Author: danhaywood
Date: Fri Apr 26 06:24:11 2013
New Revision: 1476061
URL: http://svn.apache.org/r1476061
Log:
isis site - updating info on jdo workarounds
Modified:
isis/site/trunk/content/components/objectstores/jdo/workarounds.md
Modified: isis/site/trunk/content/components/objectstores/jdo/workarounds.md
URL:
http://svn.apache.org/viewvc/isis/site/trunk/content/components/objectstores/jdo/workarounds.md?rev=1476061&r1=1476060&r2=1476061&view=diff
==============================================================================
--- isis/site/trunk/content/components/objectstores/jdo/workarounds.md
(original)
+++ isis/site/trunk/content/components/objectstores/jdo/workarounds.md Fri Apr
26 06:24:11 2013
@@ -4,6 +4,8 @@ There are a number of limitations in Dat
* loading the children from the parent does not fire the `jdoPostLoad`
callback (either on the entity via `javax.jdo.listener.LoadCallback` nor
`javax.jdo.listener.LoadLifecycleListener`)
+ More precisely, this doesn't occur if the child being loaded has subclasses,
and the subclasses has fields/properties that are part of the default fetch
group.
+
* persisting a child entity does not cause the parent's collection to be
updated.
Note that this is documented behaviour; see this [DataNucleus
page](http://www.datanucleus.org/products/datanucleus/jdo/orm/relationships.html).
@@ -41,19 +43,29 @@ The service will then be automatically i
## Workaround for Lazy Loading
-In a bidir 1:m, we have found that the post-load callback for the children is
not fired.
+In a bidir 1:m, we have found that in certain circumstances the post-load
callback for the children is not fired. Specifically, if the child has
subclasses, and the subclass has fields/properties that are in the [default
fetch group](http://db.apache.org/jdo/fetchgroups.html).
+
+A test case illustrating the problem (*though whether with the spec or the DN
implementation, we are not yet sure*) can be found [here on
github](https://github.com/danhaywood/test-jdo).
The consequence of this is that any domain services used by the child object
(including `DomainObjectContainer`) are not injected into the child.
The workaround is to have the parent inject the services when returning the
children.
-For example, suppose we have a Customer <->* Order bidir relationship. In
Customer, we would have:
+For example, suppose we have a `Customer` <->* `Order` bidir relationship, and
where `Order` my have subclasses, eg `RushedOrder`. In `Customer`, we would
add a new method `getOrdersWorkaround()`:
// {{ Orders (Collection)
private SortedSet<Order> orders = new TreeSet<Order>();
@Persistent(mappedBy = "customer")
public SortedSet<Order> getOrders() {
+ return this.orders;
+ }
+
+ public void setOrders(final SortedSet<Order> orders) {
+ this.orders = orders;
+ }
+
+ public SortedSet<Order> getOrdersWorkaround() {
if (this.orders == null) {
// this can happen, it would seem, by JDO/DN when it is
@@ -63,7 +75,7 @@ For example, suppose we have a Customer
// inject each element before returning it
return Sets.newTreeSet(
Iterables.transform(
- this.orders,
+ this.getOrders(),
new Function<Order, Order>(){
public Order apply(Order order) {
return isisJdoSupport.injected(order);
@@ -72,10 +84,6 @@ For example, suppose we have a Customer
}
}
- public void setOrders(final SortedSet<Order> orders) {
- this.orders = orders;
- }
-
Alternatively, you can reload each child object. Change:
new Function<Order, Order>(){
