot of circumstances where you want to be able to break up your
>>> object model into more modular deployable applications. On the other hand,
>>> I'd hate to be completely boxed in by this restriction.
>>>
>>> I'm just getting started with GAE so I'm very much not an expert. I'd
>>> love to know anybody else's thoughts on the matter.
>>>
>>> On Wed, Jun 2, 2010 at 12:10 AM, RAVINDER MAAN <[email protected]>wrote:
>>>
>>>> Hello all
>>>> can anybody please tell me how to implement simple one many
>>>> relation in java.I have user table and work table .Any user can do
>>>> many type of works.In user table i have userid but it is not primary
>>>> key of the user table.Then i have work table which has workid it is
>>>> also not primary key of the table.Normally in relation db we ca make
>>>> third table table which contains workid for every userid.What how can
>>>> we implement this thing appengine datastore.I want to have collection
>>>> all works in user object .can anybody please tell me how to define
>>>> this mapping?please note that in userid and workid are not primary
>>>> keys in both objects or tables.
>>>> Thanks in adavance.
>>>>
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>>>>
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>>
>>
>>
>> --
>> Regards,
>> Ravinder Singh Maan
>>
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>
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Regards,
Ravinder Singh Maan
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