Thank you.
I was wondering why the List members were not cloned and just noticed
the clone method was called on the List, not the members.
Also I added one more test, but I don't understand why it succeeds:
assert clonedEvent.subEvents.first().event.is(clonedEvent)
Obviously the nested event is a shallow copy of the clonedEvent. That's
really nice, although I expected a copy of the original event here.
With regard to the ToString-Annotation and mutual recursion, I think a
representation similar to those by the InvokerHelper methods seem to fit
for data structures only (trees, lists, maps).
In the Event/SubEvent example I'd like to know/see that SubEvents have
an event which reference the parent Event. However, the former is a good
start to avoid stackoverflows in the first place.
Regards
Nikolai
Am 06.02.19 um 02:38 schrieb Paul King:
Hi,
With regard to stack overflow when printing. This is a known
limitation. ToString has been made smart enough to handle self
references, e.g.
import groovy.transform.*
@ToString
class Tree {
Tree left, right
}
def t1 = new Tree()
t1.left = t1
println t1 // => Tree((this), null)
but isn't smart enough to handle mutual recursion, e.g.:
def t2 = new Tree()
t1.left = t2
t2.left = t1
println t1 // => StackOverflowError
The plan has always been to make it smarter but we haven't done it
yet. PRs welcome.
If anyone is interested, I'd recommend something simple like what we
have done for lists and maps in the respective InvokerHelper methods.
E.g. for maps, self reference is already handled:
def t3 = [:]
t3.with{ left = t3; right = t3 }
println t3 // => [left:(this Map), right:(this Map)]
And mutual reference is handled by setting a maximum size (30 in the
example below and three dots is used once the toString becomes greater
than 30 in size):
import org.codehaus.groovy.runtime.InvokerHelper
def t4 = [left: t3]
t3.right = t4
println InvokerHelper.toMapString(t3, 30) // => [left:(this Map),
right:[left:[...]]]
It works so long as the Map contents themselves don't have stack
overflow scenarios that aren't catered for (some scenarios are handled).
Similarly for lists, self reference is handled:
def items = []
3.times{ items << items }
println items // [(this Collection), (this Collection), (this
Collection)]
but you can limit the size (e.g. for the case above) or to handle
mutual reference:
println InvokerHelper.toListString(items, 30) // => [(this
Collection), (this Collection), ...]
def list1 = []
def list2 = []
list1 << list2
list2 << list1
//println list1 // StackOverflowError
println InvokerHelper.toListString(list1, 10) // =>
[[[[[[[[[[[...]]]]]]]]]]]
So getting back to @ToString, I'd imagine an enhancement could involve
either generating a toString(int maxSize) method or supporting a
maxSize annotation attribute that was automatically supported in the
generated code for the normal toString method.
With regard to the AutoClone issues, as per the documentation, the
supported cloning styles have various assumptions, e.g. SIMPLE style
assumes child classes are of a similar style (or have equivalent
methods), and the basic styles support only shallow cloning. For your
case you want deep cloning, so SERIALIZATION would be the way to go.
abstract class AbstractEvent {
Date created
String createdBy
Date modified
String modifiedBy
}
@AutoClone(style=SERIALIZATION)
@ToString(includeSuper = true)
class Event extends AbstractEvent implements Serializable {
Long id
String someText
ArrayList<SubEvent> subEvents = new ArrayList()
}
@AutoClone(style=CLONE)
@ToString(includeSuper = true, excludes = ['event'])
class SubEvent extends AbstractEvent implements Serializable {
Long id
String someText
Event event
}
Cheers, Paul.
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On Wed, Feb 6, 2019 at 7:46 AM Nikolai (gmail)
<nikolai.du...@googlemail.com <mailto:nikolai.du...@googlemail.com>>
wrote:
Hello,
I experienced some Issues using ToString and AutoClone on Entities
(Spring JPA).
Both can lead to endless loops / a stackoverflow, when classes
reference each other.
While it's fine for AutoClone, I think the generated
toString-Method should recognize it was already called once and
return a dummy value or just the object reference.
Anyway, I got bigger issues using AutoClone:
1. I use an abstract class to add auditing columns to all my
tables. All my Entities inherit from that class (AbstractEvent in
this example). Since these fields should be empty/null on cloning,
I'd like to omit the AutoClone annotation on that class. But this
leads to an error: No signature of method:
Event.cloneOrCopyMembers() is applicable for argument types:
(Event) values: [Event(null, null, [], Event@54d9d12d)].
2. SubEvent objects within Event.subEvents were not cloned.
import groovy.transform.AutoClone
import groovy.transform.Canonical
import groovy.transform.ToString
import static groovy.transform.AutoCloneStyle.SIMPLE
@AutoClone(style=SIMPLE) //1. error when you remove this
abstract class AbstractEvent {
Date created
String createdBy
Date modified
String modifiedBy
}
@AutoClone(style=SIMPLE)
@ToString(includeSuper = true)
class Event extends AbstractEvent {
Long id
String someText
ArrayList<SubEvent> subEvents = new ArrayList();
}
@AutoClone(style=SIMPLE)
@ToString(includeSuper = true, excludes = ['event'])
class SubEvent extends AbstractEvent {
Long id
String someText
Event event;
}
public static void main(String[] args){
Event event = new Event(
id: 1,
someText: "Event 1",
created: new Date(),
createdBy: "me");
SubEvent subEvent1 = new SubEvent(
id: 1,
someText: "SubEvent 1",
event: event);
event.subEvents += subEvent1
Event clonedEvent = event.clone()
assert !event.is <http://event.is>(clonedEvent)
assert !event.subEvents.is
<http://event.subEvents.is>(clonedEvent.subEvents)
assert
!event.subEvents.first().is(clonedEvent.subEvents.first()) // 2. fails
}
Hope, you can help me here.
Kind Regards
Nikolai
