better than id based identity and could you provide examples of why?


many thanks


Andrew

Please start reading the documentation and this page: http://www.hibernate.org/109.html

I have read the article you pointed me to. My problem is this, I have a parent class which can have any number of associated child items. The parent ID is used as a foreign key in the child class. How can I acheive the same thing by implementing a 'a good equals() method'?? - (www.hibernate.org/109.html - Seperating object id and business key).

My maps are as follows:

[b]Order.htm.xml[b/]

<hibernate-mapping package="test">
<class name="Order" table="orderstbl">
<id name="ID" column="order_id" type="string" unsaved-value="null">
<generator class="uuid.hex"/>
</id>
<property name="OrderDate" column="order_date" type="timestamp" not-null="true"/>
<property name="PriceTotal" column="price_total" type="double" not-null="true"/>
<property name="UserID" column="user_id" type="integer" not-null="true"/>
<set name="OrderItems" table="orderitemstbl" inverse="true" cascade="all">
<key column="order_id"/>
<one-to-many class="OrderItem"/>
</set>
</class>
</hibernate-mapping>

[b]OrderItems.hbm.xml[b/]

<hibernate-mapping package="test">
<class name="OrderItem" table="orderitemstbl">
<id name="ID" column="orderitem_id" type="string" unsaved-value="null">
<generator class="uuid.hex"/>
</id>
<property name="OrderID" column="order_id" type="string" not-null="true" insert="false" update="false"/>
<property name="StockID" column="stock_id" type="string" not-null="true" insert="false" update="false"/>
<property name="Amount" column="amount" type="integer"/>
<property name="Price" column="price" type="double"/>
<many-to-one name="Order" class="Order" column="order_id" />
<many-to-one name="Stock" class="Stock" column="stock_id"/>
</class>
</hibernate-mapping>

many thanks in advance


Andrew

please point me in the right direction where I can see code which shows me how to amend my maps so that I can take advantage of equal(). As shown in my maps, i have specified a parent class which has a one-to-many association with a child class. At the moment the id's for each class are being generated and only being made available after being saved session.save(), where as i wish to be able to associate different child items to a parent before saving the parent. I already have a set specified in my parent map:

<class name="Order" table="orderstbl">
<id name="ID" column="order_id" type="string" unsaved-value="null">
<generator class="uuid.hex"/>
</id>
<property name="OrderDate" column="order_date" type="timestamp" not-null="true"/>
<property name="PriceTotal" column="price_total" type="double" not-null="true"/>
<property name="UserID" column="user_id" type="integer" not-null="true"/>

<set name="OrderItems" table="orderitemstbl" inverse="true" cascade="all">
<key column="order_id"/>
<one-to-many class="OrderItem"/>
</set>
</class>

To take advantage of equal() can i use the following?:

<set name="OrderItems" table="orderitemstbl" inverse="true" cascade="all">
<key column="order_id"/>
<property name="OrderDate" column="order_date" type="timestamp" not-null="true"/>
<property name="UserID" column="user_id" type="integer" not-null="true"/>
<one-to-many class="OrderItem"/>
</set>

What about the id line, do i remove that? so my parent map now looks like:

<class name="Order" table="orderstbl">


<property name="PriceTotal" column="price_total" type="double" not-null="true"/>

<set name="OrderItems" table="orderitemstbl" inverse="true" cascade="all">
<key column="order_id"/>
<property name="OrderDate" column="order_date" type="timestamp" not-null="true"/>
<property name="UserID" column="user_id" type="integer" not-null="true"/>
<one-to-many class="OrderItem"/>
</set>
</class>

Could someone please please point me in the right direction here as I deadline that is very quickly running away from me here!


many thanks in advance


Andrew

We need to start spreading the wealth around here! I have read the article http://www.hibernate.org/109.html which tells me what one should do in terms of you [b]'using a set of properties for equals() that identify your individual objects'[b/], what I would like to know now is how to apply that in the real world terms. As i have said before I have a one to many association on a parent/child relationship, the parent id being used as a foreign key in the child. My first port of call is to know how to amend my maps to reflect this, my second being the code i would use to update/delete from the parent/child association?

if someone could point me in the right direction I would be most greatfull.


many thanks again

Andrew

Man, its sunday, have some patience. This is a "spare time help" forum, not a commercial support tool were everyone jumps on your questions immediately.

and if I had anymore hair to pull out, trust me I would! As I have no more hair to pull out, I can now only be but patient ;-)


regards


Andrew

why don't you just do as the 109.html pages eplain ?
Add a equals method which uses the best natural key....(remember if you dont have a unique natural key THEN == is probably the best candidate, right ? (think about it))

first of all i am new to this game.. so I am a bit like a man fumbling in the dark.. and what I am fumbling for at the moment is syntax examples. I would like to see examples of how to define my maps for starters and then the corresponding hibernate code to take advantage of the maps, do you have or could you point my in the direction of any examples please.


many thanks


Andrew

Get the Hibernate in Action ebook if the examples on the website and documentation are not enough.

There are a tons of examples at the hibernate.org site under documentation / and as christian says, if that is not enough then get the book.

But besides that go look in the unit test cases or maybe even try to make middlegen generate hbm.xml for you if you have an existing db....it will make a best first shot mapping for you.

if you have hbm.xml then you could try using hbm2java to generate matching java code....

all for the help you have given me on this issue, I will purchase Hibernate in Action book as you mention.


many regards


Andrew