JcrModifiablePropertyMap works by storing all changes in an internal
cache. Upon save() the cached changes are written to the
javax.jcr.Node, and the node is save()d.
This makes sequences such as this impossible:
try {
// Modify a property through PersistableValueMap
PersistableValueMap props = resource.adaptTo(PersistableValueMap.class);
props.put("prop", value);
props.save();
// Do some other, unrelated changes
Node sibling = resource.adaptTo(Node.class).getParent().addNode("child");
sibling.doSomeChange(); // This may throw an exception
session.save();
} catch(Exception e) {
session.refresh(false); // Cancel the pending changes of this session
}
The idea is to save all changes to the repository in one single
session.save(). If anything fails, the session is reverted.
This doesn't work because the properties of PersistableValueMap is not
written to the node until PersistableValueMap.save(), and by then, it
is too late to revert the session, as the changes of
PersistableValueMap are already persisted.
We could make such operations easier by introducing a new method
PersistableValueMap.write() (in lack of a better name).
In case of JcrModifiablePropertyMap, most of save() would be moved to
write(), leaving out node.save().
So that JcrModifiablePropertyMap.save() would be:
public void save() throws PersistenceException {
this.write();
node.save();
}
In the code example above, replacing props.save() with props.write()
should give the desired functionality.
WDYT?
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