[appengine-java] Re: JDO: Null parent on some children objects
ok, thanks.
The second answer is dictated by the fact that I don't want null
values to be returned from getter methods, otherwise I cannot safely
do an operation like:
mySecondObject.getTags().add(tag);
as I need to check if getTags() has returned null.
So, which is the best in your opinion between the two:
mySecondObject.getTags().add(tag1);
mySecondObject.getTags().add(tag2);
pm.makePersistent(mySecondObject);
AND
ListString tags = mySecondObject.getTags();
if (tags == null)
tags = neww ArrayListString();
tags.add(tag1);
tags.add(tag2);
mySecondObject.setTags(tags);
pm.makePersistent(mySecondObject);
For the owner... I'm with you, it is an ugly thing to create a
parent from the child...
Thanks
cghersi
On 30 Ago, 16:52, Frederik Pfisterer pfiste...@gmail.com wrote:
while if I understood your explanation I don't have to invoke
pm.makePersistent() on mySeconObject, is it?
- correct, it is automatically saved with the parent.
The other answer depends on the use case, but it appears to be very
bad style to produce an owner/parent in the child object... children
in real life also don't usually generate their parents ;-)
Fred
On 27 Aug., 16:03, cghersi cristiano.ghe...@gmail.com wrote:
Hi Frederik!
Sorry for my ignorance, I tougth that the right way to save a Second
object was:
pm.makePersistent(mySecondObject);
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
while if I understood your explanation I don't have to invoke
pm.makePersistent() on mySeconObject, is it?
I also put in all my getter methods a check on null object, in that
way:
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
�...@persistent
ListString tags;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
}
ListString getTags() {
if (tags==null)
tags= new ArrayListString();
return tags;
}
...
}
Do I have to remove all the check of the type if (obj==null)
obj=new...?
Thank you very much for your help!
Best
cghersi
On 27 Ago, 10:58, Frederik Pfisterer pfiste...@gmail.com wrote:
Hi,
the problem is this line:
owner = new First();
Beware that the only way you should ever store a Second object is:
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
since Second.owner is mapped it's automatically populated by the
persistance manager.
Hope this helps,
Fred
On 26 Aug., 17:38, cghersi cristiano.ghe...@gmail.com wrote:
Hi Diego,
thank you but unfortunately I strictly followed what stated in that
page, and the result is the problem I posted!!
Any other hint?
Thank you very much,
Best
Cghersi
On 26 Ago, 16:09, Diego Fernandes penet...@gmail.com wrote:
Hi,
i may find something
herehttp://code.google.com/intl/en/appengine/docs/java/datastore/relation...
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects,
so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this
[appengine-java] Re: JDO: Null parent on some children objects
while if I understood your explanation I don't have to invoke
pm.makePersistent() on mySeconObject, is it?
- correct, it is automatically saved with the parent.
The other answer depends on the use case, but it appears to be very
bad style to produce an owner/parent in the child object... children
in real life also don't usually generate their parents ;-)
Fred
On 27 Aug., 16:03, cghersi cristiano.ghe...@gmail.com wrote:
Hi Frederik!
Sorry for my ignorance, I tougth that the right way to save a Second
object was:
pm.makePersistent(mySecondObject);
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
while if I understood your explanation I don't have to invoke
pm.makePersistent() on mySeconObject, is it?
I also put in all my getter methods a check on null object, in that
way:
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
�...@persistent
ListString tags;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
}
ListString getTags() {
if (tags==null)
tags= new ArrayListString();
return tags;
}
...
}
Do I have to remove all the check of the type if (obj==null)
obj=new...?
Thank you very much for your help!
Best
cghersi
On 27 Ago, 10:58, Frederik Pfisterer pfiste...@gmail.com wrote:
Hi,
the problem is this line:
owner = new First();
Beware that the only way you should ever store a Second object is:
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
since Second.owner is mapped it's automatically populated by the
persistance manager.
Hope this helps,
Fred
On 26 Aug., 17:38, cghersi cristiano.ghe...@gmail.com wrote:
Hi Diego,
thank you but unfortunately I strictly followed what stated in that
page, and the result is the problem I posted!!
Any other hint?
Thank you very much,
Best
Cghersi
On 26 Ago, 16:09, Diego Fernandes penet...@gmail.com wrote:
Hi,
i may find something
herehttp://code.google.com/intl/en/appengine/docs/java/datastore/relation...
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects, so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this group, send email to
google-appengine-java+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: JDO: Null parent on some children objects
Hi,
the problem is this line:
owner = new First();
Beware that the only way you should ever store a Second object is:
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
since Second.owner is mapped it's automatically populated by the
persistance manager.
Hope this helps,
Fred
On 26 Aug., 17:38, cghersi cristiano.ghe...@gmail.com wrote:
Hi Diego,
thank you but unfortunately I strictly followed what stated in that
page, and the result is the problem I posted!!
Any other hint?
Thank you very much,
Best
Cghersi
On 26 Ago, 16:09, Diego Fernandes penet...@gmail.com wrote:
Hi,
i may find something
herehttp://code.google.com/intl/en/appengine/docs/java/datastore/relation...
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects, so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this group, send email to
google-appengine-java+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: JDO: Null parent on some children objects
Hi Frederik!
Sorry for my ignorance, I tougth that the right way to save a Second
object was:
pm.makePersistent(mySecondObject);
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
while if I understood your explanation I don't have to invoke
pm.makePersistent() on mySeconObject, is it?
I also put in all my getter methods a check on null object, in that
way:
class Second {
@Persistent
@PrimaryKey
Key id;
@Persistent
First owner;
@Persistent
ListString tags;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
}
ListString getTags() {
if (tags==null)
tags= new ArrayListString();
return tags;
}
...
}
Do I have to remove all the check of the type if (obj==null)
obj=new...?
Thank you very much for your help!
Best
cghersi
On 27 Ago, 10:58, Frederik Pfisterer pfiste...@gmail.com wrote:
Hi,
the problem is this line:
owner = new First();
Beware that the only way you should ever store a Second object is:
myFirstObject.getList().add(mySecondObject);
pm.makePersistent(myFirstObject);
since Second.owner is mapped it's automatically populated by the
persistance manager.
Hope this helps,
Fred
On 26 Aug., 17:38, cghersi cristiano.ghe...@gmail.com wrote:
Hi Diego,
thank you but unfortunately I strictly followed what stated in that
page, and the result is the problem I posted!!
Any other hint?
Thank you very much,
Best
Cghersi
On 26 Ago, 16:09, Diego Fernandes penet...@gmail.com wrote:
Hi,
i may find something
herehttp://code.google.com/intl/en/appengine/docs/java/datastore/relation...
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects, so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this group, send email to
google-appengine-java+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: JDO: Null parent on some children objects
Hi,
i may find something here
http://code.google.com/intl/en/appengine/docs/java/datastore/relationships.html
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects, so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this group, send email to
google-appengine-java+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
[appengine-java] Re: JDO: Null parent on some children objects
Hi Diego,
thank you but unfortunately I strictly followed what stated in that
page, and the result is the problem I posted!!
Any other hint?
Thank you very much,
Best
Cghersi
On 26 Ago, 16:09, Diego Fernandes penet...@gmail.com wrote:
Hi,
i may find something
herehttp://code.google.com/intl/en/appengine/docs/java/datastore/relation...
[]'s
Diego
On 26 ago, 04:42, cghersi cristiano.ghe...@gmail.com wrote:
Hi everybody,
I'm struggling with a strange problem with JDO.
I've got two PersistenCapable classes, one having a Collection of
objects of the second, something like this:
class First {
�...@persistent
�...@primarykey
Long id;
�...@persistent(mappedby=owner)
ArrayListSecond list = new ArrayListSecond();
ArrayListSecond getList() {
if (list == null)
list=new ArrayListSecond();
return list;
}
...
}
class Second {
�...@persistent
�...@primarykey
Key id;
�...@persistent
First owner;
First getOwner() {
if (owner==null)
owner = new First();
return owner;
...
}
In another class I need to print the owner of all my First objects, so
I do:
First obj = ...;
ArrayListSecond list = obj.getList();
for (Second s : list) {
System.out.println(s.getOwner());
}
In this loop, I find some Second object having null owner, and I
cannot understand why.
Now I have several questions about my data modelling:
1) Do I need to mark any field with (defaultFetchGroup = true)
annotation?
2) Does the check on null object (e.g. if (owner==null) owner = new
First();) in the getter methods results in any strange behavior?
3) Does the assignment on definition of objects (e.g.
ArrayListSecond list = new ArrayListSecond();) results in any
strange behavior?
4) Do I need to add any other annotation to owner field of Second
class?
Thank you very much for your help!!
Best regards
cghersi
--
You received this message because you are subscribed to the Google Groups
Google App Engine for Java group.
To post to this group, send email to google-appengine-j...@googlegroups.com.
To unsubscribe from this group, send email to
google-appengine-java+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
